Effects of insulin on retinal and pulsatile choroidal blood flow in humans

Abstract

Background: Insulin induces vasodilation in several tissues, including skeletal muscle and kidneys. Objective: To investigate whether insulin may contribute to ocular blood flow regulation. Methods: The study was performed in a balanced, randomized, placebo-controlled, single-masked, 3-way, crossover design in 9 healthy male subjects. Each subject received 2 doses of insulin (1.5 or 3 mU/kg per minute) or placebo on 3 different study days. Measurements of fundus pulsation amplitude with laser interferometry to assess pulsatile choroidal blood flow, of retinal blood flow with the blue- field entoptic technique, and of mean blood flow velocity in the ophthalmic artery with Doppler sonography were performed under euglycemic clamp conditions over 120 minutes. Results: Hyperinsulinemia significantly increased fundus pulsation amplitude (1.5 mU/kg per minute: 8.7% ± 1.1% vs baseline; 3 mU/kg per minute: 13.2% ± 2.3% vs baseline; P