The effects of nitroglycerine and COX‐inhibition on retinal vessel diameters during hypoxia

Abstract

PurposeRetinal hypoxia plays a role in the pathophysiology of retinal vascular diseases such as diabetic retinopathy. Previous studies have shown that nitric oxide (NO) and cyclooxygenase (COX) products are involved in hypoxia‐induced dilatation of the retinal vessels. Therefore, the purpose of this study was to examine the effect of an NO donor and inhibition of COX products on the diameter regulation of retinal vessels during hypoxia in healthy subjects.MethodsTwenty normal persons were examined with the Dynamic Vessel Analyzer (DVA). Retinal vessel diameters were measured at rest, and during isometric exercise and flicker stimulation. The measurements were performed during normoxia and hypoxia before and after sublingual administration of the NO donor nitroglycerine, and were repeated on a second study day after topical administration of the COX‐inhibitor diclofenac.ResultsHypoxia alone and combined with nitroglycerine significantly reduced both arteriolar constriction during isometric exercise and dilatation during flicker stimulation (p < 0.0001). Diclofenac further reduced the arteriolar constriction induced by isometric exercise during hypoxia (p = 0.005). Nitroglycerine alone had no effect on the retinal vessel diameters.ConclusionsDiameter regulation of retinal vessels during hypoxia in normal persons is affected by inhibition of COX products but not by increased NO. The results contribute to understanding of retinal flow regulation and thereby to the identification of possible new strategies for intervention on diseases characterized by disturbances in retinal blood flow.