Higher mean arterial blood pressure (MABP) has been consistently shown to be related to narrower retinal arterioles.1-6 Most studies showing this relation have been cross-sectional and involved general populations of middle to older-aged persons and individuals with hypertension. There are few studies which have examined whether increases in blood pressure (BP) over time are related to a subsequent decrease in the retinal arteriolar diameter and whether antihypertensive treatment affects retinal arteriolar and venular diameters.7-11 In a cross-sectional study in a general population, a history of use of an angiotensin-receptor-converting enzyme inhibitor (ACEI) was not related to retinal arteriolar or venular caliber.7 In the Anglo-Scandinavian Cardiac Outcomes Trial, involving 712 hypertensive individuals, despite similar blood pressure levels, persons randomized to a calcium channel blocker, amlodipine had a smaller arteriolar length to diameter ratio, a measure of retinal arteriolar narrowing, compared to those randomized to a beta blocker, atenolol.10 While the data suggest that blood pressure lowering is associated with a decrease in retinal arteriolar narrowing due to hypertension, it is not certain whether drugs, such as amlodipine, alters small artery structure independent of BP reduction during antihypertensive treatment. There were no differences in venular measures between treatment groups in this study. In another study involving non-diabetic hypertensive patients, treatment with losartan, an angiotensin-receptor blocker (ARB) led to an increase in the retinal arteriolar but did not affect the venular diameter.8 In a randomized controlled clinical trial in men with untreated hypertension, an ACEI, enalapril, but not a diuretic, hydrochlorothiazide, was shown to reduce narrowing of retinal arterioles.9 In a small study of 25 men with untreated hypertension randomized to treatment with an amlodipine or lisinopril over a one year period, blood pressure reduction using both treatments were associated with a reduction in arteriolar narrowing but had no effect on venular diameter.11 There are no comparable data on the effect of ACEI or ARB on retinal arteriolar diameter in normotensive persons with type 1 diabetes mellitus (T1DM). Understanding the relation of these drugs to retinal arteriolar narrowing and venular widening is important because the latter are thought to be markers of microvascular changes in the cerebral, coronary, peripheral, and renal circulations, and possibly of pathogenetic processes damaging to other targets of diabetic microvascular injury.4,5,12-20 In this report, we examine the relation of ACEI or ARB treatment and blood pressure to changes in retinal vessel caliber in a randomized controlled clinical trial of normotensive normoalbuminuric (NA) persons with T1DM.21
