New Visual Electrodiagnostic and Psychophysical Techniques to Enhance Occupational Performance and Clinical Diagnosis

Date of Degree

5-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Vision Science

Advisor

Jeffrey C. Rabin

Advisor

Brian K. Foutch

Advisor

Christopher M. Putnam

Advisor

Patricia C. Sanchez-Diaz

Advisor

Adam M. Preston

Abstract

Color vision deficiency (CVD) is not uncommon and affects 8% of males and 0.5% of females. Individuals affected with CVD take more time to discriminate colors and make more errors than individuals with normal color vision. This is especially true in cue-limited environments. These characteristics can lead to problematic situations as many daily activities include color coding to refine important and timely choices that arise in all manner of occupational fields including aviation, transportation, medical, and culinary, among others. Mistakes in many of these careers can be costly. Recent research has been released on the effects of color-correcting lenses to enhance CVD performance as well as isolate and exploit color-specific pathways to better detect eye disease. Considering these newer discoveries, this dissertation research focused on utilizing different measures of color vision testing to understand human color vision processing in a more detailed way, employ color perception as a diagnostic tool, and investigate whether color vision is a domain that demonstrates features of neuroadaptation and plasticity. The first study assessed the full-field threshold of the human intrinsically photosensitive retinal ganglion cell (ipRGC) complement. The ipRGC signal was isolated from all other photoreceptors by using selective chromatic adaptation and an S-Cone blocking filter and included monocular and binocular measures. The results provided normative data for a full-field ipRGC threshold applicable to clinical and occupational functions involving the ipRGC pathway. Moreover, results showed a binocular summation effect comparable to classic studies indicating two eyes are better than one suggesting a more conventional ipRGC input to visual perception than previously assumed. The second study determined the normative values of a newly developed cone-specific Parafoveal Sensitivity Test (PFST). The test requires subjects to compare their central chromatic sensitivity to parafoveal sensitivity. The results showed a high degree of threshold agreement across all channels in normal eyes. In the third study, I used the PFST in a population of long-term Hydroxychloroquine (HCQ) users without clearly manifest retinal toxicity. A large degree of within-subject variability was noted. This study also evaluated whether PFST scores were predictive of scoring on current recommended tests that monitor for toxic retinal effects (mfERG, HVF 10-2) or OCT thickness. Although no significant correlations were discovered HCQ users tested worse than normal subjects in each of the cone-specific and luminance channels, highlighting the promise of the PFST in disease populations for early diagnosis and monitoring. The last study was a double-blind, randomized, crossover clinical trial that assessed the efficacy of color-correcting lenses (CCLs) in hereditary CVD subjects. A wide range of threshold and suprathreshold outcome measures were utilized. Cone-specific threshold and suprathreshold tests showed immediate improved performance on day 1 and day 7 with CCLs. There were some improvements without CCLs on day 7 suggesting a perceptual learning or neuroadaptive effect. The short intervention period coupled with non-optimal transmission profile of the prototype CCL used in this study indicates the need for additional research particularly because of promising initial results with the most recent CCL.

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