Change of retinal oxygen saturation in healthy subjects and in early stages of diabetic retinopathy during breathing of 100 % oxygen

Background: Disturbances in the microcirculation are a Source Of retinal diabetic alterations. Comprehensive studies of blood flow parameters have been performed, but it is not known how ageing, duration of diabetes, blood sugar, glycolysed haemoglobin and elevated systemic blood pressure act in the early stages of diabetic retinopathy. Material and Methods: The arterial and venous oxygen saturation (aOS, vOS) were measured with a Jena Ophthalmo Spectrometer in 28 healthy subjects (NP) (30.3 + 13.1 years), 31 Type I diabetics (TI) (42.2 +/- 12.9 years), and in 25 Type II diabetics (TII) (58.9 +/- 6.9 years), suffering form mild or moderate non-proliferative diabetic retinopathy, before, during breathing of 100% oxygen for 6 minutes, and after respiration of air during 10 minutes. Results: Before oxygen breathing, the venous oxygen saturation in diabetics increased with age. During breathing of 100% oxygen, the vOS increased considerably by 20% in all groups. The arterio-venous difference of oxygen saturation was decreased with age in diabetics, but there was no dependence on age in normals. In Type II diabetics, the vOS before oxygen breathing was increased with HbA1c. There was also a positive Correlation between vOS and blood pressure before oxygen breathing. Conclusion: Healthy subjects and diabetics in the early stages of diabetic retinopathy exhibit comparable changes of oxygen saturation during breathing of 100% oxygen. Measurements of venous OS are most evident. First differences were detectable between diabetics and normals in the normalisation after oxygen respiration.