Optometry and Vision Science

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Browsing Optometry and Vision Science by Author "Hovis, Jeffery"

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    Colour Vision Deficiencies in the Digital Age: A Survey of User Experiences with Digital Displays
    (University of Waterloo, 2024-07-09) Mazur, Sandra; Hovis, Jeffery
    Introduction: Approximately 90% of dichromats and 67% of anomalous trichromats experience difficulty performing colour-related tasks daily (Steward & Cole, 1989). As technology becomes more prevalent, examining whether this condition impacts their use of digital displays is increasingly essential. Limited studies analyze the relationship between colour vision deficiencies (CVD) and digital displays. Mashige (2019) found that 63.2% of schoolchildren with CVD reported challenges when “working with computers,” suggesting that this condition may have some effect. Purpose: The purpose of this study is to examine the impact that congenital red-green CVD has on an individual’s interaction with digital displays in different areas of their daily life, such as “school,” “work/volunteering,” “gaming and eSports,” “driving/motorized vehicle,” and “travelling.” Materials and Method: An online survey was administered to people with CVD from Canada and the United States of America (USA). In addition to collecting demographic information and awareness of their CVD, information regarding difficulties carrying out colour-related tasks was collected. Because several software and filter options may improve performance on colour-related tasks, we asked whether they tried any and to rate their effectiveness. Results: A total of 381 individuals with CVD (280 males) completed the survey. Nearly 100% reported some difficulty with one of the tasks in most areas of life, individually, except for travelling (54.1%). For most tasks, there were no significant differences in the rankings based on sex and/or age group. Still, some tasks showed significant differences based on severity, primarily between mild and severe defects. Some examples included “colour-coded diagrams” at school, work/volunteering, and recreation/hobbies; “editing photos or other coloured images” at school, recreation/hobbies, and social media; and “reading coloured letters on various backgrounds” in gaming/eSports, online shopping/banking, and in-person shopping/banking. Nearly 65% of respondents reported making changes or implementing modifications to their displays, but there were 35% who did not. The most popular aid was “trial-and-error adjustments” of the colour and brightness of the display. Of the individuals who tried an aid, approximately 90% reported a modification to be at least a little effective, less than 3% reported at least one aid as ineffective, and only 25% rated the modifications as highly effective. There was no significant difference based on sex, age group, or severity for most modifications, except for passive aids (“coloured filters”) where youth found them more effective than adults. “Desktops/laptops,” “cell phones,” and “tablets” were the displays that people with CVD most frequently encountered difficulty and modified. The displays showed significant association with age group for some areas of life (work/volunteering, recreation/hobbies, gaming & eSports, and online shopping/banking) and modifications. This was probably due to the greater use of displays or differences in content, with youth having more problems with tablets and adults more with cell phones. Conclusion: Most respondents encountered some difficulty with at least one task, indicating that CVD had some effect on their ability to use digital displays. Although most respondents have tried some modifications to their displays, some respondents reported that at least one modification was ineffective and only 25% found an aid to be highly effective. Software developers should focus on making aids more accommodating and customizable to individual preferences.
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    Modeling age-related ocular media changes using the Farnsworth Munsell (FM) 100-Hue Test
    (University of Waterloo, 2021-08-31) Opoku-Yamoah, Victor; Hovis, Jeffery
    Introduction: Evaluation of chromatic discrimination can help diagnose and monitor diseases and disorders of the visual system; however, normal age-related changes can make diagnosing colour discrimination losses challenging. This problem holds especially for the Farnsworth Munsell 100 Hue test (FM100 Hue). Identifying specific contributions of areas of the visual system that influence the FM100 Hue performance could aid in establishing standardized interpretation of test results and help understand the mechanisms contributing to the age-related changes. Purpose: This study aimed to examine the theoretical changes in the FM100 Hue scores produced by age-related changes in the ocular media transmittances. These changes were examined with, and without, a von Kries type chromatic adaptation to determine the role of this adaptation process on age-related changes in hue discrimination. Materials and methods: We calculated the CIECAM02 chromaticity coordinates of the FM100 Hue caps for 32-year-old and 74-year-old as ideal observers. These values were then used to predict the ordering of the FM100 Hue caps. The chromaticity coordinates were based on the spectral distribution of Illuminant D65, the spectral reflectances of the individual caps, and the CIE 1931 2o standard observer colour matching functions. In calculating the values of the old observers, we modified the spectral distributions of the D65 light sources using Pokorny et al.’s and van de Kraats and van Norren’s model of media transmittance to account for the relative change in transmittance from a 32-year-old observer to a 74-year-old observer. We also accounted for the decrease in retinal illumination in the older observers due to pupil miosis and the decrease in ocular media luminous transmittance. The order of the caps was based on the minimum colour differences (ΔE) between nearby caps. The mean and standard deviation of the colour differences for each tray was calculated. The mean colour difference was also determined for the caps in the blue-yellow (BY) and red-green (RG) quadrants. Results: With complete and partial adaptation, the Total Error Score (TES) increased from 8 for the younger observer to12 for both older observer models of media transmittance. The ordering for the caps along the blue-yellow axis was unchanged from the younger observer. Without adaptation, the error score for the older observer model increased further. The increase was primarily for caps along the red-green axis for van de Kraats and van Norren’s model, whereas the increase for Pokorny et al.’s model was along both the red-green and blue-yellow axis. The mean colour differences across trays for the young observer model were marginally larger than the old observer models for complete and partial adaptation. When the caps were grouped in the RG and BY quadrants, the mean differences for the older observers were still lower than the young observer. Differences between the BY and RG error scores were also larger for the older observers. Without adaptation, the mean colour differences for the older observer models were uniformly lower than with complete or partial adaptation. Conclusion: The predicted effect of age-related changes in media transmittances on the ordering of the FM100 Hue test showed an increase in the TES, as expected. The increase, however, was primarily due to an increase in the RG partial error score, which disagrees with the psychophysical data showing a larger increase in the BY error score. This discrepancy suggests that age-related neural changes are also occurring, which is consistent with conclusions from other psychophysical studies. The two different models for age-related media changes produced similar changes in the FM100 error scores. Chromatic adaptation may compensate for age-related media changes.
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    Visual Functions in Parkinson’s Disease
    (University of Waterloo, 2018-06-19) Alhassan, Mosaad; Hovis, Jeffery
    Background: Freezing of gait (FOG) is considered to be a motor disorder symptom that affects some Parkinson Disease (PD) patients; however, it is hypothesized that sensory systems may also be involved in FOG. Purpose: The purpose of this thesis is to measure different 2-dimensional (2-D) and 3-dimensional (3-D) clinical visual functions in FOG and non-FOG PD patients. The ability to maintain adequate alignment of the two eyes was assessed by measuring fixation disparity curve. The other objective of this thesis was to look at integrity of autonomic nervous system (ANS) and two non-motor functions mediated by the cholinergic system in FOG and non-FOG PD patients. FOG PD patients may have greater impairment of one, or more, of these functions. Methods: The 2-D visual function measurements included high and low contrast visual acuities using Early Treatment Diabetic Retinopathy Study charts, low spatial frequency contrast sensitivity using Pelli-Robson chart, horizontal and vertical Vernier acuity using The Freiburg Visual Acuity Test. These tests were conducted under photopic, and then under mesopic conditions. The 3-D visual function measurements included local (contour) and global (random dot) stereopsis at near. Local stereoacuity was measured using Circles and MKH-Haase Line tests. Global stereoacuity was measured using the MKH-Haase Steps, TNO, Randot 3, and Butterfly tests. Fixation disparity curves were measured using the Saladin Near Point Card. Constriction and dilation pupil light reflexes (PLRs) were measured by using a handheld monocular pupillometer to evaluate the integrity of ANS. The inspection time (IT) was determined by a simple length discrimination task to evaluate the integrity of the cholinergic system. Twenty-two FOG PD patients, 25 non-FOG PD patients, and 25 aged matched healthy controls (HC) completed all of the measurements in this project. Results: FOG group had worse 2-D visual resolution results than other two groups especially under the mesopic condition. FOG group also had worse stereopsis than the other two groups. An impairment in global stereopsis was more common than local stereopsis in both PD patient groups. The reduction in stereopsis among PD patients was not associated with the fixation disparity. Both PD patient groups showed significant differences from healthy controls in most of PLR constriction parameters. FOG PD patients showed larger deficits than non-FOG PD patients in some of the constriction parameters. Both groups of PD patients had longer dilation latencies than healthy controls. FOG PD patients had slower IT scores than healthy controls. IT scores for the non-FOG PD patients fell in between the FOG and HC results. Conclusions: FOG patients have a greater impairment in both 2-D and 3-D visual functions. Whether these impairments are contributing to the FOG or just associated with FOG is uncertain. FOG patients also had larger impairments in non-dopaminergic mediated functions such as PLRs and IT, which suggests that FOG patients have greater impairment in two functions that involve cholinergic neurotransmitters.