Oxygen saturation in the retinal vessels of glaucoma and normal eyes

Objective To observe the difference of retinal vessel oxygen saturation in glaucoma and normal eyes. Methods A cross sectional study design was performed. Fifty eyes of 30 glaucoma patients (glaucoma group) and 41 eyes of 27 age- and sex-matched healthy subjects (control group) were included. Retinal vessel oxygen saturation was measured with a spectrophotometric retinal oximeter in darkness and visual fields were obtained by Humphrey filed analyzer. The glaucoma eyes were divided into two groups: mean defect (MD) <6 dB (28 eyes) and MD≥6 dB (22 eyes) according to mean defect of visual field. Results Retinal arteriolar oxygen saturation values in glaucoma group and control group were (94.52±6.51)% and (93.47±6.30)% respectively. No statistical difference was found in retinal oxygen saturation in arterioles (H=-0.949, P=0.343). Retinal venous oxygen saturation values in glaucoma group and control group were (57.57±7.96)% and (52.60±7.70)% respectively. The retinal venous oxygen saturation values in glaucoma group was higher than that in control group (H=-3.318, P=0.001). The retinal arteriovenous difference in glaucoma group and control group were (36.59±4.69)% and (42.41±6.73)% respectively. The retinal arteriovenous difference in glaucoma group was lower than that in control group (H=-4.148, P<0.01). The retinal arteriolar oxygen saturation values in glaucoma eyes with MD<6 dB and MD≥6 dB were (93.38±6.33)% and (95.71±6.54)% respectively, with no statistical difference (H=-1.857, P=0.063). Retinal venous oxygen saturation values in glaucoma eyes with MD<6 dB and MD≥6 dB were (54.83±6.10)% and (61.07±8.79)% respectively. The retinal venous oxygen saturation values in MD≥6 dB glaucoma eyes was higher than that in MD<6 dB glaucoma eyes (H=-2.599, P=0.009). The retinal arteriovenous difference in glaucoma eyes with MD<6 dB and MD≥6 dB were (38.12±4.34)% and (34.64±4.49)% respectively. The retinal arteriovenous difference in MD≥6 dB glaucoma eyes was lower than that in MD<6 dB glaucoma eyes (H=-2.463, P<0.05). Conclusions Compared with healthy eyes, there is no change in the retinal arteriolar oxygen saturation, but the retinal venous oxygen saturation is higher and the retinal arteriovenous difference is lower. This feature is more obvious in MD≥6 dB glaucoma eyes. Key words: Glaucoma/etiology; Oximetry