Abnormalities in Cone-mediated ERGs in Eyes of Patients with Fundus Albipunctatus with RDH5 Mutations

Abstract

Abstract: : Purpose: Recent studies have shown that the RDH5 gene, which encodes 11-cis-retinol dehydrogenase, is required for the regeneration of both rod and cone visual pigments. We studied the cone-mediated ERGs in patients with fundus albipunctatus (FA) from RDH5 mutations. Methods: Eight patients with FA were studied (5 men and 3 women; age, 10-55, mean, 24.3). Genomic analysis showed that all patients had mutations in the RDH5 gene. FA patients associated with cone dystrophy or maculopathy (Miyake et al, 1992; Nakamura et al, 1999) were excluded. Cone-mediated ERGs (single-flash cone and 30-Hz flicker responses) were recorded under a rod-desensitizing background. These ERGs were recorded immediately after a light-adapting light was turned and after 10 minutes of light adaptation. The amplitudes were compared to those from 20 age-matched controls. Results: The amplitude of cone ERGs in the FA group did not differ significantly from controls when recorded at the beginning of light adaptation (single-flash; FA=80.1±20.0, control=80.0±14.6 mV, 30-Hz; FA=28.4±8.8, control=31.3±8.4 mV). However, the amplitudes were significantly smaller than controls when recorded after 10 minutes of light adaptation (single-flash; FA=87.5±32.0, control=122.6±28.9 mV, 30-Hz flicker; FA=26.5±16.2, control=38.2±10.7 mV). The percentage increase of the cone ERG amplitude during 10 minutes of light adaptation was significantly lower in FA (single-flash; 109%, 30-Hz flicker; 92%) than in the controls (single flash; 154%, flicker; 122%). Conclusions: Cone-mediated ERGs in FA were significantly smaller than those of controls when recorded after 10 minutes of light adaptation. These results might be caused by the abnormal recovery kinetics of cone visual pigments due to RDH5 mutations.

Keywords: electroretinography: clinical • gene mapping • retinal degenerations: hereditary