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1 Role of Accommodation in Clinical Measures of Proximal Vergence

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1 Role of Accommodation in Clinical Measures of Proximal Vergence Role of Accommodation in Clinical Measures of Proximal Vergence Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Rachel Fenton Graduate Program in Vision Science The Ohio State University 2019 Thesis Committee Nicklaus Fogt, O.D., M.S., PhD, Advisor Catherine McDaniel, O.D., M.S. Donald Mutti, O.D., PhD 1 Copyrighted by Rachel Fenton 2019 2 Abstract Proximal vergence is the subtype of vergence that is stimulated by visual cues other than blur and disparity. There are two major clinical methods to assess proximal vergence. In one of these methods, termed the AC/A differencing method, proximal vergence is determined by calculating the difference in vergence change from the far-near AC/A method and the vergence change from the gradient AC/A method (equated for the accommodative demand). In the other method, termed the +2.50D method, the change in vergence posture between distance viewing and near viewing through a +2.50D lens is calculated. In assessing these values, it is typically assumed that response accommodation matched the change in accommodative demand from distance to near, which would be 2.50D for a 40cm near viewing distance. However, individuals often do not alter their accommodation by the amount of the accommodative demand. Therefore, proximal values calculated using accommodative responses might vary from proximal values that are calculated using the accommodative demand. The purpose of the present research is to determine the extent to which response accommodation could influence these methods of assessing proximal vergence, in order to better understand how proximal vergence is measured and therefore to better understand the relationship between proximal vergence and the other vergence subtypes in future studies. Thirteen subjects were recruited, ages 22-37, who underwent a battery of measurements consisting ii of interpupillary distance, visual acuity, stereoacuity, accommodative amplitudes, step vergence ranges, distance heterophoria, and near heterophoria using various refractive lenses. A Grand Seiko WR5100K autorefractor measured accommodation. Accommodative data revealed high accommodative lags in many subjects, which influenced response AC/A ratios and response proximal vergence results. Proximal vergence was then calculated in four distinct ways, two based on stimulus measurements and two taking response accommodation into consideration. Statistical analysis using t- tests showed no statistically significant difference between any of these proximal vergence calculations after using the Bonferonni correction (p>0.0083 for all comparisons). Additionally, no statistically significant relationship between measures of fusional vergence and measures for proximal vergence were found (p>0.05) using linear regression analysis. In conclusion, this study found that all four clinical methods, using stimulus and response measurements, yielded similar values. iii Dedication I would like to dedicate this to my parents, brother, and fiancé for their continued love, support, and encouragement. iv Acknowledgments I would like to thank my thesis advisor for his assistance and feedback throughout this project, as well as those who served on my thesis defense committee for their thoughtful critiques of this research and thesis. I additionally would like to thank all of my loved ones for their encouragement throughout this project. The project described was supported by Award Number Grant UL1TR002733 from the National Center For Advancing Translational Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center For Advancing Translational Sciences or the National Institutes of Health. v Vita Denison University (2010-2014): Bachelor of Arts in Psychology The Ohio State University (2015-present): Seeking O.D. degree The Ohio State University (2016-present): Seeking M.S. degree Publications Matthews, N., Welch, L., Achtman, R., Fenton, R., & FitzGerald, B. (2016). Simultaneity and temporal order judgments exhibit distinct reaction times and training effects. PLoS ONE, 11(1). doi: 10.1371/journal.pone.0145926 Fields of Study Major Field: Vision Science vi Table of Contents Abstract ............................................................................................................................... ii Dedication ........................................................................................................................... iv Acknowledgments ............................................................................................................... v Vita ..................................................................................................................................... vi List of Tables ...................................................................................................................... ix List of Figures ...................................................................................................................... x Chapter 1. Introduction and Literature Review ................................................................... 1 Chapter 2. Methods ........................................................................................................... 13 Participants: ................................................................................................................... 13 Procedure: ...................................................................................................................... 14 Chapter 3. Results .............................................................................................................. 20 General Data Interpretation: .......................................................................................... 20 Stimulus Proximal Values: AC/A Differencing Method and +2.50D Method ............. 21 Proximal Vergence Calculations for Stimulus Values .................................................. 23 Far-Near Differencing Method with Stimulus AC/A ................................................ 23 The +2.50D Method .................................................................................................. 24 Statistical Analysis of Stimulus AC/A Differencing and +2.50D Proximal Vergence ................................................................................................................................... 25 Refractive and Accommodative Measures .................................................................... 26 Response Far-Near AC/A Ratio and Response Gradient AC/A Ratio .......................... 31 Proximal Vergence Calculations for Response Values ................................................. 32 AC/A Differencing Method with Response AC/A .................................................... 32 +2.50D Method Corrected for Remaining Accommodation ..................................... 33 Statistical Comparisons for Proximal Vergence Values ............................................... 35 Statistical Analysis: Vergence Ranges versus Proximal Values ............................... 37 vii Bibliography ...................................................................................................................... 42 viii List of Tables Table 1. The accommodative amplitudes, vergence ranges, and heterophoria values ...... 21 Table 2. Stimulus far-near AC/A values and stimulus gradient AC/A values .................. 23 Table 3. Proximal vergence values using the stimulus AC/A far-near differencing method and the stimulus +2.50D method ....................................................................................... 25 Table 4. Expected and measured (actual) change in accommodation from distance to near ........................................................................................................................................... 28 Table 5. Change in accommodation induced by the +1.00D lens at near, and the accommodation remaining when viewing through the +2.50D lens at near ..................... 31 Table 6. Response far-near AC/A values and response gradient AC/A values ................. 32 Table 7. Response AC/A differencing proximal values and +2.50D (corrected for accommodation) proximal values ...................................................................................... 34 Table 8. Results of paired t-tests for proximal values obtained by the four clinical methods applied in this experiment ................................................................................... 36 ix List of Figures Figure 1. The static accommodative stimulus-response curve ............................................ 5 Figure 2. Distance Modified Thorington card with incandescent lamp ............................ 15 Figure 3. Half-eye trial frame with refractive lenses and Maddox lens ............................ 16 Figure 4. Autorefractor with near Modified Thorington card attached to near point rod . 17 Figure 5. Schematic of the experimental protocol ............................................................. 19 Figure 6. Scatter plot with best fit line between Stimulus AC/A Differencing proximal vergence values and +2.50 Method Uncorrected proximal vergence values .................... 26 Figure 7. Scatter plot with best fit line between Response AC/A Differencing proximal vergence values and +2.50 Method Corrected proximal vergence values ........................ 34 Figure 8.
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