Department: Vision Science ![[clear]](close-x.png "Remove this limiter")
49 matches in the database.
These are records: 1 - 30.
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1.
Atterholt, Nathan L.
The Effect of Stride Length on Ocular Tracking of Pitched Balls.
Degree: MS, Vision Science, 2011, Ohio State University
► The purpose of this study was to determine the amount of head…
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▼ The purpose of this study was to determine the amount of head movement associated with different batter stride lengths, and to determine if the longer stride leads to poorer pitch tracking. Coaches often disagree whether a stride is necessary when hitting, but if they do think a stride is necessary, almost all agree that the stride should be short. They justify this claim because of the presumed negative effect on gaze error associated with a long stride. We hypothesized that when a subject made a long stride toward the pitcher there would be significantly larger amounts of head rotation and translation. Fourteen subjects with a minimum of one year of high school baseball experience were enrolled in this study. They were tested using a pitching machine called the Flamethrower under three conditions. In the control condition they just tracked the ball, in the stride condition they made a stride of eight inches toward the pitching machine with their front foot, and in the no stride condition they raised their foot and then replaced it in the same location. Each subject viewed 100 pitches at a speed of approximately 80 miles per hour for each of the three conditions. The balls were pitched from a distance of 43.57 feet from the plate. Eye movements were recorded with the ISCAN infrared eye tracker. Head rotation and translation was recorded using the 3DM-GX1 Microstrain gyro head tracker and the Flock of Birds head tracker. Using a software program, head and eye recordings were synchronized. A total of 2300 pitches were analyzed and the mean absolute gaze errors, head movements, and eye movements were calculated. Mean absolute gaze errors were very similar initially for each of the three conditions. After 250 ms, the no stride condition exhibited a significantly larger gaze error, but gaze errors and standard deviations were very large in all conditions after 250 ms. Head rotation measured with the Microstrain tracker was initially (at 150 ms) significantly larger for the stride condition, but after 150 ms there was not a significant difference between the conditions. There was a tendency for larger head translations toward the pitching machine to occur in the stride condition. Combining the correlation analysis with the visual graph inspection, these data suggest that a horizontal rotation in the direction of the ball is accompanied by a concomitant horizontal translation in the direction of the ball. Eye movements were initially larger in the stride condition, but after 150 ms the stride and no stride condition were very similar. Both conditions exhibited larger eye movements than the track only control condition. Overall, tracking performance was not significantly different for subjects who took a stride when compared to subjects who just tracked the ball or subjects who used the no stride hitting approach. The absolute gaze errors were less than 2.5 degrees for the first 250 ms of the pitch for all conditions. After 250 ms, the gaze errors and standard deviations become quite large. Both translational and rotational head movements were similar between the three conditions and it can be concluded from this study that taking a stride does not lead to more head movement as was predicted by many coaches. Eye movement was also very similar between the no stride and stride conditions, although the track only condition did exhibit smaller eye movements. This indicates that taking a stride does not lead to increased eye movement which was also predicted by many coaches. From this study, it is reasonable to conclude that taking a stride does not significantly impact tracking a pitched ball. A stride also does not cause a batter to have excessive head and eye movements. It is quite possible that the stride can serve as an important timing mechanism of the swing. This study does not indicate which approach is better, but it does show that a stride is not detrimental for successful tracking.
Advisors/Committee Members: Fogt, Nicklaus.
Subjects: Ophthalmology; Optics
Keywords: baseball; ocular tracking; gaze; gaze error; stride; pitch
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2.
Bastian, Philip Nathan Jr.
The Central and Peripheral Physiological Response of the Cornea to Three Hydrogel Contact Lens Diameters.
Degree: MS, Vision Science, 2012, Ohio State University
► Purpose: The purpose of this study is to compare the physiological response…
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▼ Purpose: The purpose of this study is to compare the physiological response of the cornea to three hydrogel contact lens diameters. Methods: Fifteen subjects were fitted with three diameters (13.0, 14.0, and 15.0 mm) of Alden Classic hydrogel contact lenses (38% water content, dK 9.0). Lenses had a back vertex power of -3.00 D, center thickness of 0.1 mm, and base curve radius fitted according to guidelines using flat keratometry reading and lens diameter. Corneal oxygen uptake rates were measured at the central and peripheral cornea for the normal open eye and following 5 minutes of contact lens wear under both static (without blinking) and dynamic (with blinking once every 5 seconds) wearing conditions for each lens diameter. Oxygen uptake rates for each lens/condition were averaged between the two measurement sessions and then divided by those of the normal open eye obtained at the same location. Results: Corneal oxygen uptake rates increased with increasing lens diameter (p=0.006) regardless of location (central or peripheral) or condition (static or dynamic). The mean oxygen update relative to air was 4.59 (std=0.8) for the 13mm lens, 4.99 (std=1.4) for the 14mm lens, and 5.03 (std=0.9) for the 15mm lens. For all lens diameters, uptake relative to air was higher under static conditions (mean=5.18, std=1.2) compared to dynamic conditions (mean=4.56, std=0.7, p=0.001). Oxygen uptake relative to air was higher in the periphery (mean=4.95, std=0.9) compared to the central cornea (mean=4.79, std=1.2, p=0.011). Conclusions: Contact lens diameter does impact oxygenation of the central and peripheral cornea for Alden Classic hydrogel contact lenses.
Advisors/Committee Members: Fink, Barbara.
Subjects: Ophthalmology
Keywords: corneal oxygen uptake, hydrogel, lens diameter
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3.
Berntsen, David A.
Accommodative lag, peripheral aberrations, and myopia in children.
Degree: PhD, Vision Science, 2009, Ohio State University
► A two-year, double-masked, randomized clinical trial of myopic children 6 to 11…
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▼ A two-year, double-masked, randomized clinical trial of myopic children 6 to 11 years old is being conducted using progressive addition lenses (PALs) to evaluate two theories of juvenile-onset myopia progression. Eligible children had a high accommodative lag and either: (1) low myopia (less myopic than –2.25 D spherical equivalent) or (2) high myopia (more myopic that –2.25 D spherical equivalent) with esophoria at near. The accommodative lag theory hypothesizes that hyperopic retinal blur drives myopia progression. The mechanical tension theory hypothesizes that ciliary-choroidal tension created by the ocular components restricts equatorial expansion and causes axial elongation in people with factors that produce a large globe. To test between these theories, children were randomly assigned to wear either PALs with a +2.00-D add or single vision lenses (SVLs) for one year to achieve a reduction in myopia progression in the PAL group relative to the SVL group. All children then wear SVLs for the second year to evaluate the permanence of the treatment effect; a maintained treatment effect supports the lag theory, while a rebound supports mechanical tension. The primary outcome is central cycloplegic autorefraction. Complete ocular biometric data are being collected at six-month intervals. Over 17 months, 192 children were screened, and 85 (44%) were eligible and enrolled. The mean age (± SD) was 9.3 ± 1.4 years. The mean accommodative lag was 1.71 ± 0.37 D, and 54 children (64%) were esophoric at near. The mean cycloplegic spherical equivalent refractive error and axial length were –1.95 ± 0.78 D and 24.17 ± 0.80 mm, respectively. Baseline characteristics of the children enrolled are described. Because the clinical trial is ongoing, all findings are confidential. Aberrometry-based relative peripheral refraction measurements were validated against measurements made with an autorefractor. A method of analyzing peripheral aberration data collected from a dilated pupil was validated. A single-value metric of image quality was calculated to describe retinal image quality centrally and in four peripheral locations. When including only higher-order aberrations, image quality was best centrally and decreased in the periphery. When relative peripheral refractive error was included with higher-order aberrations, more significant reductions in peripheral retinal image quality were present, and the greatest reductions were in the temporal and superior retina where astigmatism was highest. Baseline and six-month accommodative lag data from children in the study were analyzed. Children still had a significant lag of accommodation for a 4-D stimulus when tested wearing a +2.00 D bifocal add. No evidence of an effect of bifocal adaptation on accommodative lag was found. Children with greater myopia progression over the previous six months exhibited higher accommodative lags when tested with their full manifest correction. Myopia progression had no effect on accommodative lag when testing was performed with the child’s habitual correction. These data suggest that a child’s accommodative lag should be measured with both the full manifest and habitual corrections if attempting to relate the retinal blur experienced by the child to his or her myopia progression.
Advisors/Committee Members: Zadnik, Karla.
Subjects: Optics
Keywords: juvenile-onset myopia, relative peripheral refraction, peripheral aberrations, accommodative lag, bifocal, progressive addition lens, image quality
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4.
Blacker, Adam Bryce.
Development of a Questionnaire to Measure Spectacle Dependence.
Degree: MS, Vision Science, 2009, Ohio State University
► There have been numerous attempts in vision science to ascertain information through…
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▼ There have been numerous attempts in vision science to ascertain information through the use of a survey or questionnaire. Questionnaires need to be accurate and efficient in order to gather reliable information. In the present study, 31 subjects were recruited to take two surveys (the National Eye Institute Refractive Error Quality of Life (NEI-RQL-42) questionnaire and an original spectacle use and dependence questionnaire) at their first visit, then again at their second visit two weeks later. Between visits, subjects had their spectacles fitted with a temperature sensor to monitor spectacle wear. Data from the surveys for the two visits and data from the temperature sensors were compared using Bland-Altman analyses for repeatability and agreement. Analyses were performed to also assess the effect that the comfort or awareness of the temperature sensor strap had on the responses to the spectacle use and dependence questionnaire. When the responses to the spectacle use and dependence questionnaire from both visits were compared, some subjects provided inconsistent responses regarding how many hours they wear their spectacles. In addition, some subjects’ responses did not agree well with the data gathered from the temperature sensors. It was unclear if the comfort of the temperature sensor strap impacted the responses to the survey. Although spectacle dependence is a very important measurement, obtaining accurate data may be more difficult than anticipated.
Advisors/Committee Members: Bailey, Melissa.
Subjects: Ophthalmology
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5.
Burcham, Marc A.
Suppression of the Rotational Vestibulo-Ocular Reflex during a Baseball Pitch.
Degree: MS, Vision Science, 2010, Ohio State University
► The purpose of this experiment was to determine to what extent individuals…
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▼ The purpose of this experiment was to determine to what extent individuals could cancel the rotational vestibulo-ocular reflex (RVOR) in order to track an accelerating, high speed ball. More specifically, this study was designed to determine if subjects could successfully track a baseball pitch while viewing the ball through small apertures. While wearing these aperture goggles, we hypothesized that the batsmen would have to increase the rotational amplitude of their heads while successfully suppressing their rotational vestibulo-ocular reflex in order to accurately track a pitched baseball. Subjects were tested using a pitching machine called the Flamethrower under normal viewing conditions (no apertures), then while wearing apertures that subtended 3.3 degrees of visual field, and finally under normal viewing conditions again. In the final trial (normal viewing), subjects were encouraged to replicate the eye and head movements adopted while wearing the apertures. Tennis balls were pitched from a distance of 44 feet from the batter at a measured velocity of approximately 80 miles per hour. Eye movements were recorded with the ISCAN infrared eye tracker and horizontal head rotations were recorded with the 3DM-GX1 head tracker. All head and eye recordings were temporally synchronized with each other and with ball position using software. A total of twelve subjects were enrolled in the study. Each subject viewed 50 pitches under each of the above defined testing conditions. A total of 1796 pitches were successfully recorded with nine subjects identified as able to accurately track a tennis ball under all testing conditions. Thus, 1346 pitches were analyzed. Mean gaze errors for all three trials indicated that the subjects were able to accurately track the pitched tennis balls for a majority of the ball’s flight path under each testing condition. Absolute gaze errors were smallest with the apertures compared to the other conditions at 300, 305, and 339ms after the pitch was released. These results were all statistically significant. The results of the study revealed consistent statistically significant differences in head movement when wearing the apertures at 200, 250, 300, 305, and 339ms. Specifically, this analysis revealed that the introduction of the apertures resulted in a decrease in head rotation. Finally, examination of the individual data suggested that in most cases once the aperture was removed, individuals generally did not completely adopt the same eye movements and head movements that had been used with the apertures. Overall these results suggest that wearing the aperture goggles aided in proper tracking. The improvement in gaze tracking with the apertures indicates that subjects could successfully cancel the RVOR. Further, the apertures generally resulted in a decline in head movement amplitude, in agreement with a previous study showing that individuals tend to show head movement overshoots when aiming the head at moving targets unless provided with a visual cue to head position. Further studies need to be performed to investigate any potential of the apertures to produce behavioral changes post training, and to determine whether these changes in eye and head coordination correlate with batting performance.
Advisors/Committee Members: Fogt, Nicklaus.
Subjects: Experiments
Keywords: vestibulo-ocular; RVOR; baseball tracking; apertures
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6.
Colling, Amber J.
A comparison of three methods of measuring central corneal thickness in normal and thinned corneas.
Degree: MS, Vision Science, 2010, Ohio State University
► The thickness of the cornea is an important parameter in Goldmann applanation…
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▼ The thickness of the cornea is an important parameter in Goldmann applanation tonometry, corneal disease, contact lens wear, and refractive surgery. Pachymetry is the measurement of corneal thickness, and currently ultrasound pachymetry is the gold standard. Several non-contact instruments, the Orbscan II (Orbtek, Inc.) and the Visante anterior segment-optical coherence tomographer (Carl Zeiss Meditec) have been introduced that provide more information about the cornea including corneal thickness topography maps. The goal of the present study was to determine repeatability of the instruments, to assess agreement between the instruments, and to assess the effect of corneal thickness on repeatability and agreement. Because each instrument is based on different principles, measurements may be biased when normal versus abnormally thin corneas are measured. Forty-five subjects (15 normal, 15 post-LASIK, and 15 keratoconus) were examined on two occasions, separated by one-to-seven days. Three measurements (later averaged) were made on the right eye of each subject using the three techniques. The subjects were analyzed as three groups: normal corneas, post-LASIK and keratoconus. Mixed model analysis of variance was used to compare between instruments, visit, and within groups. For each technique and cornea type, the difference between instruments and visits was determined for each subject and analyzed using Bland-Altman analysis to produce the mean, standard deviation, and 95% limits of agreement (LoA). A paired two-sample t test was also conducted for validity and repeatability. For normal corneas, mean central corneal thickness was as follows: 550 ± 34 µm for ultrasound, 541 ± 44 µm for Orbscan II, and 532 ± 38 µm for Visante. For post-LASIK corneas, mean central corneal thickness was as follows: 502 ± 40 µm for ultrasound, 495 ± 52 µm for Orbscan II, and 485 ± 42 µm for Visante. For keratoconic corneas mean central corneal thickness was as follows: 529 ± 46 µm for ultrasound, 498 ± 44 µm for Visante, and 490 ± 53 µm for Orbscan II. Mixed model analysis showed a significant interaction between instrument and cornea types (p=0.012). That is, the instruments not only measured significantly different from each other (p < 0.001) but also significantly different when measuring the various cornea types. Repeatability was poorer for all techniques in the keratoconic corneas and for ultrasound. For normal corneas, the Visante was the most repeatable: 95% LoA of –8 to +8 µm followed by the Orbscan: 95% LoA of –11 to +12 um, and ultrasound: 95% LoA of –15 to +19 um. For post-LASIK corneas, the Orbscan was the most repeatable: 95% LoA –11 to +11 µm followed by the Visante: 95% LoA of –10 to +13, and ultrasound: 95% LoA –24 to +16 um. For keratoconic corneas, the Visante was the most repeatable: 95% LoA –36 to +37 µm followed by the Orbscan: 95% LoA –31 to +47 µm and ultrasound: 95% LoA –40 to +53 um.
Advisors/Committee Members: Bullimore, Mark.
Subjects: Ophthalmology
Keywords: cornea; pachymetry; LASIK; keratoconus
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7.
Conrad, Joseph Samuel.
Vision Therapy for Binocular Dysfunction Post Brain Injury.
Degree: MS, Vision Science, 2011, Ohio State University
► PURPOSE: To prospectively evaluate the effectiveness of home-based computer vergence therapy for…
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▼ PURPOSE: To prospectively evaluate the effectiveness of home-based computer vergence therapy for treatment of binocular vision disorders in adults, ages 18-85, at least 3 months post brain injury. METHODS: Eligibility criteria included presence of binocular or accommodative dysfunction characterized by receded near point of convergence (NPC) (greater than or equal to 6 cm break), insufficient positive fusional vergence (PFV) at near (failing Sheard’s criterion or less than 15Δ blur or break), insufficient negative fusional vergence (NFV) at near (less than 12Δ blur or break), reduced vergence facility with 12ΔBO/3ΔBI at near (less than 15 cpm), and/or below minimum expected amplitude of accommodation for age. All subjects were prescribed 12 weeks of home-based computer vergence therapy. Phoria (cover test), NFV at near, PFV at near, NPC, vergence facility, accommodative amplitude and facility (nonpresbyopes only), and symptoms (convergence insufficiency symptom survey [CISS]) were assessed at baseline and after 4, 8 and 12 weeks of prescribed therapy. ANOVA was used to evaluate change in each measure. Percent successful also was determined. RESULTS: Of the 19 subjects enrolled (mean age 45.4 ± 12.9 years), 15 suffered external mechanical trauma to the head, 3 suffered cerebrovascular accident, and 1 suffered from organic brain syndrome. Six subjects were lost to follow-up. The binocular profile of the cohort at baseline was orthophoria (SD=1.08) at distance, 7.11Δ (SD=5.19) exophoria at near, NPC break = 17.07 cm (SD=10.56), NPC recovery = 21.48 cm (SD=11.66), near NFV = 12.33Δ (SD=4.37), near PFV = 8.80Δ (SD=5.69), vergence facility = 4.06 cpm (SD=4.41), and CISS = 31.12 (SD=12.93). ANOVA showed statistically significant improvement for NPC break (p=0.002) and recovery (p less than .001), PFV blur (p less than .0001), break (p less than .0001), and recovery (p less than .0001), NFV blur (p=0.047), break (p=0.008), and recovery (p=0.017), vergence facility (p less than .0001), and CISS (p less than .0001). The percentage of patients who were classified as “successful” or “improved” was 69% for NPC (less than 6 cm or a decrease of greater than 4 cm), 77% for PFV (greater than 15Δ and passing Sheard’s criterion or an increase of greater than or equal to 10Δ), 77% for NFV (greater than or equal to 12Δ or an increase of greater than or equal to 6Δ), 69% for PFV and NFV, 92% for vergence facility (15 cpm or an increase of 3 cpm), and 62% for CISS (less than 21 or a decrease of greater than or equal to 10 points). CONCLUSIONS: The majority of the 68% of subjects who completed the study experienced meaningful improvements in signs and symptoms.
Advisors/Committee Members: Taylor Kulp, Marjean.
Subjects: Ophthalmology; Optics; Rehabilitation
Keywords: vision therapy, brain injury, binocular vision, convergence insufficiency
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8.
DeCock, Candace Eva.
Vision with Spectacles in Keratoconus.
Degree: MS, Vision Science, 2009, Ohio State University
► Purpose: The vision in keratoconus is most often best corrected with rigid…
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▼ Purpose: The vision in keratoconus is most often best corrected with rigid gas permeable lenses, and patients with keratoconus often rely on contact lenses as their primary means to clear vision. In cases of lost contact lenses or anterior segment disease that requires the cessation of contact lens wear, these patients are often left without a viable means of vision correction. The purpose of this study is to determine if “back-up” spectacles could provide adequate vision for keratoconus patients in times of contact lens cessation. Methods: Eleven participants were prescribed spectacles and completed two examinations in this study. High and low contrast Bailey-Lovie visual acuity was measured with the participants’ habitual contact lenses and manifest refraction was performed at examination one. High and low contrast Bailey-Lovie visual acuity was measured with the spectacles prescribed in the study and a repeat manifest refraction was performed at examination two. Slit lamp biomicroscopy, keratometry, and automated topography using the Atlas topographer was also performed at both examinations. Participants wore their contact lenses from morning to 6:00 p.m. and their spectacles from 6:00 p.m. to bedtime on Day 1 and Days 3-6 of the study. Spectacles only were worn on Day 2 of the study. Participants completed a patient log during the study to record their experiences with glasses wear. Results: High contrast visual acuity for manifest refraction between examination one and examination two dropped an average of 1.8 ± 4.1 letters both eyes together, dropped by an average of 1.0 ± 4.6 letters for the “worse eyes,” and dropped by an average of 2.4 ± 5.7 letters for the “better eyes.” The average number of hours that the glasses were worn was 6.35 ± 3.80 hours for Days 1 and Days 3-6 of the study and 13.94 ± 4.44 hours for Day 2 of the study. Participants rated that vision in the glasses was slightly worse than vision in the contact lenses on average. The most common subjective visual response reported by the participants was Positive Adaptation. Conclusions: If proper expectations regarding visual performance are put into place by the eye care practitioner prior to spectacle use, keratoconus patients may be successful with “back-up” spectacles in circumstances that require the cessation of contact lenses.
Advisors/Committee Members: Zadnik, Karla.
Subjects: Ophthalmology
Keywords: keratoconus, spectacles
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9.
Ernst, Lauren E.
Ciliary Body Thickness and the Relationship to Refractive Error and Accommodative Function in Adults.
Degree: MS, Vision Science, 2010, Ohio State University
► The purpose of this study was to determine the relationships among ciliary…
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▼ The purpose of this study was to determine the relationships among ciliary body thickness, anterior scleral thickness, accommodative lag, and refractive error in adults as well as the difference between nasal and temporal ciliary body thickness. Subjects with varying refractive error (range: -11.03 to +3.13 D) were recruited. Cycloplegic refractive error, axial length, accommodative lag (4.00-D stimulus), and ciliary body thickness (CBT2, CBT3) and anterior scleral thickness (AST2) at 2 and 3 mm posterior to the scleral spur were measured. Repeated measures regression models were used to define the relationship between CBT2, CBT3 and refractive error, axial length, or accommodative lag, and also AST2 and refractive error or axial length. A Bland-Altman analysis was utilized to determine the difference between nasal and temporal ciliary body thickness. The relationships between CBT2 and CBT3 and refractive error were statistically significant (p = 0.04 and 0.02 respectively). The relationships between CBT2 and CBT3 and axial length were statistically significant (p = 0.01 and 0.002 respectively). No relationship was found between AST2 and refractive error or between AST2 and axial length (all p > 0.05). The relationship between ciliary body thickness and accommodative lag was not significant at any measurement point. The ciliary body was thicker in patients with increasing myopia and increasing axial lengths. Further studies are needed to determine if thicker ciliary bodies are related to the etiology of myopia and to determine if differences in the etiology exist for low-to-moderate myopia as opposed to high myopia.
Advisors/Committee Members: Bailey, Melissa.
Subjects: Ophthalmology
Keywords: myopia; ciliary body; refractive error
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10.
Fadel, Haind Mosbah Noraden MD.
Correlation Between AC/A Ratio and Ciliary Muscle Morphology in School-Age Children.
Degree: MS, Vision Science, 2011, Ohio State University
► Purpose: To examine how the morphology of the ciliary muscle varies as…
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▼ Purpose: To examine how the morphology of the ciliary muscle varies as a function of AC/A ratio and to investigate the difference between the thickness of the ciliary muscle during accommodation and during cycloplegia. Methods: Measurements were performed on the right eye only of thirty children aged 6 to 12 years. Height and weight were measured. Accommodative response was measured by autorefraction through habitual correction. Axial length was measured with the IOLMaster. Temporal ciliary muscle images from anterior segment Vistante OCT at 1mm (CMT1), 2mm (CMT2), and 3mm (CMT3) posterior to the scleral spur at 0D and 4D stimulus levels and under cycloplegia were measured four times each. Accommodative response and pupil size data were simultaneously recorded by the PowerRefractor during ciliary muscle measurements. Result: There were no significant correlations between AC/A ratio and the changes in ciliary muscle thicknesses, CMT1 (P= 0.8), CMT2 (P= 0.8), CMT3 (P=0.9), or CMT MAX (P=0.9). Axial length has an inverse correlation with the changes in ciliary muscle thicknesses at CMT1 (P=0.004), CMT2 (P=0.04), and CMT MAX (P= 0.03), but not with CMT3 (P= 0.07). However, when the extreme changes in CMT measures were removed, there was not a significant correlation with axial length at any location. Age was not significantly correlated with changes in CMT1 (P=0.18), CMT2 (P=0.4), CMT3 (P=0.5), or CMT MAX (P= 0.4). Conclusions: The AC/A ratio did not appear to be significantly correlated with the changes in ciliary muscle thicknesses with accommodation in this study. Increased axial length was correlated with thinning of the ciliary muscle, possibly due to the positive correlation between axial length and ciliary muscle thickness. Further investigation is necessary to determine whether the association truly exists and the potential reason for the relationship.
Advisors/Committee Members: Bailey, Melissa.
Subjects: Ophthalmology; Optics
Keywords: AC/A ration, accommodation, ciliary muscle
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11.
Gowrisankaran, Sowjanya.
Influence of Sustained Vergence and Accommodative Convergence on Disparity Detection.
Degree: PhD, Vision Science, 2009, Ohio State University
► The ability to detect absolute disparity can be assessed by studying the…
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▼ The ability to detect absolute disparity can be assessed by studying the depth perception or vergence eye movement responses to briefly flashed (200 msec) disparity stimuli. It has been previously shown that sustained convergence influences the vergence dynamics to subsequently flashed convergent disparities. Another factor that has been suggested to have an influence on vergence dynamics, is accommodation. Changes in vergence dynamics could have resulted from modifications at the level of the disparity detectors, vergence burst cells or at the level of the extraocular muscles. Two experiments were conducted to test the hypothesis that sustained vergence and accommodative convergence could have a potential influence on the response behavior of disparity detectors, which results in changes to perceived depth from convergent and divergent horizontal disparities. Experiment 1 was performed to study the effect of sustained vergence on depth perception from horizontal disparity targets. Twenty subjects were recruited. Depth perception to briefly flashed (200 msec) convergent and divergent disparity targets were assessed before and after a period of sustained vergence either at a +4 degree, -4 degree or a 0 degree demand with respect to a fixation distance of 50 cm. Repeated measures ANOVA was performed on data from 19 subjects. Results indicate that the ability to detect depth from convergent disparities was significantly influence by sustained vergence demand (p=0.04). Depth perception from convergent disparities was increased following sustained divergence and decreased following sustained convergence. There was no significant effect of sustained vergence on depth perception from the divergent disparity targets. Phoria adaptation following sustained vergence did not have a statistically significant effect on depth perception from convergent or divergent disparity targets (p=0.08). In experiment 2, twenty one subjects were recruited. Subjects fixated on target at different fixation distances (45, 60 and 100 cm) for 6 sec, following which briefly flashed (200 msec) disparity targets were presented either with a convergent, divergent or zero demand with respect to fixation. Target for fixation was either an accommodative target or a Gaussian blob target presented in a randomized order. Repeated measures ANOVA was used to analyze the data. Results showed that the accuracy of depth perception decreased with closer fixation distances (p < 0.001) for divergent disparity targets. There was no significant effect of fixation distance on depth perception from convergent disparity targets. Accommodation did not influence the accuracy of depth perception either in the convergent or divergent directions. The results obtained for depth perception from crossed disparities is congruent with the results obtained previously for vergence dynamics to crossed disparities following sustained vergence. An increase in the effort required to sustain a convergence posture leads to improvements in convergent disparity detection. Even though previous work has shown influence of sustained vergence on divergence dynamics, depth perception results for divergent disparity were not in agreement with those results. Thus there might be a common pool of disparity detectors for depth perception and vergence eye movements at least for the crossed disparities whose response characteristics are modified following sustained vergence.
Advisors/Committee Members: Fogt, Nicklaus.
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12.
Graham, Nicholas Dale.
The Heritability of Refractive Error between Siblings.
Degree: MS, Vision Science, 2010, Ohio State University
► Refractive error is identified as the deviation from emmetropia that progresses either…
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▼ Refractive error is identified as the deviation from emmetropia that progresses either towards myopia or hyperopia. This phenotypic occurrence has been documented as being jointly due to genetics and the environment. This study looks to assess the contribution of heredity while considering the environment in refractive error development. Using data from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) study, there were 912 sibling pairs identified, ranging in age from 6 to 14 years, from various ethnic backgrounds. Linear regression analyses of the spherical equivalent and the ocular axial length were performed, controlling for age, while factoring in the environmental variables and ethnicity to determine their relevance. Heritability was calculated using the slope determined from the analyses of the spherical equivalent and axial length data of all available refractive errors. The heritability (h2) found from the spherical equivalent data for this total sample produced a genetic variance of 0.784 with a 95% confidence interval of 0.648 - 0.920 (78.4% with a 95% CI 64.8% – 92.0%). The heritability (h2) found from the axial length data for this total sample produced a genetic variance of 0.834 with a 95% confidence interval of 0.708 - 0.958 (83.4% with a 95% CI 70.8% – 95.8%). The best overall model determined from the greatest adjusted R square value for spherical equivalent was 0.146, and the best overall model for axial length resulted in an adjusted R square value of 0.175. Because of the shared genetics between siblings, a realistic R square value in this study’s would be 0.25, indicating that this model explains a reasonable portion of the variance of refractive error between siblings. The heritability values and ranges found confirm that genetics are significant in the development of a subject’s spherical equivalent and axial length. Controlling for the environment had little impact on the heritability values that were determined.
Advisors/Committee Members: Jones- Jordan, Lisa.
Subjects: Biomedical research; Genetics; Health education; Ophthalmology; Public health
Keywords: heritability; myopia; hyperopia; refractive error; siblings; environment; genetics; ethnicity; spherical equivalent; axial length; CLEERE
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13.
Greiner, Katie Lynn.
Quality of Life of Pediatric Bifocal Soft Contact Lens Wearers.
Degree: MS, Vision Science, 2009, Ohio State University
► One method being studied to slow myopia progression is the use of…
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▼ One method being studied to slow myopia progression is the use of distance center bifocal soft contact lenses. Animal studies show that the peripheral retina plays more of a role in regulating eye growth than was previously thought. They also show that it is myopic defocus that slows this eye growth. By using distance center bifocal soft contact lenses, the central portion of the lens provides good focus of light to the central retina. The peripheral part of the lens provides near vision with light focused in front ofthe peripheral retina thus creating myopic blur. This study is designed to determine if children can tolerate bifocal soft contact lenses in future treatments for myopia control. Typically, bifocal soft contact lenses tend to slightly compromise acuity in adult wearers because they correct two different ranges of vision. We want to find out if children are bothered by this and to make sure the pediatric subjects can tolerate constantly wearing a near add. Therefore, we are comparing the change in quality of life when children switch from spectacles to soft spherical contact lenses or bifocal soft contact lenses. Historical data for age-and gender-matched soft spherical contact lens wearers will be used for comparison between the two modalities. We fitted 27 pediatric subjects in bifocal soft contact lenses and administered the Pediatric Refractive Error Profile (PREP) for Glasses at their baseline visit and the PREP Survey for Contact Lenses at the 1 month visit. Previously, 27 control subjects completed the same surveys in the same time period while wearing soft spherical contact lenses instead. The PREP survey consists of 26 statements based on vision-related functioning and well-being in children with some level of refractive error. Scores are scaled from zero(poor quality of life) to 100 (good quality of life), and an overall PREP score is the mean score of all of the statements. Results from this survey allowed us to compare how overall composite scores and scale scores differed between spectacle and contact lens wearers as well as between soft contact lens and bifocal soft contact lens wearers. Our data suggest that children were tolerable of bifocal soft contact lenses. The overall composite score for the PREP showed an increase after one month of bifocal soft contact lenses wear (Student’s t test, p <0.001) and after soft contact lens wear (Student’s t test, p = 0.004). However, there was not a significant difference in the change from baseline to one month between soft bifocal and soft spherical contact lens wearers (Student’s t test, p 0.59). Mean scores for each scale of the PREP survey rose after one month of bifocal soft contact lens wear, with the greatest improvements in the scales of Satisfaction and Activities (Student’s t test, p < 0.005 for both). The quality of life changes with soft contact lenses were similar to the changes following bifocal soft contact lens wear, which shows that bifocal soft contact lenses are a viable option to test in future studies of myopia control in children.
Advisors/Committee Members: Walline, Jeffrey.
Subjects: Health; Optics
Keywords: contact lenses; pediatrics; bifocal soft contact lenses; quality of life survey for refractive error; myopia progression
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14.
Hager, Michele LynnManeca.
A Study of Contact Lens Comfort in Patients Wearing Comfilcon A Soft Contact Lenses Compared to Their Habitual Soft Contact Lenses.
Degree: MS, Vision Science, 2009, Ohio State University
► Contact lens discomfort, especially contact lens-related ocular dryness, is a major cause…
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▼ Contact lens discomfort, especially contact lens-related ocular dryness, is a major cause of contact lens wear discontinuation. Many studies have evaluated different contact lens materials for their comfort in both normal patients and sufferers of contact lens-related dry eye. This study seeks to evaluate a new silicone hydrogel soft contact lens material (comfilcon A) in terms of comfort, measurable tear film parameters, and total contact lens-extracted lipid in normal and contact lens-related dry eye contact lens wearers as compared to their habitual contact lenses. Thirty four participants completed this study consisting of two visits—the first with participant wearing their habitual soft contact lenses and the second with the study contact lenses. Interferometric measurements of the pre-lens tear film thinning rate (PLTF thinning rate), the lipid layer thickness (LLT), and the initial pre-lens tear film thickness (PLTF) were recorded, the Contact Lens Dry Eye Questionnaire (CLDEQ) was peformed, and the participants’ lenses were collected for lipid analysis at each visit. The CLDEQ scores at the first study visit of the non-dry eye and dry eye group were shown to be significantly different from one another (p <0.0001). Total extracted lipid amounts showed a significant difference for the non-dry eye group between the first and second study visits (p = 0.01) but not for the dry eye group (p = 0.10). A significant correlation was found between LLT and PLTF thinning rate for the first visit (r = 0.39, p = 0.03), but not for the second visit (r = 0.14, p = 0.43). A significant correlation was found between CLDEQ score and PLTF thinning rate for the dry eye group (rs = -0.55, p = 0.03) but not for the non-dry eye group (rs = 0.11, p = 0.71) at the first visit. A significant correlation was found between CLDEQ score and LLT for the non-dry eye group (rs = -0.53, p = 0.04) but not for the dry eye group (rs = -0.18, p = 0.53) at the first visit. A significant correlation was found between contact lens-extracted lipid quantity and number of days for which the habitual contact lenses were worn (r = 0.37, p = 0.03). One month of wear of comfilcon A silicone hydrogel contact lenses did not significantly improve subjective dryness symptom severity in either normals or contact lens-related dry eye sufferers as compared to their habitual lens materials. Further research is needed to determine a quantifiable tear film parameter or other marker by which to diagnose or grade contact lens-related dry eye and is also needed to find or develop a soft contact lens material that can be comfortably worn by contact lens-related dry eye sufferers.
Advisors/Committee Members: Nichols, Jason.
Subjects: Ophthalmology
Keywords: dry eye; comfilcon A; interferometry; lipid layer thickness; pre-lens tear film thinning rate; pre-lens tear film thickness; contact lens dry eye questionnaire
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15.
Harp, Lisa.
Contributions of Silicone Hydrogel Transmissibility and Tear Exchange to Corneal Oxygen Supply.
Degree: MS, Vision Science, 2010, Ohio State University
► Purpose: The purpose of this study is to evaluate the physiological performance…
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▼ Purpose: The purpose of this study is to evaluate the physiological performance of 4 silicone hydrogel contact lens and 2 rigid lens materials. The difference in corneal oxygen uptake measured under static and dynamic wearing conditions, which provides an indication of the amount of tear exchange that takes place with the blink, will be compared. Methods: Corneal oxygen uptake was measured on the right eye of 15 subjects after 5 minutes of static (no blinking) and dynamic (blinking every 5 seconds) wear of the following lens materials: Senofilcon A (Vistakon Acuvue Oasys, 14.0 mm diameter), Comfilcon A (Cooper Biofinity, 14.2 mm diameter), Silfilcon A (Ciba O2 Optics, 13.2, 14.0, and 14.8 mm diameters), Lotrafilcon (Ciba Night & Day, 13.8 mm diameter), Menicon Z (8.8 mm diameter), and polymethylmethacrylate (PMMA) (8.8 mm diameter). Measurements were relativized to those recorded with no lens and with the PMMA lens. Friedman’s test was used to compare the mean relativized data across the contact lens materials. Post-hoc comparisons were performed using the methods described by Conover to control the alpha level for multiple comparisons. Results: There were significant differences (p=0.019) in the difference values between static and dynamic condition data across lens materials/designs. The difference values, from highest to lowest, were associated with Ciba Night & Day, O2 Optics/14.0 diameter, O2 Optix/14.8 diameter, O2 Optix/13.2 diameter, Cooper Biofinity, Menicon Z, Acuvue Oasys. Conclusions: Corneal oxygen demand differences among contact lens materials and designs are related to both corneal oxygen dynamics (lens transmissibility) and tear exchange (influenced by lens design and modulus).
Advisors/Committee Members: Fink, Barbara.
Subjects: Ophthalmology; Philosophy
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16.
Haworth, Kristina Marie OD.
Examination of Human Meibum Collection and Extraction Techniques.
Degree: MS, Vision Science, 2009, Ohio State University
► Purpose: To compare various meibum collection methods and extraction techniques.Methods: Sixty subjects…
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▼ Purpose: To compare various meibum collection methods and extraction techniques.Methods: Sixty subjects were seen on two visits. Meibum was collected from the lower lid of the right eye with a glass microcapillary tube, and with a Dacron swab, cytology microbrush or spatula from the left eye. Extraction with 2:1 chloroform:methanol was done either immediately or after data collection was complete. Individual samples were divided into four equal aliquots for analysis of total lipids, cholesterol and inorganic phosphates via assay based techniques. Effects of collection method, extraction, and dry eye status were examined using repeated measures ANOVA and logistic regression. Mass spectrometry was used to evaluate for identification of lipid peaks typically found in human meibum for three representative samples from each collection technique group. Samples from nine normal subjects were selected for comparison, three from each of the three groups, and evaluated by mass spectrometric analysis. Each sample was analyzed with direct infusion electrospray time-of-flight mass spectrometry (Waters,Quadrupole-TOF II). Spectra obtained were examined for presence of nine peaks previously identified as typically in human meibum. Results: Total lipids showed an impact of collection device (p<0.0001), but not for extraction technique (p=0.13) or dry eye status (p=0.97). Dacron swab collection was associated with more total lipid on average than each other collection device (p<0.0001). The cholesterol assay showed an impact of collection device (p<0.0001) and extraction technique (p=0.0002), but not dry eye status (p=0.55). Spatula collection was associated with more cholesterol on average than each other collection device (p<0.0001). For inorganic phosphates, immediate extraction (p<0.0001), cytology microbrush collection(p<0.0001), and non-dry eye status (p=0.03) were associated with the greater likelihood of detection. Mass spectrometric analysis results varied by collection device. Wax esters (mass to charge ratio m/z 641.62, 655.64, and 669.65) were identified in samples collected by microcapillary tube (100%), cytology microbrush (78%), and spatula (100%). Cholesterol esters (m/z 759.68, 773.72, and 787.73) were identified in samples collected by microcapillary tube (100%), cytology microbrush (22%), and spatula (78%). Triacylglycerols (m/z 907.77) were detected in 100% of samples collected by microcapillary tube, cytology microbrush and spatula. Diesters (m/z 1031.97 and 1150.05) were detected in samples collected by microcapillary tube (89%), cytology microbrush (50%), and spatula (83%). None of the peaks were identified in samples collected by Dacron swab and significant plastic polymer was visible in the spectra, masking the signal from lipid peaks. Conclusions: Dacron swab collection was associated with the highest average amount of total lipid detected, whereas spatula collection and immediate extraction was associated with the highest average amount of cholesterol detected. Lastly, cytology microbrush collection with immediate extraction on non-dry eye subjects was associated with the highest probability of detection of inorganic phosphates. Microcapillary tube collection was associated with most frequent detection of each lipid class, with spatula collection a close contender. Dynamic range of the mass spectrometer was likely exceeded with resulting signal suppression by predominance of polymers in Dacron swab-collected samples, and to a considerable yet lesser degree with the cytology microbrush.
Advisors/Committee Members: Nichols, Kelly.
Subjects: Biochemistry
Keywords: lipids; human meibum; collection methods; extraction techniques; dry eye
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17.
Hinel, Erich Anthony.
The Use of Fluorescent Quenching in Studying the Contribution of Evaporation to Tear Thinning.
Degree: MS, Vision Science, 2010, Ohio State University
► Purpose: It is hypothesized that evaporation is the major mechanism of tear…
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▼ Purpose: It is hypothesized that evaporation is the major mechanism of tear film thinning between blinks. This can be demonstrated through the ‘self-quenching’ property of fluorescein. At low concentrations, fluorescent efficiency is independent of concentration, while at high concentrations, fluorescent efficiency falls rapidly. If tear film break up is due to evaporation, then at high concentrations, the measured fluorescein intensity will decay as the fluorescein becomes more concentrated within the tear film. The purpose of this study is to determine if tear film thinning corresponds with changes in the fluorescent intensity of fluorescein in the tears. Methods: Thirty subjects were recruited for this study (34.3 ± 13.1 years of age, 57% female). At baseline, 1µL of 2% fluorescein was placed in the right eye of each subject. Two concurrent 20 second open-eye spectral interferometer recordings, capable of measuring tear film thickness and fluorescein intensity, were obtained. Five minutes after the initial 2% drop instillation, 1 µL of 10% fluorescein was placed in the right eye of each subject. Two concurrent interferometry measurements were obtained. The fluorescein decay rate was compared to the tear film decay rate using nonparametric statistical analyses. Results: The mean fluorescent decay rate for the first trial of 10% fluorescein was 3.09% per second, while the second trial of 2% fluorescein decay rate was 0.50% per second. The difference between these two decay rates was significant (p < 0.0005, Wilcoxon Sign Rank). The difference in mean thinning rates for the first trial of the 10% fluorescein (1.83% per second) and second trial of the 2% fluorescein (1.58% per second) was not significant (p = 0.76, Wilcoxon Sign Rank). Conclusion: The significant difference in fluorescein decay observed between the 2% and 10% fluorescein trials provides further evidence that evaporation is the major mechanism contributing to tear film thinning between blinks.
Advisors/Committee Members: Nichols, Jason.
Subjects: Ophthalmology
Keywords: Dry Eye, Cornea, Fluorescein, Evaporation
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18.
Huang, Ching-Yao.
Measurement and Comparison of Progressive Addition Lenses by Three Techniques.
Degree: MS, Vision Science, 2011, Ohio State University
► Purpose. To measure and evaluate variations in spherical power, astigmatism and higher-order…
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▼ Purpose. To measure and evaluate variations in spherical power, astigmatism and higher-order aberrations (HOAs) in progressive addition lenses (PALs) by three techniques and to compare their differences. Methods. Two experiments are described. The first measured and evaluated the optical properties of six PALs with adds from +1.25 D to +2.75 D by the Hartmann-Shack aberrometry. The second experiment compared the Hartmann-Shack aberrometry with the other two methods: Moiré interferometry and surface profilometry, on five PALs (plano distance power, +2.00 D add) under the condition of lateral displacement of lens. A Hartmann-Shack wavefront sensor (HSWFS) on a custom-built optical bench was used to capture and measure the spatially resolved wavefront aberrations of PALs. A Rotlex Class Plus lens analyzer operating as a Moiré interferometer was used to measure the spherical and cylindrical powers of PALs. A coordinate measuring machine (CMM) was used to measure front and back surface heights of PALs which were converted to surface powers and compared with the two optical measurement methods. The measurement data from the HSWFS, Rotlex, and CMM methods were analyzed and compared using custom MATLAB programs in terms of spherical equivalent power (M), cylindrical power (J), and HOAs. Pupil sizes up to a maximum of 4.5 mm were possible with the HSWFS system. Matrix techniques were used to scale Zernike expansion coefficients to different pupil sizes. Color contour plots of M, J, and HOAs in all PALs were then generated. Results. As expected, in a typical PAL, spherical power increases along the progressive corridor, and unwanted astigmatism increases laterally from the vertical midline. Evaluation of six PALs from the HSWFS measurements indicates that the greater the add power, the greater the rate of power change and the unwanted astigmatism, but the narrower the progressive corridor width. Of the HOAs, 3rd order aberrations, coma and trefoil, are prominent at the progressive corridor area and around the near power zone. The impact of these HOAs is attenuated at smaller pupil sizes, which is consistent between the measurement and theoretical calculation. Comparison of three measurement methods shows good agreement for the optical properties of the five PALs. There are no meaningful differences in M and J among the HSWFS, Rotlex, and CMM methods. There are also no meaningful differences in the root mean square (RMS) of HOAs between the HSWFS and CMM methods. Conclusions. The HSWFS method shows great potential for the measurements of the optical properties of PALs. It demonstrates that higher add power is associated with higher rate of power change and higher unwanted astigmatism, but narrower progressive corridor width. The 3rd order aberrations dominate HOAs and occur along the corridor and around the near zone, and are greatly affected by the pupil size. Comparisons of spherical equivalent power, cylindrical power, and HOAs on PALs indicate that the non-optical method, CMM, can be used to evaluate the optical properties of a PAL through front and back surface height measurements. In conclusion, the three measurement methods, HSWFS, Rotlex, and CMM, are comparable.
Advisors/Committee Members: Bullimore, Mark A.
Subjects: Optics
Keywords: progressive addition lenses; ophthalmic optics; wavefront aberrations; Hartmann-Shack aberrometry; Moiré interferometry; surface profilometry; coordinate measuring machine; Rotlex; freeform; Zernike polynomials
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19.
Huston, Amanda K.
Screening of Children Study.
Degree: MS, Vision Science, 2012, Ohio State University
► PURPOSE: SureSight Vision Screener and Retinomax Autorefractor have been shown to be…
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▼ PURPOSE: SureSight Vision Screener and Retinomax Autorefractor have been shown to be effective screening tests for identification of significant refractive error in preschool children. The purpose of Screening of Children Study (SOCS) was to determine the effectiveness of SureSight Vision Screener and Retinomax Autorefractor in identifying significant refractive error in school-aged children. METHODS: SureSight and Retinomax were used to measure non-cycloplegic refractive error in children aged five to thirteen undergoing comprehensive eye examination including cycloplegic autorefraction. Significant cycloplegic refractive error as measured using the Canon RK-3 autorefractor was defined as: hyperopia greater than or equal to 2.75 diopters (D) in any meridian, myopia of more than 0.50 D in any meridian, astigmatism greater than or equal to 1.50 D between principal meridians, and anisometropia greater than or equal to 1.50 D difference in spherical equivalent (SEQ). The ability of SureSight and Retinomax to identify each type of refractive error was summarized by the area under the receiver operating characteristic curve (AUC) using all possible cut points for defining failure. Detection of refractive error was based on the child’s worse eye using the following SureSight or Retinomax results: most positive meridian for hyperopia, most negative meridian for myopia, cylinder for astigmatism, and difference in SEQ for anisometropia. RESULTS: One hundred and ninety-five subjects, mean age 9.35 +/- 2.33 years, completed the study. Criteria for significant refractive error were met by 37 children for hyperopia, 87 for myopia, 52 for astigmatism, and 12 for anisometropia. Using SureSight, AUC was 0.89 (95% CI 0.84-0.95) for detection of hyperopia, 0.86 (0.81-0.91) for detection of myopia, 0.95 (0.91–0.99) for detection of astigmatism, and 0.82 (0.65–0.98) for detection of anisometropia. Using Retinomax, AUC was 0.96 (0.91–1.00) for detection of hyperopia, 0.85 (0.79–0.90) for detection of myopia, 0.95 (0.91–0.99) for detection of astigmatism, and 0.86 (0.73–0.99) for detection of anisometropia. Effectiveness of the two instruments was not statistically significantly different for detection of any type of significant refractive error. CONCLUSION: AUC was very good to excellent for detection of each type of significant refractive error using SureSight Vision Screener and Retinomax Autorefractor in school-aged children.
Advisors/Committee Members: Kulp, Marjean Taylor.
Subjects: Health Care; Ophthalmology; Public Health
Keywords: Vision Screening; Pediatric Optometry
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20.
Kimball, Samuel H.
Evaporation is the Primary Mechanism of Tear Film Thinning.
Degree: MS, Vision Science, 2009, Ohio State University
► The purpose of this study was to determine the contribution of evaporation…
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▼ The purpose of this study was to determine the contribution of evaporation in the thinning of the pre-corneal tear film. The human tear film is essential to the optical and physiological function of the eye. A malfunctioning tear film can be visually disruptive as well as cause damage to the ocular surface. Dry eye disease is an ocular surface disorder that is essentially a manifestation of a faulty tear film. Dry eye disease represents a significant public health concern and a better understanding of the mechanisms involved in the eradication of the tear film will be needed in order to better treat and manage this significant disease. There are three possible mechanisms of tear film thinning and they include absorption (inward flow), tangential flow, and evaporation (outward flow) of the tears. Previous research, designed to establish the contribution of each of the three proposed mechanisms of tear film thinning, has led to disagreement as to the significance of evaporation or outward flow in the thinning of the human tear film. This study was designed to discover the contribution of evaporation in the thinning of the pre-corneal tear film. Tear thickness values and tear film thinning rates were gathered using spectral interferometry from the right eye of 39 subjects with a mean age of 30.0 ± 9.5 years. Tear film data was gathered under two differing conditions for each subject: open-air and airtight goggles. Two separate recordings of the tear film were first made given the open-air condition then two recordings were made for subjects wearing the airtight goggles. Each subject also completed an Ocular Surface Disease Index (OSDI) questionnaire. Data analysis revealed that the mean initial thickness for subjects under open-air conditions was 3.46 ± 0.83 µm compared to 3.54 ± 0.83 µm for subjects wearing goggles (p = 0.53). The mean tear film thinning rate for subjects in open-air was 3.53 ± 4.12 µm/min and -0.16 ± 1.78 µm/min for the same subjects wearing airtight goggles. The mean OSDI score was 10.8 ± 7.1, with four subjects being classified as dry eye (OSDI > 22). A significant reduction in the tear film thinning rate is seen when evaporation is controlled with airtight swimming goggles. In fact on average the tear film thinning rate is reduced to nearly zero when simulating a non-evaporative environment. This suggests that evaporation is the primary means by which the tear film thins. The reason for the contradictory evidence put forth in the literature concerning the contributions of the three proposed mechanisms of tear film thinning may be explained by the difference in testing methodology. It appears conclusive from this current study data that evaporation is the primary mechanism of tear film thinning.
Advisors/Committee Members: Nichols, Jason.
Subjects: Ophthalmology
Keywords: tear film, dry eye, evaporation, tear film thinning, interferometry, mechanisms of tear film thinning
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21.
Kuchem, Mallory Kuhlmann.
Ciliary muscle, eye shape, and accommodation in adults with anisometropia.
Degree: MS, Vision Science, 2012, Ohio State University
► Purpose: The purpose of this study was to investigate the relationships between…
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▼ Purpose: The purpose of this study was to investigate the relationships between ciliary muscle thickness, refractive error, axial length, and accommodative lag in a sample of anisometropic adults. Methods: The right and left eyes of 30 adult subjects were measured. All subjects possessed a difference of at least one diopter of refractive error between the two eyes. Accommodative lag to a 4.00 D target was measured. Then, cycloplegic measurements of the nasal ciliary muscle thickness (CMT), spherical equivalent refractive error, and axial length were made. Ciliary muscle thickness measurements were made at the maximum ciliary muscle thickness (CMTMAX) and at 1.0 mm (CMT1), 2.0 mm (CMT2), and 3.0 mm (CMT3) posterior to the scleral spur using the Zeiss Visanteâ„¢ Anterior Segment OCT. Simple linear regression and multilevel regression models were used to compare ciliary muscle thickness, refractive error, axial length, and accommodative lag both across and within subjects. Results: Across subjects, CMT was significantly negatively associated with mean refractive error and significantly positively associated with mean axial length when refractive error and axial length were first averaged between the two eyes of each subject. This relationship was most pronounced for CMT2 (p < 0.0001). When CMT2 was controlled for, CMTMAX and CMT1, which represent the presumed radial/circular fibers of the ciliary muscle, are significantly positively associated with mean refractive error (p < 0.0001) and significantly negatively associated with mean axial length (p = 0.0002) across subjects. Within subjects, there was no significant difference in ciliary muscle thickness. Accommodative lag was significantly negatively associated with the thickness of the ciliary muscle, but only at CMT2 (p = 0.02) and CMT3 (p = 0.01). Within subjects, no difference in accommodative lag between the two eyes was observed. Conclusions: Across subjects, this sample of anisometropic subjects behaves in accordance with the literature: thicker ciliary muscles are associated with increased myopic refractive error and axial length. Within subjects, however, this relationship ceases to exist, indicating that an eye can grow longer and more myopic than its fellow eye without resulting in an increase in ciliary muscle thickness. Across subjects, the longer, more myopic eyes tended to have thicker posterior portions of their ciliary muscle (posterior to CMT2) and lesser amounts of accommodative lag, while the shorter, more hyperopic eyes tended to have thicker anterior portions of their ciliary muscle and larger amounts of accommodative lag. This suggests a division in both structure and function at the position of CMT2. Specifically, the portion of the ciliary muscle posterior to CMT2 may be more implicated in sustaining accommodation and reducing lag, while the portion of the ciliary muscle anterior to CMT2 may play a greater role in accommodative workload.
Advisors/Committee Members: Bailey, Melissa.
Subjects: Ophthalmology; Optics
Keywords: Ciliary muscle; eye shape; anisometropia; refractive error; axial length; accommodation
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22.
Landrum, Brian Thomas.
The Effect of Letter Size on the Accommodative Response A Thesis.
Degree: MS, Vision Science, 2009, Ohio State University
► Accommodative response was measured on fifteen subjects as they read successive lines…
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▼ Accommodative response was measured on fifteen subjects as they read successive lines on a standard Bailey-Lovie acuity chart at varying levels of defocus. Letter size had a measurable effect on the accuracy of the accommodative response. At large letter sizes the average accommodative response at a 4 D demand was 2.97 ± 0.36D. At smaller letter sizes the average response was significantly larger at 3.44 ± 0.24D (F3.2,45.3 = 22.4, p<0.0001, repeated measures ANOVA). The first significant increase in accommodative response was noted at a letter size of 9.7 minutes of arc (3.27 ± 0.22D; t14= 5.0, p=0.014). The relationship between logMAR acuity and myopic defocus was linear between 0 and –3D. The results were similar under cycloplegia; myopic and hyperopic defocus had roughly the same effect on visual acuity. Taking into consideration all of these factors; excessive lag during reading might be in the range of 1.75 to 2.25D.
Advisors/Committee Members: Mutti, Donald.
Subjects: Optics
Keywords: Accommodative Lag; Hyperopia; Accommodation; Acuity
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23.
Lehman, Bret M.
Validation of Optical Coherence Tomography-Based Crystalline Lens Thickness Measurements in Children.
Degree: MS, Vision Science, 2009, Ohio State University
► The purpose of this study was to evaluate the validity and repeatability…
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▼ The purpose of this study was to evaluate the validity and repeatability of crystalline lens thickness measurements obtained by anterior segment optical coherence tomography (OCT). Optical coherence tomography utilizes infrared light and partial-coherence interferometry to produce a two-dimensional scan of the internal ocular structures in vivo. Changes in crystalline lens thickness are important to monitor for refractive error development, cataract progression, and anterior chamber alterations. Our goal was to develop an effective method of measuring the thickness of the crystalline lens with the Visante anterior segment OCT, to assess OCT repeatability, and to evaluate OCT validity as compared to A-scan ultrasonography. Forty-seven normal children (mean age ± SD = 11.06 +/- 2.30 years) had their crystalline lens thickness measured with the Visante anterior segment OCT (Carl Zeiss Meditec, Dublin, CA) and with conventional A-scan ultrasonography (Humphrey 820). The subjects’ right corneas were anesthetized, and their right eyes were cyclopleged. Five A-scan ultrasonography measurements and three Visante OCT measurements were made per eye. Thirty-eight subjects had measurements at a second visit where three additional Visante OCT measurements were made. The mean of the differences between the Visante OCT and A-scan ultrasonography was –0.045 mm (p = 0.017), indicating that the average measurement of crystalline lens thickness was thinner with the Visante OCT. The 95% limits of agreement were from –0.29 to 0.20 mm. When validity was assessed using only Visante OCT images that contained the corneal reflex, the mean of the differences was 0.019 mm (p = 0.11) with 95% limits of agreement from –0.091 to 0.13 mm. For the repeatability of the Visante OCT, the mean of the differences between visit one and visit two was –0.008 mm (p = 0.25) with 95% limits of agreement from -0.088 to 0.072 mm. Repeatability improved when reassessed using only images that contained the corneal reflex; the mean of the differences for these images was –0.0001 mm (p = 0.97) with 95% limits of agreement from –0.030 to 0.030 mm. In comparison to A-scan ultrasonography, a statistically significant difference was observed only when images that did not contain the corneal reflex were included in the analysis. When assessing inter-visit repeatability, a statistically significant difference was not found in either case, but the limits of agreement were narrower when repeatability was assessed using only the images containing a corneal reflex. The Visante OCT is a non-contact instrument that is simple to use, and it provides valid crystalline lens thickness measurements with excellent repeatability. Validity and repeatability were optimized when the Visante OCT images contain the corneal reflex.
Advisors/Committee Members: Zadnik, Karla.
Subjects: Optics
Keywords: Anterior segment optical coherence tomography; crystalline lens; validity; repeatability; Visante OCT; A-scan biometry
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24.
Lewis, Helen Ann.
Ciliary Muscle Morphology in School-Age Children.
Degree: MS, Vision Science, 2011, Ohio State University
► Purpose: To investigate the morphology of the ciliary muscle during the act…
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▼ Purpose: To investigate the morphology of the ciliary muscle during the act of accommodation in a population of children. Methods: Thirty children ages 6 to 12 years were enrolled. Measurements were taken on the right eye only. Accommodative response was measured through habitual correction. Height and weight were measured as control variables. Central axial length was measured with the IOLmaster. Four images of the temporal ciliary muscle were taken with the Visante OCT at three different stimulus levels (0D, 4D, 6D) while accommodative response and pupil size were monitored concurrently with the PowerRefractor. Accommodative response monitoring was time- matched to ciliary muscle image capture, and the mean was calculated for five seconds surrounding this time point. Four cycloplegic images of the temporal ciliary muscle were also taken. Results: Increased accommodative response was correlated with increases in the thickness of CMTmax (p=<0.001) and CMT1 (p=lt;0.001), and decreases in the thickness of CMT3 (p=<0.001). Thicker values of CMTmax under cycloplegic conditions were significantly correlated with values of CMTmax (p=<0.001) and CMT1 (p=0.001) while accommodating, and approached significance in modeling CMT3 (p=0.06). Mean axial length was correlated with the amount of thinning at CMT3 with accommodation (p=0.002). Axial length was not significantly correlated with thickness values at CMTmax (p=0.7) or CMT1 (p=0.6). No significant coefficients were found for modeling CMT2. Conclusions: Knowledge of the accommodative response is important when analyzing ciliary muscle thickness in vivo because it is correlated with ciliary muscle thickness at CMTmax, CMT1, and CMT3. Further investigation is necessary to determine if significant factors for modeling CMT2 exist or if there is a “fulcrum” point along the length of the ciliary muscle where the net change with accommodation is always zero.
Advisors/Committee Members: Bailey, Melissa.
Subjects: Health Sciences
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25.
Lewis, Kristen Oblad.
COMPARATIVE LIPIDOMICS OF HYDROGEL CONTACT LENSES IN-VITRO AND IN-VIVO.
Degree: MS, Vision Science, 2009, Ohio State University
► Contact lenses remain a popular option for the correction of ametropia with…
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▼ Contact lenses remain a popular option for the correction of ametropia with an estimated 125 million contact lens wearers throughout the world. Silicone hydrogel lenses, a new contact lens material, allow for more oxygen to reach the ocular surface, the interaction between this hydrophobic material and the hydrophilic layer of the tear film may lead to ocular complications, such as dry eye. Approximately 80% of problems found in contact lens wearers are caused by molecules from the tear film depositing onto the lenses. Contact lens deposition can cause a decrease in visual acuity, contact lens comfort, and contact lens wettability which leads to an increased inflammatory response and thus dry eye symptoms. In 2003, Jones et al. showed that silicone hydrogel lenses deposited less protein but more lipid compared to traditional hydrogel lenses. To further advance the contact lens field research is needed to compare traditional hydrogel lenses and silicone hydrogel lenses to adequately assess the effect of silicone hydrogel lenses on the ocular surface. The range of analytical methods used to research contact lens deposition needs to be narrowed in order to compare results across studies. The purpose of this study is to analyze lipid deposition on different contact lens materials using assay based techniques and mass spectrometry. This three arm project consisted of an in-vitro portion followed by two in-vivo studies. The in-vitro study consisted of a 5 mM fatty acid amide doping solution containing oleamide, stearamide, erucamide, palmitamide, and myristamide. Etafilcon A, senofilcon A, and lotrafilcon B were rocked in the doping solution for one week then analyzed by Micromass LCT. The second arm consisted of five subjects wearing three lenses (etafilcon A, senofilcon A, and lotrafilcon B) for one week of extended wear and analyzed by Micromass LCT. The third arm of the study and second in-vivo study consisted of 14 subjects wearing etafilcon A, senofilcon A, crofilcon A, and lotrafilcon B each for eight hours then analyzed by mass spectrometry using the Micromass Q-TOF II, a cholesterol assay, a total lipid assay and a phospholipid assay. Oleamide was the most abundant fatty acid amide present on all contact lenses for the in-vitro study and one week in-vivo study. No specific molecule was identified and no type of contact lens showed an increased amount of deposition from the one day in-vivo study. The total lipid assay showed that senofilcon A and lotrafilcon B had the highest amount of total lipid. The phospholipid assay indicated that senofilcon A deposited the greatest concentration of phospholipids. Calculations show a large standard deviation for each lens from both assays which indicate individual variation. The cholesterol assay gave no accurate or valuable data. The results indicate that silicone hydrogel lenses are likely to deposit more lipid molecules in comparison to traditional hydrogel lenses. The total lipid assay and phospholipid assay shows the variation of lipid deposition based on an individual’s tear film chemistry. Further analysis is needed to correctly identify the molecules extracted from worn contact lenses.
Advisors/Committee Members: Nichols, Kelly.
Subjects: Ophthalmology
Keywords: silicone hydrogel, lipid deposition, mass spectrometry
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26.
Lin, Yu-Ju.
Validity and Repeatability of Pediatric Surveys for Spectacles and Contact Lenses.
Degree: MS, Vision Science, 2009, Ohio State University
► For the last 20 years, researchers and clinicians have generated more interest…
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▼ For the last 20 years, researchers and clinicians have generated more interest in the patients’ health-related quality of life (HQOL) affected by disease or treatment, after focusing on treatment itself for years. Several vision-related QOL instruments were developed, but no pediatric refractive error-related QOL instrument exists. Since myopia usually develops during childhood, it is important to find out how children feel about vision correction and how glasses or contact lenses influence their life in order to offer better eye care services. Two pediatric surveys, the Pediatric Refractive Error Profile (PREP) and the Spectacle Survey, have been designed to answer these questions. The purpose of this study is to examine the validity and repeatability of the PREP and Spectacle Survey.The PREP for Glasses and Contact Lenses were completed at two separate visits by 30 spectacle wearers and 27 contact lens wearers, respectively. Scale scores of the same survey completed twice were compared by paired t-test, 95% limits of agreement, and intraclass correlation coefficients to test repeatability. The agreement between the parents’ report and PREP scale scores were analyzed to examine concurrent validity. The examiner’s opinion about how much the child likes to wear his or her glasses/ contact lenses was compared to detect whether it is correlated with PREP scale scores. Internal consistency was evaluated by Cronbach’s α and inter-item correlation. The repeatability and validity of the Spectacle Survey were examined the same way as PREP. There was a lack of bias between administrations of the PREP for all scales (Student’s paired t-test, p > 0.005). Among all scales, the Far Vision for glasses and Activities for contact lenses showed the widest 95% limits of agreement and lowest ICC. Comparison of parents’ report and the PREP, revealed poor to moderate agreement, depending on the particular scale. The PREP for Glasses (range: 0.04 to 0.48) showed better agreement with parents’ report than for Contact Lenses (range: 0.03 to 0.44). There was not a statistically significant correlation between examiner’s opinions and the PREP (Kruskal Wallis, p = 0.11 for glasses and 0.82 for contact lenses). The Cronbach’s α indicated the moderate to high internal consistency for all scales which comprised more than two items in PREP (range: 0.51 to 0.79 for glasses and 0.41 to 0.76 for contact lenses). The Spectacle Survey showed better repeatability than the PREP and exhibited adequate agreement with parents report for most of scales (range: 0.04 to 0.66). There was marginally significant correlation between examiner’s opinions and Spectacle Survey scales (Kruskal Wallis, p = 0.04 to 0.66). The Cronbach’s α coefficient showed good internal consistency (range: 0.66 to 0.82). Further improvement of survey design, such as increasing item numbers within scales, should be made especially for the PREP in order to obtain accurate knowledge of children’s satisfaction with glasses or contact lenses, and their quality of life affected by vision correction.
Advisors/Committee Members: Walline, Dr. Jeffrey.
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27.
Lossing, Laura Ashley Eisele.
Changes in Ciliary Muscle Thickness with Accommodation.
Degree: MS, Vision Science, 2011, Ohio State University
► Purpose: To develop a measurement protocol using the Zeiss Visante™ AS-OCT to…
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▼ Purpose: To develop a measurement protocol using the Zeiss Visante™ AS-OCT to asses changes in the shape and size of the ciliary muscle with accommodation and to determine the test-retest repeatability of these measurements. Methods: Twenty-five adults (17 females) ages 22-27 years (mean ± SD = 23.8 ± 1.1 years) were recruited. The ciliary muscle was imaged at two separate visits two weeks apart with the Zeiss Visante Anterior Segment OCT. While subjects viewed targets at two different stimulus levels (1 D and 4 D), the ciliary muscle was imaged six times and accommodation was monitored with the PowerRefractor. Ciliary muscle thickness (CMT) measurements were obtained at four muscle locations; 1 mm (CMT1), 2 mm (CMT2), and 3mm (CMT3) posterior to the scleral spur as well as (CMTMAX) at the point of maximal muscle thickness. The action of the ciliary muscle during accommodation was described by our data in two ways. The „raw change‟ was calculated as the change in ciliary muscle thickness calculated based on the accommodative target (the change in accommodation from distance to the 4D target). The „standardized change‟ was calculated as the ratio as (change in CMT/accommodative response) represented the amount of thickening or thinning that occurred in the ciliary muscle per diopter of accommodation. Finally, the repeatability measurements between visit 1 and visit 2 were analyzed using a Bland-Altman analysis. Results: The mean accommodative response measured with the PowerRefractor at visit 1 was 3.97±0.87D with a range of -1.87 to -4.95D and -3.92±0.82 with a range of -2.79 to -5.39D at visit 2. The change in ciliary muscle thickness per diopter of accommodation was calculated based on both the accommodative stimulus and the measured accommodative response (PowerRefractor) at the four thickness locations. Ciliary muscle thinning from 1D to 4D of accommodation was statistically significant at CMT3. Thickening of the ciliary muscle with accommodation was observed at both CMT1 and CMTMAX while no statistical thickening or thinning was present at CMT2. Bland-Altman repeatability analysis between the two visits was non-significant for every muscle location. The 2D stimulus was not considered in these calculations because the majority of subjects failed to produce any accommodative effort to the 2D target. Conclusion: The combination of the Visante Anterior Segment OCT and the PowerRefractor is a feasible tool for measuring the change in ciliary muscle thickness with accommodation. There was a wide range of accommodative responses during the time of image capture in this study. This indicates is it essential to know the accommodative response at the exact time of image capture for the most accurate calculations of change in ciliary muscle thickness with accommodation.
Advisors/Committee Members: Bailey, Melissa.
Subjects: Medical Imaging; Ophthalmology; Optics
Keywords: Accommodation; Myopia; Presbyopia; Ocular; Visante; Ciliary muscle
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28.
Marks, Amanda R.
Nutrition, Vitamin D and Refractive Error.
Degree: MS, Vision Science, 2010, Ohio State University
► Purpose: Several factors have been found to be candidate risk factors in…
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▼ Purpose: Several factors have been found to be candidate risk factors in myopic development and progression. Outdoor activity, in particular, has been found to be protective in the development of myopia. A possible component of outdoor activity could be vitamin D. We are investigating the effects of activity as well as dietary and circulating levels of vitamin D on myopes and non-myopes. Methods: Thirty-two subjects provided information regarding diet and activity by means of surveys. A smaller number of subjects that met refractive error criteria (n=22) provided 200 μl of blood to analyze circulating vitamin D as well as a 2 ml sample of saliva for SNP analysis of the vitamin D receptor gene. Results: Activity, both indoors and outdoors, were not significantly different for myopes versus non-myopes. Unadjusted levels of circulating vitamin D were not significant as well. Linear regression adjusted for four dietary variables (calcium, food folate, theobromine, and total sugar) and age showed myopes had 3.41 ng/ml less circulating blood vitamin D than non-myopes (p=0.005, R-squared=0.76). Odds ratios from SNP analysis of VDR gene were not significant in increasing the risk of being myopic. Conclusions: Outdoor and indoor activities were not significantly associated with circulating levels of vitamin D. Calcium and theobromine were positively associated while food folate and total sugar were negatively associated with blood vitamin D levels. Blood vitamin D levels were lower in myopes once adjusted for age, and dietary variables. Other intrinsic factors including single nucleotide polymorphisms in the vitamin D receptors were not significant for increasing the risk of being myopic.
Advisors/Committee Members: Mutti, Donald.
Subjects: Nutrition; Ophthalmology
Keywords: refractive error, myopia, nutrition, diet, vitamin D
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29.
McVey, Mary Elizabeth.
The Bifocal Lens Inhibition of Myopia Progression (BLIMP) Study.
Degree: MS, Vision Science, 2010, Ohio State University
► The Bifocal Lens Inhibition of Myopia Progression (BLIMP) Study is a two…
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▼ The Bifocal Lens Inhibition of Myopia Progression (BLIMP) Study is a two year study comparing the progression of myopia in forty children ages eight to eleven fit in bifocal soft contact lenses to age- and gender-matched children fit in spherical soft contact lenses in the Adolescent and Child Health Initiative to Encourage Vision Empowerment (ACHIEVE) Study. Few studies have explored bifocal soft contact lenses for myopia progression inhibition, and no full studies have been published in peer-reviewed publications. This thesis only includes the one year data of twenty eight children, and all data are confidential. Distance center bifocal soft contact lenses are being used in this study. This is to allow accurate focus of light on the fovea for clear vision while providing peripheral retinal myopic blur that animal studies have shown to change eye growth patterns. Refractive quality of life assessment took place before subjects were fit in contacts and at every follow-up visit. Their refractive quality of life improved and was equivalent to that of children fit in spherical soft contact lenses in the ACHIEVE Study. Previous studies have explored lined bifocal spectacles, no-line bifocal spectacle lenses, and bifocal soft contact lenses as myopia progression inhibition methods assuming accommodative error or effort is part of what drives myopia progression. We fit twenty eight pediatric subjects in bifocal soft contact lenses and followed them for a period of one year. We measured refractive and biometric data at baseline and one year. The same data were measured in a historical control group of twenty eight age- and gender-matched spherical soft contact lens wearers. Our data suggest that the children fit in bifocal soft contact lenses had less increase in their myopia over a year than the children who wore single vision spectacles (SVLs). The average (±SD) rate of progression of the spherical equivalent refractive error of the soft bifocal contact lens subjects was -0.39 ± 0.53 D for the right eye and -0.40 ± 0.39 D for the left eye. The rate of progression of the spherical equivalent refractive error of the soft spherical contact lens subjects was -0.60 ± 0.32 D for the right eye and -0.54 ± 0.34 D for the left eye. These progressions were not significantly different (Student’s t-test, p = 0.08 and p = 0.15). The axial length data were not consistent with the refractive error data. The axial length of the soft bifocal contact lens subjects’ eyes increased by 0.18 ± 0.22 mm in the right eye and by 0.11 ± 0.23 mm in the left eye. The axial length of the soft spherical contact lens subjects’ eyes increased by 0.23 ± 0.17 mm in axial elongation of the right eye between soft bifocal and soft spherical contact lens wearers (Student’s t-test, p = 0.329), but the left eyes of the spherical soft contact lens wearers grew significantly more than the left eyes of the bifocal soft contact lens wearers (Student’s t-test, p = 0.004). Our study has not found a significant decrease in progression of myopia in children fit in bifocal soft contact lenses at this sample size.
Advisors/Committee Members: Walline, Jeffrey.
Subjects: Ophthalmology
Keywords: myopia progression; soft contact lenses
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30.
Meadows, Jillian Faith.
Development of the 4-3-2-1 Meibum Expressibility Scale and Omega-3 Fatty Acid Supplementation and Dry Eye.
Degree: MS, Vision Science, 2011, Ohio State University
► OBJECTIVES: Dry eye disease and meibomian gland dysfunction are both prevalent conditions…
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▼ OBJECTIVES: Dry eye disease and meibomian gland dysfunction are both prevalent conditions that lead to alterations of the tear film and consequent ocular surface damage. Despite the increased interest in the assessment of both of these conditions, there still remains a deficit in simple, clinically applicable grading scales for meibomian gland expression and effective therapeutic management options for dry eye disease. Therefore, two distinct studies with overlapping designs were executed to (1) develop a clinical grading scale for the assessment of meibomian gland expressibility and to (2) evaluate the efficacy of omega-3 fatty acid supplementation in a randomized, placebo-controlled, double-masked, pilot study of dry eye disease. METHODS: A meibum expressibility scale was developed using a new standardized meibomian gland expression device, which provides constant pressure along the inferior lid. For the scale development, 30 patients (52.5 ± 12.4 years; 93.33% female) with mild to moderate dry eye were compared to 13 normal, non-dry eye subjects (25.6 ± 4.3 years; 46.1% female). The device was placed 4 glands lateral to the inferior punctum and 1 mm below the inferior lash line and held stable for 15 seconds, such that the glands expressing meibum were then counted. The weighted kappa statistic was used to evaluate the extent of agreement between visits in the normal sample, and a Receiver Operating Characteristic (ROC) curve was created to test the proposed scale. The same 30 dry eye patients were then randomized to either omega-3 fatty acid supplementation or soybean oil (placebo) and followed at 4-week intervals for 8 weeks. Outcome variables were tear osmolarity, OSDI score, SANDE analog values, and artificial tear reliance. RESULTS: For the meibum expressibility scale, the mean number of glands that expressed from the worse lid in the normal group was 3.54 ± 1.61, while 1.53 ± 1.28 glands expressed in the dry eye group. In the dry eye group, one subject showed 5 glands expressing, and 29 had scores of 4 or less. In the normal group, 11 of 13 patients expressed from 3 or more glands. In the omega-3 study, there were no detectable associations with any of the clinical variables in the treatment arm. The placebo group trended toward improvement in osmolarity (worse eye), OSDI (baseline versus 8 weeks), SANDE values (at 4 weeks and 8 weeks), and tear reliance (at 8 weeks). CONCLUSION: A 4-3-2-1 meibomian gland scoring system is proposed, whereby 4+=normal expressibility, 3=mildly reduced expressibility, 2=moderately reduced expressibility, and 1 or 0=severely reduced expressibility. Further validation of the scale is warranted. For the study assessing omega-3 fatty acid supplementation, there was little to no observed therapeutic benefit of omega-3s in this sample of dry eye patients. Further, soybean oil seems to lack the inert qualities of an appropriate placebo in a clinical trial of dry eye disease. Additional studies that incorporate a proper dosage, an adequate placebo, and omega fatty acid dietary consumption in their study designs are necessary to determine the therapeutic value of omega-3s in the management of dry eye disease.
Advisors/Committee Members: Nichols, Kelly.
Subjects: Ophthalmology
Keywords: dry eye, meibomian gland dysfunction, omega-3 fatty acids
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