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Alex Gonzalez, Mariela Aguilar, Cornelis Rowaan, Potyra R. Rosa, Victoria Graham, Byron L Lam, Barry E. Hurwitz, Joseph Carroll, Matthew Feinsod, Jean-Marie A Parel; OPA photosensitivity assessment and algorithm comparison in patients with achromatopsia. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4276.
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The ocular photosensitivity analyzer (OPA, Fig 1, Aguilar et al. BOE 2018,9(11):5583-5596) is an automated instrument to quantify the visual photosensitivity threshold (VPT). The current study assesses visual photosensitivity in patients with achromatopsia using the OPA and compares the VPT results using different algorithms. Given achromatopsia is the target of gene therapy trials, photosensitivity may be a plausible outcome measure in achromatopsia patients who are often disabled by photosensitivity.
The OPA’s first-generation software, (GEN1) implements a stimuli adjustment algorithm incorporating a single unequal staircase, using an episodic stimulus, with reliability catch trials. The (GEN2) stimuli adjustment algorithm utilizes a randomized dual staircase, with pre-test VPT measure as a start point, and episodic stimuli adjustment using a successive approximation procedure. Lastly, the (RAMP) is repeated threshold assessment of five measures, using a continuous ramping light stimulus. Tests were conducted on 8 males with achromatopsia, aged 13 to 25 years. Each stimuli adjustment algorithm was assessed twice, binocularly, in random order, separated by a ten-minute rest period. Lighting in the exam room was adjusted to 4 lux. In all software versions, test instructions were delivered by a computer synthesized audio voice. Participants signal their discomfort (yes/no) via push-button. For GEN1 and GEN2, VPT is calculated as the mean of 10 response reversals, in the (RAMP), VPT is the mean of 5 repeated measures.
Measured VPT (in log(lux) units) across algorithms was analyzed using a repeated measures ANOVA, with means (± SD) of 0.71 ± 0.24 (GEN1), 1.02 ± 0.39(GEN2), and 1.25 ± 0.48 (RAMP). Pairwise comparison showed significant difference between GEN1 and GEN2 (p=0.006) and GEN1 & RAMP (p=0.007). Difference between GEN2 and RAMP was approaching significance (p=0.059). No significant difference (p=0.295), between TESTS 1 & 2 (1.02 ± 0.15 and 0.973 ± 0.11 log(lux) and no significant interactions between retests and algorithms (p=0.303). One subject’s data was not included due to missing timepoints.
In patients with achromatopsia, the underlying stimuli adjustment algorithm and stimuli style (ramp vs episodic) can lead to differences in the VPT measured (Fig 2). Our findings may have implications in the use of the OPA as an outcome measure in achromatopsia clinical trials.
This is a 2020 ARVO Annual Meeting abstract.
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