Correlation of clinical phenotype with multifocal ERGs in patients with Stargardt disease/fundus flavimaculatus

Abstract

Abstract: : Purpose: The purpose of the present investigation is to identify and describe any correlation between the clinical phenotype and multifocal electroretinograms in a series of 18+ patients with Stargardt disease/fundus flavimaculatus. The investigators hypothesize that the phenotype of a patient is predictive of retinal dysfunction, primarily involving the outer rings of the mfERG. Methods: Eighteen patients with Stargardt disease/fundus flavimaculatus were identified in the retina services of two tertiary care facilities. Dilated fundus photographs were obtained and patients were then categorized by fundus appearance into two primary phenotypic subgroups. Multifocal ERGs were obtained according to previously published standards. Latencies and amplitudes were calculated for each ring and an average of both eyes was calculated. The two phenotypic categories were compared with the a series of normal controls from one lab using one–way ANOVA. Phenotype I was then compared to phenotype II–III. Linear regression was used within each subgroup to determine if the age of the patient could explain any variation in the retinal function. Results: A total of nine patients with phenotype I (macular degeneration only), nine patients with phenotype II–III (macular degeneration with parafoveal or diffuse flecks), and seven normal controls were identified. Patients with phenotype I demonstrated decreased peak amplitudes and increased latencies for all six rings, with the exception of the latencies in rings 1 and 2 (all p < 0.05). Patients with phenotype II–III demonstrated decreased peak amplitudes and increased latencies for all six rings (all p < 0.05). When comparing phenotype I to phenotype II–III, there was a trend for decreased amplitudes and increased latencies in the phenotype II–III group, but this was statistically significant only for the amplitude in ring 1 and the latency in ring 2. Age does not appear to predict retinal dysfunction within the phenotypic subgroup with one exception—age describes 63% of the variation in latency in ring one for patients with phenotype I (p < 0.011). Conclusions: The results confirm that the retinal function in patients with SD/FF is diffusely depressed compared to normal controls. The investigators suspected the outer rings of patients with phenotype II–III would demonstrate lower amplitudes and prolonged implicit times than patients with phenotype I. The results demonstrate that trend, but are only statistically significant for the amplitude of ring 1 and the implicit time of ring 2.

Keywords: retinal degenerations: hereditary • degenerations/dystrophies • electroretinography: clinical