Quantifying Visual Photosensitivity in Healthy and Achromatopsia Subjects

Abstract

Purpose : Achromatopsia (rod monochromatism), is genetic disorder that affects 1 in 30,000 people and is characterized by decreased vision, discomfort when exposed to light, and inability to differentiate color. The purpose of this study was to quantify visual photosensitivity in healthy and achromatopsia subjects using a combination of psychophysical methods and a self-reported questionnaire.

Methods : Under an IRB approved protocol, 43 healthy subjects (28 females and 15 males, age = 33.3 ± 13.5 y/o, range: 9 to 59 y/o) and 31 subjects with genetically verified CNGA3 or CNGB3 achromatopsia (14 females and 17 males, age = 19.9 ± 12.0 y/o, range: 6 – 57 y/o) underwent visual photosensitivity testing using the Ocular Photosensitivity Analyzer (OPA) (Aguilar et al. BOE 2018, 9(11):5583-5596). The OPA generates light stimuli of varying intensities utilizing unequal ascending and descending steps while instructing the subject to press a button to indicate whether the light stimulus is “uncomfortable”. The visual photosensitivity threshold (VPT) is yielded from the mean of 10 response reversals. Prior to OPA testing, subjects were administered the Visual Light Sensitivity Questionnaire-8 (VLSQ-8) (Verriotto et al. TVST 2017, 6(4):18), a validated self-reported questionnaire that assesses the presence and severity of visual photosensitivity symptoms. The VPT and the VLSQ-8 scores of the healthy and achromatopsia subjects will be compared.

Results : The mean measured VPT in healthy and achromatopsia subjects were 2.4 ± 0.9 log lux and 0.7 ± 0.5 log lux, respectively. A two-sample t-test was performed and showed a statistically significant difference (p < 0.0001) in the VPT. The healthy subjects had a higher VPT and lower scores on the VLSQ-8 as opposed to the achromatopsia subjects which had a lower VPT and higher scores on the VLSQ-8.

Conclusions : Visual photosensitivity was assessed using a combination of psychophysical methods (VPT) and a self-reported questionnaire (VLSQ-8). Our findings demonstrate a significant difference between the subject groups in both VPT and VLSQ-8 scores. Ongoing studies are being performed to quantify visual photosensitivity using the VPT and the VLSQ-8 to establish a baseline, examine disease progression, and evaluate the efficacy of emerging treatments as a clinical outcome measure.

This is a 2020 ARVO Annual Meeting abstract.

 

Figure 1. VPT of the healthy and achromatopsia subjects (± Standard Error).