The Effect of Hyperoxia on Retinal Capillary Blood Flow in Mild-to-Moderate Non-Proliferative Diabetic Retinopathy

Abstract

Abstract: : Purpose: The study investigated the effect of manipulating blood oxygen levels on retinal capillary blood flow in patients with diabetes and non-diabetic controls; the induced change in retinal blood flow was compared between the groups. Methods: The sample comprised 11 patients with mild-to-moderate non-proliferative diabetic retinopathy (mean age 58.1 years, SD 6.84 years) and 11 non-diabetic controls (mean age 50.4 years, SD 4.5 years). One eye was randomly assigned to the study. Volunteers underwent a clinical examination, including the assessment of visual acuity and a comprehensive medical retina exam, and a hyperoxic provocation visit. Blood glucose and blood pressure were measured immediately prior to, and immediately after, hyperoxic provocation. Retinal capillary blood flow measurements were undertaken using the Heidelberg Retina Flowmeter (HRF). Four baseline HRF images, centered on the fovea, were acquired while breathing room air and 4 further images were acquired while breathing pure oxygen for a minimum period of 10 minutes. Results: The group mean reduction in retinal capillary blood flow as a result of hyperoxic provocation was 13.60% (SD 17.25, range –20.83 to 38.19%) and 8.59% (SD 10.59, range -14.1 to 24.75%) for the diabetic and non-diabetic groups, respectively. HRF assessment showed that hyperoxia resulted in a statistically significant reduction of retinal capillary blood flow for both the diabetic and non-diabetic groups (Students t-test, p0.05) difference in the response to hyperoxia between the groups. Conclusions: Using the HRF, hyperoxia resulted in a statistically significant reduction of retinal capillary blood flow for both the diabetic and non-diabetic groups. However, the magnitude (and direction) of the response varied substantially and the technique was unable to detect any difference in the capillary response to hyperoxia between the groups.

Keywords: diabetes • diabetic retinopathy