Grading severity in retinitis pigmentosa using clinical assessment, visual acuity, perimetry and optical coherence tomography

To develop a grading system for retinitis pigmentosa (RP), providing clinicians with a simple, objective measure of disease severity. An observational case series of 14 patients with RP. Disease severity was assessed using four criteria; clinical appearance, visual acuity (best corrected LogMAR, BCVA), perimetry (mean deviation, MD) and Fourier-domain optical coherence tomography (outer retinal thickness, ORT at the fovea). Each criterion was scored on a severity scale from 0 (mild disease) to 4 (severe disease), giving an overall score out of 16. The mean BCVA was 0.37 LogMAR (range 0.02 to PL), mean MD was −25.35 dB (range −7.48 to −34.38 dB), mean retinal thickness at the fovea was 189.4 μm (range 96.5−264.5 μm) and mean ORT at the fovea was 140.6 μm (range 63.4−193.4 μm). The clinical appearance correlated well with each of the quantitative measures of disease severity; BCVA (0.62, p = 0.022), MD (−0.903, p < 0.0001) and ORT (−0.698, p = 0.005). Applying the grading system to our patients, the severity scores were evenly spread between grades 1 and 14. We present a simple, objective grading system for RP offering a potential tool for grading disease severity with applications such as assessing progression, comparing patient populations and measuring outcomes in clinical trials.