Relationship between Preserved Ellipsoid Zone Area and Choroidal Vascularity Index in Autosomal Dominant Retinitis Pigmentosa

Background: Retinitis Pigmentosa (RP) is characterized by changes in the outer retina as well as the choroid. In this study, we sought to further elucidate the longitudinal relationship between the preserved Ellipsoid Zone (EZ) area and choroidal parameters, in particular the Choroidal Vascularity Index (CVI). Patients and methods: Spectral Domain OCT (SD-OCT) volume scans of 48 eyes of 24 subjects with autosomal dominant RP (ADRP) were collected retrospectively at baseline and month 12. Spectralis Heidelberg Retinal Angiogram (HRA+OCT) scans (20*20 degrees;512*97;ART=5) were acquired at both visits. A previously described and validated Doheny Image Reading Center (DIRC) OCT grading software (OCTOR) was used to manually delineate the inner and outer boundaries of the EZ layer and the choroid. The sub foveal choroidal thickness (CT) was manually calculated and the CVI was measured. The parameters were compared and correlated at baseline and month 12 using paired t-tests and bivariate correlations. Results: The mean preserved EZ area (P=0.02) and the mean CT (P=0.007) showed a significant decline from baseline to month 12, but no correlation was noted between them. There was no significant difference in CVI from baseline to month 12. Despite these results, the loss of preserved EZ area was seen to be correlated to the CVI at both the baseline and month 12. Conclusion: The rate of disease progression, as assessed by loss of EZ, was correlated with CVI. These observations highlight the relevance of choroidal alterations in the progression of RP.