Retinal vessel oxygen saturation and vessel diameter in retinitis pigmentosa

Purpose: To assess retinal vessel oxygen saturation and retinal vessel diameter in retinitis pigmentosa. Methods: A retinal oximeter (Oxymap ehf., Reykjavik, Iceland) was used to measure retinal vessel oxygen saturation and vessel diameter in ten patients with retinitis pigmentosa (RP) (mean age 49 years, range 23-71 years). Results were compared with age-and gender-matched healthy individuals. All patients had advanced stage of the disease with visual fields restricted to the macular region. Results: Oxygen saturation in retinal venules was 58.0 +/- 6.2% in patients with RP and 53.4 +/- 4.8% in healthy subjects (p = 0.017). Oxygen saturation in retinal arterioles was not significantly different between groups (p = 0.65). The mean diameter of retinal arterioles was 8.9 +/- 1.6 pixels in patients with RP and 11.4 +/- 1.2 in healthy controls (p < 0.0001). The corresponding diameters for venules were 10.1 +/- 1.2 (RP) and 15.3 +/- 1.7 (healthy, p < 0.0001). Conclusions: Increased venous saturation and decreased retinal vessel diameter suggest decreased oxygen delivery from the retinal circulation in retinitis pigmentosa. This is probably secondary to tissue atrophy and reduced oxygen consumption.