Multifocal electroretinogram in the diagnosis of Stargardt disease

Aims/Purpose: Electrophysiological vision tests have been a key method in the diagnosis and monitoring of inherited retinal dystrophies (IRD). With the development of mfERG, the clinical applications of these tests have expanded to cone dystrophies such as Stargardt disease, which is the most common cone‐IRD. This disease is typically associated with an autosomal recessive inheritance pattern, primarily, although not exclusively, due to mutations in the ABCA4 gene. The introduction of different diagnostic techniques such as Optical Coherence Tomography (OCT), OCT Angiography (OCTA), autofluorescence (FAF) and microperimetry has diminished the importance of fluorescein angiography (FA). These techniques have been joined by the diagnostic role of mfERG.The aim of this study is to evaluate functional changes in patients with Stargardt disease using mfERG.Methods: Eighteen eyes of patients with Stargardt disease were included. The disease was previously confirmed by genotyping with homozygous ABCA4 mutations or heterozygous PROM1 mutations. The patients were evaluated using mfERG, using the standardized international ISCEV guidelines. Electrical density and implicit time of each first‐order response (K1) in the five concentric rings centered on the fovea were measured and analysed.Results: Mean best‐corrected visual acuity (BCVA) was 0.5 (0.12–1.0). First‐order responses (K1) showed a decreased electrical density, predominantly in central rings, along with minimally prolonged latencies of the P1. FAF showed central atrophy in 6 patients, atrophy with flecks within or beyond the vascular branches in 8 and 4 patients respectively.Conclusions: Stargardt disease involves cones and is characterized by a significant decrease in foveal and central response in mfERG, even in early stages when BCVA remains relatively preserved and fundus findings are minimal. Flash ERG may show normal results or minimal abnormalities.