Quantitative Choroidal Analysis of Molecularly Characterized Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a genetically diverse progressive retinal degeneration with many biomarkers. Detailed retinal phenotypes are described using multimodal imaging, however choroidal characteristics remain ill-defined. We report the first quantitative choroidal evaluation in molecularly characterized RP and assess relationships with retinal structure and function.

Patients with genetically confirmed RP who had optical coherence tomography images and best-corrected visual acuity (BCVA) were assessed. Optical coherence tomography images were manually segmented (ITKSnap) calculating choroidal thickness (CT), choroidal area (CA), and choroidal volume (CV). The choroidal vascularity index (CVI) was calculated with ImageJ. Comparisons were made between X-linked (RPGR), autosomal-recessive (USH2A), and autosomal-dominant (RHO, PRPF31) genotypes, including comparisons for choroidal/retinal parameters, BCVA, and spherical equivalent (SE).

Sixty-five patients (mean age, 47.3 ± 19.5 years; 52.3% female) met the inclusion criteria. CT was thinner in RP patients than controls (P = 0.003). A thinner choroid was associated with older age (r = -0.512; P < 0.001) and worse BCVA (r = 0.298, P = 0.002) but not SE (P = 0.194). Although variable, no statistically significant differences were found for choroidal measures between groups. Leptochoroid (≤100 µm) was associated with advanced age (P < 0.001) and worse BCVA (P = 0.032), but not greater myopia (P = 0. 533). Greater CVI was only associated with better BCVA (P < 0.001) and no other parameters.

We report the first quantitative choroidal assessment in a cohort with genetically characterized RP. CT changes in RP are not explained solely by age-related choroidal thinning, nor by SE but seem to be dynamic and reactive to degree and rate of retinal degeneration.