Abstract
Purpose:
Retinitis pigmentosa (RP) is a spectrum of inherited retinal degenerations caused by degeneration of photoreceptors cells. It is not well known whether the choroid is sequentially affected with progressive degeneration of photoreceptors. This study analyzed the choroidal thickness in patients with RP with varying disease severity and compared it to the retinal thickness using the newest technology of swept source optical coherence tomography (SS-OCT).
Methods:
Fourteen eyes of 7 patients with RP were included in this retrospective study. There were 5 men and 2 women with a mean age of 50.6 years (median - 53 yrs, range 29 - 75 years). Patients with other systemic conditions that can affect the retinal or choroidal thickness were excluded from the study. All patients had SS-OCT performed on both eyes by a single operator using the DRI-OCT-1(Topcon, Tokyo, Japan). All subjects had 12 mm X 9 mm radial and 5 line scan centered at the fovea. The choroidal and retinal thickness map contained three concentric rings of diameter 1, 3, and 6 mm with center at fovea. The choroidal and retinal thickness were measured in the 9 Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, including central subfield (CSF). All subjects had retinal image quality of ≥75% and choroidal image quality of ≥80%. The retinal thickness measured by this instrument measures from the internal limiting membrane up to the RPE but not including RPE. A correlation analysis was done between the retinal thickness and choroidal thickness in all 9 segments, using Graph Pad Instat3 (San Diego, CA).
Results:
The mean retinal and choroidal thickness was 242.6μ and 166.1μ, respectively. Although the retinal thickness was in the normal range, the choroidal thickness was markedly decreased as compared to normals from our population (about 250μ). There was no correlation between the relative thicknesses of the retina and the choroid.
Conclusions:
This pilot study with the newest technology of swept source OCT showed that choroidal thickness was decreased out of proportion to the retinal thickness in patients with retinitis pigmentosa. Studying this in a larger population in this group of patients maybe helpful to elucidate the pathogenesis of this inherited condition.