Browsing by Author "Richdale, Kathryn L."
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Item Anterior Segment Changes in Prediabetes and Diabetes(2022-05-12) Wang, Rachel; Harrison, Wendy W.; Redfern, Rachel; Richdale, Kathryn L.Purpose: It is well known there are many changes in the cornea due to type 2 diabetes mellitus (T2DM). These include decreased corneal nerve fiber density and delayed corneal wound healing. There is some evidence that these changes may start in prediabetes. This thesis aims to determine how the cornea is altered in prediabetes and early T2DM by specifically evaluating corneal nerve fiber density, corneal hysteresis, and central and peripheral epithelial differences between these groups. Methods: Seventy subjects (aged 30–70 years) were recruited. Blood samples and body metrics were taken. Subjects were grouped as: healthy controls (hemoglobin A1c [HbA1c] <5.7%, n=22), prediabetes (5.7-6.4%, n=26), and T2DM (>6.4% or physician diagnosis, n=22). Central corneal subbasal nerve plexus was imaged using in vivo confocal microscopy (Heidelberg confocal microscope). Corneal nerve fiber density was measured. The corneal epithelium thickness and total central corneal thickness was measured centrally and peripherally (8 mm out; Avanti Ocular Coherence Tomographer). Corneal hysteresis values were acquired (Ocular Response Analyzer). Ocular surface symptoms were quantitated using the Ocular Surface Disease Index (OSDI) survey. Appropriate statistics were used for each analysis. Results: Central corneal nerve fiber density was significantly lower in type 2 diabetes compared to prediabetes (p=0.045) and healthy controls (p=0.001). No differences were found in other corneal nerve fiber measures between groups. There was a significant association between HbA1c and corneal nerve fiber density (rho=-0.45, p=0.001) and body mass index (BMI; rho=-0.30, p=0.04). There was an increase in corneal hysteresis with HbA1c (p=0.02, R2=0.14). Corneal nerve fiber density and corneal epithelium thickness levels were not related (p=0.30). Only in the control subjects and those with prediabetes there was thinning of the peripheral epithelium with HbA1c (p=0.043), but not in T2DM. OSDI scores were correlated with HbA1c but not with structural health metrics in the cornea (p<0.03). Conclusion: There are changes that occur in the cornea secondary to T2DM and prediabetes, such as corneal nerve fiber density, hysteresis values, and peripheral corneal epithelial thickness. These findings could be applied to the clinical setting to improve care in patients with prediabetes and T2DM.Item Comparison of Toric Orthokeratology and Soft Toric Multifocal Contact Lenses in Managing the Astigmatic Myope(2022-05-11) Tomiyama, Erin S.; Richdale, Kathryn L.; Berntsen, David A.; Marsack, Jason D.; Zadnik, KarlaPurpose: Myopia management is an important intervention to reduce the risk of vision threatening ocular disease. Contact lens treatments for patients with astigmatism include toric orthokeratology (TOK) and soft toric multifocal (STM) lenses. The purpose of this study was to quantify visual performance and the potential for myopia management efficacy with TOK and STM in moderate to high astigmatic patients. Methods: Thirty adults, age 18-39 years, with myopia (plano to -5.00 D) and refractive astigmatism (-1.25 to -3.50 D) were recruited to complete this five-visit crossover study. Subjects wore both TOK and STM lenses in random order for 10±2 days each. After lens wear, visual performance and acceptance was measured with logMAR visual acuity and patient-reported outcome surveys. Peripheral refraction and wavefront aberrometry were measured to determine the lens’ potential impact for myopia management. Results: Adults, who are critical users, preferred STM for cost when forced to choose between the two corrections. Compared to baseline, TOK induced a myopic shift in defocus (M) at all retinal locations except 20 degrees nasal (all p<0.03), but STM only induced a myopic shift at 20 degrees temporal (p<0.03). TOK resulted in more myopic defocus than STM at all locations (all p<0.05) except 20 degrees nasal and temporal in the left eye. Higher-order root mean square wavefront error (5 mm pupil diameter) was significantly increased with TOK (0.64±0.22 µm) and STM (0.48±0.11 µm) from baseline (0.24±0.08 µm, both p < 0.001), and TOK was elevated compared to STM (p = 0.026). Conclusion: TOK induced greater peripheral myopic defocus and higher-order aberrations, which may indicate improved efficacy for myopia management. Adult astigmats preferred the vision with TOK over STM.Item Continuous Objective Assessment of Near Work, Light Exposure, and Activity(2020-05) Williams, Rachel; Ostrin, Lisa A.; Richdale, Kathryn L.; Ritchey, Eric R.Purpose: Myopia, or nearsightedness, is an epidemic, with up to 90% of the population in urbanized countries affected. Myopia brings with it potentially blinding complications and significant socio-economic burden. Light exposure and near work are known risk factors for myopia. However, evidence regarding the role of near work in myopia is conflicting. Current technology allows for objective measurements of light exposure; however, quantification of near work is assessed via questionnaires, which are subject to poor recall, response, and parent biases. The purpose of this study was to introduce the RangeLife, a novel, custom device developed for continuous, objective measurement of near work. Further, the objective near work output was compared to traditional visual activity questionnaires and activity logs. Methods: We developed the RangeLife, a device for continuous, objective measurement of working distance. Four devices were built, calibrated, and validated. Then, adult subjects wore the device on weekdays and weekend days, while simultaneously wearing an actigraph device for objective measurements of light exposure and activity. Subjects maintained an activity log and answered a visual activity questionnaire. RangeLife data were downloaded and binned into 0.10 m intervals. Objective diopter hours (dh), a weighted measure of near work, were calculated and compared with subjective diopter hours obtained from the questionnaire. Results: Diopter hours for all subjects were significantly higher on weekdays (14.73 ± 4.67 dh) compared to weekends (11.90 ± 4.84 dh, p = 0.05). 94 ± 1.85% of near and intermediate viewing distances were recorded when the subjects were exposed to mesopic and indoor photopic light levels (<1000 lux), and 80.03 ± 2.11% during periods of sedentary physical activity (<320 counts per minute). Subjective reports of time viewing near and intermediate distances significantly overestimated objective measures (p = 0.002). Conclusions: The RangeLife was shown to provide reliable measures of viewing distance, and can be further utilized to understand potential influences of viewing behaviors on refractive error.Item Environmental and Behavioral Factors in Childhood Myopia(2021-08) Bhandari, Khob R; Ostrin, Lisa A.; Richdale, Kathryn L.; Stevenson, Scott B.; Harb, Elise N.Purpose: Near work and light exposure are known risk factors for myopia. This dissertation validates the Clouclip, a rangefinding device, to assess its utility in measuring viewing distance and ambient illumination, and to use it along with an actigraph device and questionnaire to measure environmental and behavioral risk factors for myopia in four different studies. Methods: Study 1 validated the Clouclip for measuring distance and ambient light, and measured viewing behaviors during four near tasks in adults. Study 2 measured viewing behaviors in children during similar tasks as in study 1. Study 3 utilized the Clouclip and Actiwatch in participant’s habitual environment over a one week measurement period in adults. Study 4 used the Clouclip, Actiwatch, and a questionnaire to comprehensively quantify visual behaviors over one week in myopic and non-myopic schoolchildren. Results: Study 1) Clouclip measured distance and ambient light levels were comparable to actual values, and viewing distance in adults differed by type of near task but not by refraction. Study 2) Viewing distance and posture differed in children by type of near task 3) Clouclip- and Actiwatch-measured illumination were correlated, while questionnaire overestimated compared to objective sensors. Study 4) Objective measures showed that myopic children spent a greater amount of time on near + intermediate viewing and less time outdoors compared to non-myopic children. Questionnaire-derived electronic device use was 12.0 ± 0.7 hrs per day with no differences between refractive error groups. Conclusion: Wearable objective sensors allowed precise quantification of behavioral components related to myopia. Findings demonstrate that several factors differ in the visual environment between myopic and non-myopic children.Item Functional Retinal Outcomes and Association with Health Metrics in Patients with Prediabetes and Type 2 Diabetes(2021-05) Karson, Nicole; Harrison, Wendy W.; Frishman, Laura J.; Richdale, Kathryn L.Purpose: Clinical diagnosis of diabetic retinopathy centers around irreversible, damaging vascular changes in the retina. While previous studies have evaluated the neuronal changes that occur in type 2 diabetes (T2DM) before vasculopathy develops, they have not studied glucose dysregulation in prediabetes (preDM) as defined by HbA1c. We aimed to determine if functional metrics are altered in individuals with preDM and T2DM as well as if measures of retinal function in preDM and T2DM are associated with health markers such as anthropometric measures, blood pressure and cholesterol levels. Methods: The study was carried out in two parts. Subjects were classified by HbA1c measures at the time of testing into control (HbA1c ≤5.6%), prediabetes (5.7-6.4%) and type 2 diabetes groups (previously physician diagnosed or with untreated HbA1c ≥6.5%). In experiment 1, we administered the L’Anthony D-15 color vision test, MARS contrast sensitivity test and recorded mfERG for the right eye and then examined the differences between groups (n = 43 subjects). In experiment 2, we included circumference measures, body fat percentage, blood pressure, and cholesterol levels (n = 34 subjects). Results: Color vision confusion scores (CVCSs) were significantly different between the three groups (p=0.009) and of all the factors evaluated, had the strongest association with glucose deregulation. There was an association between higher CVCS and higher HbA1c values across groups as well as specifically within the preDM group when controlling for age (R2=0.29, p=0.01 and R2=0.39, p=0.02 respectively). Also, hip and waist circumference were associated with HbA1c (R2= 0.21, p=0.006 and r2= 0.14, p=0.03 respectively). In a multivariate regression, waist circumference could be used in conjunction with color test results to improve our associative model of HbA1c. Conclusions: Patients with preDM have functional changes, especially those of color vision, that can be measured in the retina before the diagnosis of diabetes. In addition, tests such as waist circumference and color vision are associated with HbA1c values in patients with preDM and T2DM. These changes could serve as biomarkers that could aid in earlier diagnosis of diabetic eye disease. Further studies are needed to see when these metrics change.Item Patient and Parent Perceptions of Myopia Modalities(2022-05) Lattery, Lauren Jayne; Richdale, Kathryn L.; Ritchey, Eric R.; Bullimore, Mark A.Background: Previous studies have reported quality of life (QoL) with soft contact lenses (SCL), orthokeratology (OK), or glasses (GL) in adults and children, but have not compared QoL across all three modalities nor compared adults to children. Studies have compared parent/child QoL responses for visually impaired children, but not in normally sighted children. The aim of this study was to compare QoL of myopic adults and children in GL, SCL, and OK lenses as well as parent/child responses. Methods: Forty-eight adults (aged 18 - 26 years), 49 children (aged 9 - 17 years) and the children’s parents completed Pediatric Refractive Error Profile 2 (PREP2), a validated questionnaire with 7 subscales (symptoms, vision, activities, appearance, peer perception, handling, and overall). Adults and children had to have worn their correction for at least three years. Parents were asked to answer how they thought their child would answer. Scores were compared between age groups, correction groups, and between children and their parents using non-parametric ANOVA, Mann-Whitney U and Wilcoxon Signed Rank tests, as appropriate. Post-hoc pairwise comparisons between correction groups were conducted with Bonferroni adjustment. Results: Average age of adults was 21.9 ± 2.4 and children was 14.1 ± 2.2 years and duration of correction use was 8.2 ± 3.3 for adults and 5.0 ± 2.2 years for children (both p < 0.01). Adult OK wearers were more satisfied with vision (p = 0.04), activities (p < 0.001) and overall (p = 0.03) compared to GL wearers. Children OK wearers reported higher scores for activities than SCL (p = 0.048) and GL wearers (p < 0.001). Parents of contact lens wearers reported higher perceived in activities (OK p < 0.001; SCL p = 0.02), handling (OK p = 0.02; SCL p < 0.001), appearance (SCL p = 0.001), and overall (OK p = 0.001; SCL p < 0.001) subscales than parents of child GL wearers. Conclusion: Activity driven children and adults should consider being fit in OK. Parents’ perceptions did not align with their children’s perceptions of their correction.Item The Effects of Center-Near and Center-Distance Multifocal Contact Lenses on Peripheral Defocus and Visual Acuity(2020-05) Hair, Lea; Berntsen, David A.; Richdale, Kathryn L.; Ritchey, Eric R.Purpose: Multifocal soft contact lenses (MFCLs) are being used for myopia control. This project compares four commercially-available MFCLs (one center-near design and three center-distance designs) to determine their effect on high-contrast and low-contrast logMAR visual acuity (HCVA/LCVA) and changes in retinal defocus along the horizontal meridian of myopic eyes. Methods: Two cohorts of twenty-five non-presbyopic myopic adults (-0.50 to -6.00 D spherical equivalent (SE) myopia and < 1.00 D cylinder) were enrolled. Cohort 1 was fitted with Proclear D and Biofinity D MFCL (center-distance, +2.50D add) and cohort 2 with NaturalVue MFCL (center-distance) and Clariti 1-Day MFCL (center-near, high add), in random order. Visual acuity was optimized with spherical over-refraction. HCVA and LCVA were obtained with each lens and with SE spectacle correction. Cycloplegic autorefraction was performed with each lens and without along the line of sight and at nasal and temporal retinal locations. Data were analyzed with repeated-measures ANOVAs and post-hoc t-tests, when indicated. Results: Compared to SE spectacle correction, Clariti 1-Day MFCL reduced HCVA (1.5 lines) and LCVA (2 lines), and NaturalVue MFCL reduced LCVA (1 line; all P < .05) with no other reductions with the other MFCLs tested. Changes in defocus at each retinal location differed between MFCL designs (lens x location; both P < .0001). The Clariti 1-Day MFCL caused hyperopic changes at multiple peripheral locations (all P < .05). The NaturalVue MFCL caused myopic changes centrally and hyperopic changes at 40° nasal and 30° temporal (all P < .05). The Proclear D and Biofinity D MFCLs caused myopic changes at multiple peripheral locations (all P < .05). Conclusion: The center-near Clariti 1-Day MFCL significantly reduced both HCVA and LCVA and caused hyperopic changes in defocus at multiple peripheral locations, limiting its potential use for myopia control. The center-distance MFCLs did not affect HCVA, but some designs reduced LCVA. Both the Biofinity D and Proclear D caused myopic changes in retinal defocus. The NaturalVue MFCL caused myopic defocus changes centrally but hyperopic changes in the far periphery. Whether differences in center-distance defocus profiles influence the ability to slow myopia progression needs further investigation.Item The Role of Corneal Astigmatism When Fitting Orthokeratology Contact Lenses(2019-08) Tomiyama, Erin S.; Richdale, Kathryn L.; Marsack, Jason D.; Berntsen, David A.Purpose: About one-third of children aged 5-17 years old have astigmatism. Children with increasing astigmatism can also have an accompanying increase in myopia via axial elongation. All of the randomized clinical trials to date have excluded patients with more than 1.50 D of astigmatism and there are limited data on the success of orthokeratology in patients with moderate to high astigmatism. The purpose of this thesis was to assess the fit of sphere and toric lenses and quantify the amount of corneal astigmatism corrected, and to determine the effect of peripheral elevation and central corneal astigmatism on toric orthokeratology fitting. Methods: Two different studies were performed. The first was a retrospective analysis on 32 eyes of 16 subjects, half fitted with sphere and half with toric orthokeratology lenses. The post-treatment data after 1-3 months of successful nightly wear were compared to pre-treatment data to analyze the change in corneal astigmatism. The second study was a prospective analysis of the Pentacam tomography of 25 moderate refractive myopic astigmats (1.25 to 3.50 DC), ages 19 to 38 years. A subset of 20 subjects were fitted with Paragon Dual Axis Corneal Refractive Therapy (CRT) lenses that were worn for 10 2 days. Results: Three methods of analysis showed that the decrease in corneal astigmatism for the spherical lens group was 0.10 - 0.22 D, which was approximately 22 - 31% correction, and the toric group was 0.29 - 0.57 D, which was 20 - 36% correction (all p < 0.006). There was a strong correlation between central corneal astigmatism and corneal elevation at the 4, 6, and 8 mm chords (r = 0.979, r = 0.961, r = 0.927, respectively; all p < 0.001). After Dual Axis lens wear, the average decentration of the treatment zone from the pupil center was 0.29 ± 0.23 mm temporal and 0.13 ± 0.26 mm inferior. Conclusion: Toric orthokeratology lenses correct slightly more corneal astigmatism than spherical lenses. Central corneal astigmatism was highly correlated to peripheral elevation and may be a more expedient measure for clinical use when fitting toric orthokeratology lenses. The amount of treatment zone decentration with toric lenses was minimal which may lead to better visual performance.Item Visual Interaction of Zernike Aberration Terms from 2nd to 5th Radial Orders with Vertical Coma(2020-08) Hu, Chuan; Marsack, Jason D.; Richdale, Kathryn L.; Berntsen, David A.Purpose: Eyes with keratoconus suffer from an increased level of higher-order aberrations and decreased visual performance, even when corrected by conventional rigid contact lenses. This study aimed to characterize the visual interactions between the dominant residual aberration seen in this population (positive vertical coma: C7) and 2nd to 5th radial order Zernike aberration terms. Methods: The experiment proceeded in two parts. In part 1, individual Zernike aberration terms from the 2nd to 5th radial orders were combined in 0.05 μm steps from -2.00 to +2.00 μm with +1.00 μm of C7. The resulting combinations were used to calculate the visual Strehl ratio (VSX), which was used as a surrogate for the relative beneficial/deleterious impact of the combined condition, compared to C7 alone. For conditions where an interaction was predicted to provide the largest improvement (C6 and C17), high-contrast logMAR acuity charts were constructed to simulate the manner in which the combined condition defines the retinal image of the blurred chart. These charts were then read by three well-corrected, typically-sighted individuals through a 3.0-mm artificial pupil. In part 2, the interactions that were predicted to have a deleterious (rather than beneficial) visual interaction with C7 were characterized in greater detail. Results: In part 1, all aberration-containing conditions led to a reduction in visual image quality compared to the aberration-free condition. Levels of C6, C10, C15, C16, and C17 were identified that resulted in higher visual image quality than was observed with +1.00 μm of C7 alone. The acuities of subjects reading convolved charts had a strong correlation with the predicted performance from simulation (C6: r2 = 0.80, and C17: r2 = 0.76). In part 2, all combinations with C4, C5, C11, C12, C13, C18, and C19 were predicted to have worse logVSX than C7 alone. Conclusion: While most interactions reduced visual image quality, limited combinations provided a clinically relevant beneficial effect in the presence of C7. Future work will examine whether these effects persist as the aberration structure of the eye is made increasingly complex, up to the point it mimics an individual with keratoconus.