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Contrast Sensitivity and Visual Acuity in Low-Vision Students Thesis Contrast Sensitivity and Visual Acuity in Low-Vision Students Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Steve Murimi Mathenge Njeru, BS Graduate Program in Vision Science The Ohio State University 2020 Thesis Committee Angela M. Brown, PhD, Advisor Bradley E. Dougherty, OD, PhD Deyue Yu, PhD Copyrighted by Steve Murimi Mathenge Njeru 2020 Abstract Purpose: This study primarily compared the test-retest reliability of the Pelli-Robson chart (PR) and Ohio Contrast Cards (OCC) amongst testers. The secondary goal of this study was to examine the impact on contrast sensitivity if the testing distance for the Pelli-Robson chart were to be changed. An additional goal was to evaluate the relationship between visual acuity (VA) and contrast sensitivity (CS) when using letter-based charts and grating cards. Methods: Thirty low-vision students were tested, ranging from 7-20 years old. Each student was tested with both VA and CS tests in randomized order, which included: the Bailey- Lovie chart (BL), Pelli-Robson chart, Teller Acuity Cards (TAC), and Ohio Contrast Cards. Each student repeated both the PR chart and OCC in separate rooms, but neither the BL chart nor TAC was repeated. The PR chart was also tested at closer testing distance, based on the student’s logMAR acuity from the BL chart. For the letter charts, a letter-by-letter scoring method was used. For grating cards, these were both scored as preferential looking tests. Results: The Limits of Agreement for the OCC and PR chart were +/- 0.451 and +/- 0.536, respectively. There was no statistically significant difference between tester or order of testers for the PR chart and OCC. Using the PR chart at a closer distance yielded an improvement in contrast threshold performance when compared to the standard testing distance. Students performed better on grating cards than letter charts, regardless of VA testing or CS testing. Conclusions: The Ohio Contrast Cards are a promising diagnostic tool for evaluating CS on low-vision patients and other patients who cannot be tested using letter-based charts. Clinicians using the Pelli-Robson chart for low-vision patients should consider testing closer than the standard testing distance. iii Dedication This is dedicated to my family, friends, and mentors, who have always supported me in all my endeavors. iv Acknowledgments Ohio State School for the Blind Dr. Gregory R. Hopkins III, OD, MS Faustina O. Opoku, BS v Vita May 2012……………High School Diploma: P.K.Yonge Developmental Research School May 2016……………Bachelor of Science: Biomedical Sciences, University of Central Florida Publications Waddell, J. C., Njeru, S. M., Akhiyat, Y. M., Schachner, B. I., Correa-Roldán, E. V., & Crampton, W. (2019). Reproductive life-history strategies in a species-rich assemblage of Amazonian electric fishes. PloS one, 14(12). Fields of Study Major Field: Vision Science vi Table of Contents Abstract ........................................................................................................................................... iii Dedication ........................................................................................................................................ iv Acknowledgments ............................................................................................................................ v Vita .................................................................................................................................................. vi List of Tables ................................................................................................................................ viii List of Figures .................................................................................................................................. ix Chapter 1. Introduction ..................................................................................................................... 1 Chapter 2. Methods ......................................................................................................................... 14 Chapter 3. Results ........................................................................................................................... 22 Chapter 4. Discussion ..................................................................................................................... 34 Chapter 5. Conclusions ................................................................................................................... 39 References....................................................................................................................................... 40 Appendix A. Consent Form for Ages 18 and Older ....................................................................... 43 Appendix B. Consent Form for Ages 12-17 ................................................................................... 44 Appendix C. Room Checklist for Setup ......................................................................................... 46 Appendix D. Data Collection Sheet................................................................................................ 48 Appendix E. Gift Card Receipt ....................................................................................................... 50 vii List of Tables Table 1 Subject Demographics and Visual Disorders .................................................................... 16 Table 2 Randomized Testing Sequence ......................................................................................... 21 viii List of Figures Figure 1 Bailey-Lovie Chart ............................................................................................................ 3 Figure 2 Teller Acuity Cards ........................................................................................................... 4 Figure 3 Pelli-Robson Chart ............................................................................................................ 5 Figure 4 Lighthouse Letter Contrast Sensitivity Test (Mars chart) ................................................. 6 Figure 5 Arden Grating System ....................................................................................................... 8 Figure 6 Vistech Vision Contrast System ........................................................................................ 9 Figure 7 Functional Acuity Contrast Test ..................................................................................... 10 Figure 8 Melbourne Edge Test ...................................................................................................... 11 Figure 9 Ohio Contrast Cards ........................................................................................................ 12 Figure 10 Testing Materials in Each Testing Room ...................................................................... 20 Figure 11 Bailey-Lovie Chart vs. Pelli-Robson Chart ................................................................... 23 Figure 12 Teller Acuity Cards vs. Ohio Contrast Cards ................................................................ 24 Figure 13 Bailey-Lovie Chart vs. Teller Acuity Cards .................................................................. 25 Figure 14 Pelli-Robson Chart vs. Ohio Contrast Cards ................................................................. 27 Figure 15 Repeatability of Pelli-Robson Chart ............................................................................. 29 a) Tester 1 vs. Tester 2 b) AMB vs. SMN Figure 16 Repeatability of Ohio Contrast Cards ........................................................................... 31 a) Tester 1 vs. Tester 2 b) AMB vs. SMN Figure 17 Pelli-Robson (one meter) vs. Pelli-Robson (closer distance) ......................................... 33 ix Chapter 1. Introduction Purpose Many eye practitioners use visual acuity (VA) to determine the overall visual abilities of their patients. Visual acuity is extensively used in both comprehensive and problem focused eye exams where visual defects from ocular disease (e.g. diabetic retinopathy) or refractive error (e.g. myopia) are suspected. However, VA does not always reveal the full story of a patient’s visual abilities. Other vision tests such as contrast sensitivity (CS) are often used in combination with visual acuity to gain a better understanding on quality of life (Marron & Bailey, 1982). Contrast sensitivity is an individual’s ability to distinguish an object from its background using luminance as a cue. This is often used to help with everyday mobility tasks like navigating through a room or telling the difference between the sidewalk and street (Marron & Bailey, 1982). Many practitioners test both VA and CS on their low-vision patients, but only test VA on their normal-sighted patients. Contrast sensitivity testing used to have a reputation for being too unreliable, too difficult to test, and unrelated to quality of life (Moseley & Hill, 1994). However, past and current research has established standardized methods for testing that are easier for examiners to use, provide more reliable data from patients, and show how changes in contrast sensitivity can affect quality of life. The Pelli-Robson and Snellen letter charts are easy to use on most verbal normal-sighted or low-vision patients. However, for non-verbal, disabled, or developmentally delayed patients, the Pelli-Robson
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