Analysis of retinal vessels in eyes with retinitis pigmentosa by retinal oximeter

Purpose: To study changes in the oxygen saturation and calibre of retinal vessels in the eyes of patients with retinitis pigmentosa (RP). Method: In this cross-sectional study, 63 eyes of 63 patients with RP and 14 eyes of 14 healthy subjects were enrolled and examined at Toyama University Hospital. Retinal oximetry measurements were performed using a spectrophotometric oximetry unit (Oxymap T1, Reykjavik, Iceland), which is coupled to a fundus camera base (TRC-50DX; Topcon Corporation, Tokyo, Japan). Retinal arterioles of 28 eyes and retinal venules of 35 eyes with adequate image quality were selected for analyses. We calculated the residual areas of visual field (I-4e and V-4e isopters) in each eye and determined the correlations between the data of retinal vessels and the areas of visual field in the RP eyes. Results: The mean oxygen saturation of the venules in the RP eyes (60.2 +/- 6.5%) was significantly higher than that in healthy eyes (54.6 +/- 6.3%, p = 0.0089). The oxygen saturation of the venules in the RP eyes correlated significantly with the residual areas of the visual field of V-4e (r = -0.50; p = 0.0030). The mean calibres of the retinal arterioles (91.1 +/- 9.1 mu m) and retinal venules (116 +/- 13 mu m) of the RP eyes were significantly narrower than those of the healthy eyes (115 +/- 11 mu m and 152 +/- 15 mu m, respectively, p < 0.01). The retinal arteriolar and venular calibres in the RP eyes correlated with the residual areas of the visual field of V-4e (r = 0.43; p = 0.033 and r = 0.45; p = 0.011, respectively). Conclusions: The severity of RP was correlated with increased oxygen saturations in the retinal venules and decreased retinal vessel calibres.