Improved Metabolic Control Results in Better Myogenic Response of Retinal Arterioles in Patients with Diabetes Mellitus Type 1

Abstract

Aims: The retina is protected against high blood pressure by the myogenic constriction of arterioles (the Bayliss effect). Hyperglycemia impairs this retinal autoregulation by endothelial dysfunction. The purpose of this prospective pilot study was to test whether improved metabolic control results in a measurable effect on the myogenic response of human retinal arterioles to acute increases in blood pressure. Methods: The Bayliss effect was measured in 25 patients with diabetes mellitus by the Retinal Vessel Analyzer (RVA), both before and after participation in a treatment and teaching program for intensified insulin therapy with the goal of improved metabolic control. After 12 months, 17 subjects still fulfilled the inclusion criteria and underwent an identical measurement. The Wilcoxon test was used for statistical analysis. Results: During the first session, a rise in mean arterial pressure (MAP) of 20.2 ± 8.6 mm Hg was followed by an arterial vasoconstriction of –3.2 ± 2.9%. The educational program resulted in a significant drop in Hb_A1c levels (9.4 ± 1.9 vs. 6.9 ± 0.98%). Eight subjects did not meet the inclusion criteria after 12 months. Seventeen subjects were remeasured and a rise in blood pressure of 19.5 ± 9.9 mm Hg in the second session was associated with a significantly improved arterial vasoconstriction of –5.9 ± 2.7% (session I vs. session II, p = 0.006). Conclusion: The myogenic response of the arterial wall in human retinal arterioles was significantly improved by the therapeutic intervention.