Early impairment of the full-field photopic negative response in patients with Stargardt disease and pathogenic variants of the ABCA4 gene

BACKGROUND: To study the photopic negative response of the full-field photopic ERG in Stargardt patients with pathogenic variants in the ABCA4 gene. METHODS: A retrospective analysis of 35 Stargardt patients with ABCA4 gene pathogenic variants, compared to normal age matched controls. Patients were clinically followed at the Ophthalmology Department of Fondazione Policlinico Universitario A. Gemelli/Università Cattolica del Sacro Cuore - Rome, Italy. RESULTS: The photopic negative response of the full-field photopic ERG was compromised in most Stargardt patients. In the presence of a normal B-wave, the amplitude ratio between the photopic negative response and the B-wave displayed a 97% accuracy in detecting diseased eyes (ROC curves). CONCLUSIONS: In Stargardt patients with ABCA4 pathogenic mutations, the photopic negative response of the full-field photopic ERG is a very sensitive disease read-out. Its inclusion in standard ERG analysis would be a no-cost addition of practical consequence in the follow-up of Stargardt disease. The early impairment of the photopic negative response suggests that inner retinal function might be affected in Stargardt disease earlier than previously acknowledged.