Investigation on light-induced retinal damage in retinitis pigmentosa

Abstract

Purpose : Light-induced retinal damage was observed in animal models of retinitis pigmentosa (RP). However, there is scarce clinical evidence to support the presence of the phenomenon. We hypothesized that if light-induced retinal damage actually exists, photoreceptors under retinal vessels and protected from light exposure may show preserved thickness. We tested the hypothesis using optical coherence tomography (OCT).

Methods : We retrospectively reviewed consecutive patients with clinical diagnosis of RP who underwent vertical OCT scans thorough the fovea. Patients with poor OCT image quality and presence of cystoid macular edema were excluded. We manually measured the outer nuclear layer (ONL) thickness under retinal vessels with diameter 50 μm to 100 μm. As a control, we measured adjacent ONL thickness 100 μm superior and inferior from the center of the vessel. We performed the same measurements in eyes of age-matched healthy controls. We calculated ratio of ONL thickness under the vessel/the average of adjacent ONL thickness and defined this ratio as ONL preservation ratio.

Results : Forty-eight eyes of 34 RP patients and 40 eyes of 26 healthy individuals were included. The mean age of the patients and healthy controls were 57.6 ± 12.2 and 54.2 ± 14.7 years, respectively. The mean ONL thickness under vessels and adjacent area was 38.3 ± 12.6 μm and 37.5 ± 12.7 μm in the patients, and 46.9 ± 9.7 μm and 47.9 ± 9.1 μm in healthy controls. In both groups, ONL thickness under vessels was not significantly different from adjacent ONL thickness (p = 0.78 and 0.62, respectively). Meanwhile ONL preservation ratio in the patients and healthy controls were 1.024 and 0.976, respectively, and there was a significant difference (p < 0.01).

Conclusions : Our findings suggest that light-induced damage exists in RP patients and photoreceptors under the vessel are protected from the light. At the same time, non-significant difference of exact measurement under vessels and adjacent area indicates that the effect is clinically minimal.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.