Long-term effects of hyperbaric oxygen therapy on visual acuity and retinopathy

Hyperbaric oxygen (HBO2) therapy is an adjunct treatment for diabetic foot ulcers. Since plausible mechanisms of action for this treatment include increased angiogenesis and high tissue oxygen concentrations, concerns about deterioration of retinopathy have been raised. The aim of this study was to evaluate the effects of HBO2 on visual acuity (VA) and retinopathy in patients with chronic diabetic foot ulcers during a two-year follow-up period. This is a randomized, single-center, double-blinded and placebo-controlled clinical trial evaluating the effects of HBO2 in patients with diabetes mellitus and chronic foot ulcers. All study participants underwent an ophthalmological examination before the first study treatment and then at three, six, 12 and 24 months. Fifty patients with a median age of 67 years were included. Visual acuity was similar between groups and did not change during the two-year observation period. No differences in retinopathy were seen between groups; neither were any differences found in numbers or areas of bleedings, hard exudates, microaneurysms or edemas, nor between groups or visits. New clinically significant macular edema was identified in four eyes in the HBO2 group and in three eyes in the placebo group. In this population of diabetic foot ulcer patients HBO2 seems to be neutral in an ophthalmological perspective. From a retinal point of view, we could not identify any indication of harmful effects of HBO2 on the microvascular bed in the placebo group.