Choroidal Vasculature in Bietti Crystalline Dystrophy With CYP4V2 Mutations and in Retinitis Pigmentosa With EYS Mutations

We compare the choroidal vascular area between Bietti crystalline dystrophy (BCD) patients with CYP4V2 mutations, retinitis pigmentosa (RP) patients with EYS mutations, and normal controls, and investigate the correlation between choroidal vascular area and associated parameters. This prospective case-series study included consecutive nine eyes of nine BCD patients with CYP4V2 mutations (BCD group), 16 eyes of 16 RP patients with EYS mutations (EYS-RP group), and 16 eyes of 16 normal volunteers matched for age and axial length (control group). Using swept-source optical coherence tomography, we obtained en face images of the choroidal vasculature at the midpoint of the choriocapillaris layer-Sattler's layer (inner choroid) and Haller's layer (outer choroid). After binarization, we compared the inner and outer choroidal vascular areas among the three groups and identified associated factors. The outer choroidal vascular area was 43.34 ± 5.76%, 53.73 ± 4.92%, and 52.80 ± 4.10% in the BCD, EYS-RP, and control groups, respectively. This value was significantly smaller in the BCD group than in the EYS-RP and control groups (P < 0.001 in both; no significant difference between the EYS-RP and control groups). In the BCD group, the outer choroidal vascular area was correlated strongly with the subfoveal inner choroidal thickness (P = 0.001, r = 0.91, respectively). The inner choroidal vasculature could not be identified in eight of nine eyes in the BCD group. The outer choroidal vascular narrowing might progress with the inner choroidal thinning in BCD, and the inner choroidal vasculature might be extinguished in advanced-stage BCD. Our findings may help to clarify the etiology of BCD.