Inter-Eye Symmetry in Bietti Crystalline Dystrophy.

Abstract

To evaluate anatomical and functional inter-eye symmetry among individuals with Bietti Crystalline Dystrophy (BCD) using clinical and multi-modal imaging methods, with a focus on the number, area, and distribution of the characteristic retinal crystalline deposits. Observational case series with prospective and retrospective data. Setting: Multicenter STUDY POPULATION: Thirteen Australian and New Zealand participants (26 eyes) with confirmed biallelic CYP4V2 mutations and a characteristic BCD fundus appearance. Crystals visible on color fundus photography were manually counted. Crystals were superimposed on aligned multimodal fundus images. Spearman's correlation coefficients (ρ), intraclass correlation coefficients (ICCs), and Bland-Altman plots were used to quantify symmetry between eyes. Fundus crystal area and count, and absent-autofluorescence (absent-AF) area. Median participant age was 48 years, interquartile range 40-60 years. Inter-eye symmetry was high for fundus crystal area (ρ=1.00, 95% CI 1.00-1.00; ICC=0.97, 95% CI 0.88-0.99), fundus crystal count (ρ=0.98, 95% CI 0.92-1.00; ICC=0.97, 95% CI 0.89-0.99), and absent-AF area (ρ=0.88, 95% CI 0.53-0.98; ICC=0.98, 95% CI 0.90-0.99). Average foveal volume, foveal crystal count and area, average and central foveal thickness, best corrected visual acuity, and average macular and central foveal sensitivity were not highly correlated between eyes. This study demonstrated strong inter-eye symmetry measured by fundus crystal area, fundus crystal number, and absent-AF area. This may influence the choice of outcome measures for future therapeutic trials for BCD, and provides valuable clinical information for ophthalmologists involved in the care and counselling of BCD patients.