Purpose: Hyperreflective foci (HRF) in the outer retina are associated with the progression of multiple retinal diseases, but their pathogenic significance in retinitis pigmentosa (RP) remains obscure. We studied outer retinal HRF number and distribution in RP using spectral-domain (SD) OCT and assessed associations with visual field loss, retinal inflammation, and photoreceptor degeneration. Design: Retrospective cross-sectional study. Participants: Medical records of 128 eyes of 66 RP patients (mean age, 45.7±16.1 years; range, 10–85 years). Methods: All participants underwent high-resolution SD-OCT. Outer retinal HRF were counted on vertical and horizontal SD-OCT images centered at the fovea of 55 eyes of 29 patients. In addition, SD-OCT macular volume scans of 92 eyes of 48 patients were reviewed and compared with fundus autofluorescence images of the same area to investigate outer retinal HRF distribution and the spatial relations to areas of low autofluorescence and photoreceptor inner segment and outer segment junction (IS/OS) preservation. Main Outcome Measures: The number and distribution of outer retinal HRF, aqueous flare value, thickness of outer layers, visual field area, and fundus autofluorescence. Results: In the HRF counting analysis, the mean number of outer retinal HRF per scan was 24.0±18.6, mean aqueous flare value was 7.7±3.2 photon count/ms, visual field area was 25.2±26.6%, and thickness of the outer layers was 95.2±39.6 μm. Generalized estimating equations revealed that the number of outer retinal HRF was associated positively with aqueous flare value (P = 0.01) and associated negatively with visual field area and outer layer thickness (P = 0.016 and P < 0.001, respectively). In the distribution analysis, macular areas exhibiting outer retinal HRF (HRF areas) spatially overlapped with areas of low autofluorescence. In contrast, HRF areas did not overlap with areas showing preserved IS/OS. Conclusions: Outer retinal HRF number is associated with intraocular inflammation and photoreceptor degeneration in RP. Their distribution in areas with IS/OS disruption and low autofluorescence suggests that outer retinal HRF reflect defects in the retinal pigment epithelium (RPE) layer caused by RPE cell or microglial migration in response to photoreceptor degeneration.
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