Abstract
Purpose :
We previously measured photoreceptor-specific perifoveal temporal contrast sensitivities in patients with inherited retinal diseases (IRD) using the silent-substitution paradigm. However, the interpretation of the results in terms of pathophysiological mechanisms is not straightforward. We tested whether clinical phenotype and photoreceptor-specific sensitivity loss are correlated.
Methods :
Fourteen patients with retinitis pigmentosa participated in this study. They were categorized into five different groups according to funduscopy, OCT, and fundus autofluoresence (hyperreflective ring on FAF and normal ellipsoid zone (EZ) in the center: n=5, abnormal central EZ: n=3, cystoid macular edema: n=3, female carriers of RPGR mutations with typical FAF: n=2, choroideremia: n=1).
Flicker detection thresholds of L-, M-, S-cone- and rod isolating stimuli (294 phot Td mean retinal illuminance) were determined with an LED stimulator. We calculated sensitivity losses in dB compared with age-corrected normal values and averaged sensitivity losses at 1, 2, and 4Hz . Permutation analysis based on Euclidean distances in 3D space (L-cone-, S-cone-, and rod-sensitivities) was performed to test whether phenotypes were clustered.
Results :
L- and M-cone sensitivity losses were strongly correlated, so that the M-cone loss data were not included in the analysis. Our categorization according to phenotype resulted in significantly smaller distances within groups compared with random classification (p = 0.0325, 10000 permutations).
Conclusions :
Our results show that photoreceptor-specific sensitivity losses mediated by the color and the rod system correlate with the clinical phenotype. Compared with existing measures of photoreceptor-specific retinal function, our technique has the advantage that temporal frequency and retinal illuminance can be varied and that state of retinal adaptation is identical for all photoreceptor types. This offers interesting opportunities to investigate how photoreceptor damage affects processing in the (normal) inner retina and which implication this has for functional tests.
This is a 2020 ARVO Annual Meeting abstract.