Sorsby's fundus dystrophy: A case report of 24 years follow-up with electrodiagnostic tests and indocyanine green angiography

Abstract

Five families with dominantly inherited macular dystrophy were originally described by Sorsby et al. in 1949. Key features include early bilateral central visual loss secondary to either choroidal neovascularisation or central geographical atrophy and late progressive chorioretinal atrophy. We report a member of one of the original families who has been studied with a series of investigations over a long time, providing important information on differences in the phenotype and natural history of a rare genetically determined macular dystrophy. The patient has been followed up for the last 24 years, from asymptomatic to full manifestation of Sorsby's fundus dystrophy. Series of fundus photographs, colour vision, dark adaptation and electrodiagnostic tests were performed. The disease was also studied with fundus fluorescein angiography and indocyanine green angiography. Unlike her other family members, who were reported in other studies as all having rapid loss of vision secondary to disciform macular disease, our patient has a unique clinical course in that she has a progressive bilateral central and generalised chorioretinal atrophy with a well-preserved minute central island of fovea. Nyctalopia was her early and only symptom. There was evidence of central scotoma, tritanopia and mild abnormality in dark adaptation. Rod function was affected earlier and to a larger degree than cone function. The overall features suggest phenotypic variability within a family in this autosomal dominant macular dystrophy. The findings from indocyanine green angiography and a consecutive series of electrodiagnostic tests in this condition support the theory of partial choroidal hypoperfusion and an interesting progressive rod-cone dystrophy as part of the pathophysiology.