Purpose: To describe the morphologic and functional characteristics of subclinical Best vitelliform macular dystrophy (VMD) in subjects with mutation in the BEST1 gene.
Methods: Best-corrected visual acuity (BCVA), funduscopic appearance, fundus autofluorescence (FAF), spectral-domain optical coherence tomography (SD-OCT), and electro-oculography (EOG) were assessed in 23 consecutive subjects from nine unrelated families with known mutations in the BEST1 gene (eight distinct BEST1 mutations).
Results: Six subjects were identified with BEST1 mutations (three male, three female; aged 8 to 30 years) without clinically detectable (subclinical) Best VMD (absence of both symptoms and funduscopic lesions). All six subjects showed 20/20 BCVA and normal FAF findings. In these 6 of 26 subjects from five different families, we found five distinct mutations in the BEST1 gene. In three (six eyes) out of these six subjects with BEST1 gene mutations (two families: p.G15D; p.A243V), SD-OCT showed overall normal findings. In the other three subjects (six eyes) with BEST1 gene mutations (three families: p.V9A; p.R92C; p.I230T), we found, on SD-OCT, a thicker and more reflective appearance of the layer between the retinal pigment epithelium and the interface of inner segments and outer segments of the photoreceptor (the Verhoeff's membrane). EOG showed a reduced light-peak:dark-trough ratio in 5 of 12 eyes. Changes on SD-OCT were present in the absence of EOG abnormalities (two of six eyes), and vice versa (one of six eyes).
Conclusions: Subclinical Best VMD (absence of both symptoms and funduscopic lesions) in subjects with BEST1 mutation may vary from the absence of any morphologic and functional abnormalities to the presence of specific SD-OCT and EOG changes.