Purpose: To assess photoreceptor integrity in patients with retinitis pigmentosa (RP) and related diseases using ultra-high resolution optical coherence tomography (UHR-OCT) and to correlate foveal photoreceptor loss with visual acuity. Design: Observational case series. Methods: Nine eyes of nine patients with RP and related diseases were imaged with UHR-OCT at the ophthalmology clinic. Patients were diagnosed based on history, examination, fluorescein angiography, and electroretinography. Concurrently, 36 eyes of 36 normal subjects were imaged with UHR-OCT. Central foveal thickness (CFT) and foveal outer segment/pigment epithelium thickness (FOSPET) were defined and measured on UHR-OCT images in all subjects and were compared between the two groups using unpaired t tests. The two thickness measurements in RP patients were correlated with visual acuity using Pearson correlation and linear regression. Results: UHR-OCT demonstrated macular photoreceptor thinning in all RP patients. The difference in CFT between RP patients and normal subjects was not statistically significant (P = .103), but the difference in FOSPET between the two groups was significant (P = .003). Visual acuity showed a fair correlation with CFT (Pearson r = -0.43, r2 = 0.187, P = .245) and an excellent correlation with FOSPET (Pearson r = -0.942, r2 = 0.887, P < .0001). Conclusions: In the current study using UHR-OCT, a new thickness measurement termed FOSPET is demonstrated to quantify photoreceptor loss. FOSPET was statistically thinner in patients with RP and related diseases than in normal eyes and showed correlation with logMAR visual acuity. FOSPET appears to be a probable predictor of visual acuity in RP.
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