Relationship of Blood Pressure to Retinal Vessel Diameter in Type 1 Diabetes Mellitus

Objective: To examine the relationship of blood pressure (BP) and use of angiotensin-receptor blocker or angiotensin-converting enzyme inhibitor to retinal vessel diameter in normotensive, normoalbuminuric persons with type 1 diabetes mellitus. Methods: In a randomized, controlled clinical trial, clinic and 24-hour ambulatory BPs were measured in persons with type 1 diabetes mellitus and gradable fundus photographs both at baseline (n = 147) and at 5-year follow-up (n = 124). Retinal arteriole and venule diameters were measured by a computer-assisted technique. Individual arteriole and venule measurements were combined into summary indexes that reflect the average retinal arteriole (central retinal arteriole equivalent [CRAE]) and venule (central retinal venule equivalent [CRVE]) diameter of an eye, respectively. Results: While controlling for age, study site, glycosylated hemoglobin level, and ambulatory pulse rate, the daytime ambulatory systolic (-0.29-mu m effect per 1 mmHg; P= . 02), daytime ambulatory diastolic (-0.44-mu m effect per 1 mm Hg; P= . 04), nighttime ambulatory systolic (-0.27-mu m effect per 1 mm Hg; P = .03), and 24-hour ambulatory systolic (-0.31-mu m effect per 1 mm Hg; P = .03) BPs were cross-sectionally associated with a smaller CRAE. While controlling for age, study site, glycosylated hemoglobin level, ambulatory pulse rate, and baseline CRAE, no BP measure was associated with a change in CRAE or CRVE during 5 years of follow-up. Treatment with losartan potassium or enalapril maleate was not associated with a statistically significant change in CRAE or CRVE. Conclusion: Angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker therapy does not affect retinal arteriole or venule diameter in normotensive persons with type 1 diabetes mellitus.