Direct comparison of retinal structure and function in retinitis pigmentosa by co-registering microperimetry and optical coherence tomography

Purpose To evaluate the retinal structure-function relationships in the macula of retinitis pigmentosa (RP) patients by comparing microperimetry-3 (MP-3) images with co-registered optical coherence tomography (OCT) images. Methods Thirty patients with typical RP were recruited from our hospital. The maculae of patients were examined with MP-3 and OCT. The retinal sensitivity was measured by MP-3 at 40 testing points arranged concentrically in a 16∘ diameter of the central retina, and we divided the 40 points into four zones according to degree from the fovea (2∘, 4∘, 6∘, and 8∘). We analyzed the correlation coefficients between the retinal sensitivity and the total retinal thickness (TRT), the length from the inner limiting membrane to the retinal pigment epithelium (RPE), and between the retinal sensitivity and the outer retinal thickness (ORT), the length from the outer plexiform layer to the RPE at each stimulus point. Results TRT showed moderate correlations with the retinal sensitivity at 2∘ (median ρ = 0.59 interquartile range (IQR) [0.38–0.72]), 4∘ (ρ = 0.59 [0.55–0.68]) and 6∘ (ρ = 0.60 [0.54–0.63]), and TRT was weakly-to-moderately related to the retinal sensitivity at 8∘ (ρ = 0.27 [0.19–0.48]). ORT exhibited strong correlations at 2∘ (ρ = 0.72 [0.60–0.81]), 4∘ (ρ = 0.71 [0.75–0.67]) and 6∘ (ρ = 0.70 [0.54–0.74]), and a weak-to-moderate correlations at 8∘ (ρ = 0.34 [0.29–0.53]). ORT was more strongly correlated with the retinal sensitivity compared to TRT (p = 0.018). Conclusion ORT, rather than TRT, within 6∘ eccentricity was strongly correlated with the retinal sensitivity, suggesting that measuring ORT in those areas will help evaluate the macular status and progression in RP.