To determine the relationship between tight blood pressure (BP) controland the different aspects of diabetic retinopathy in patients with type 2diabetes mellitus (DM).
Nineteen hospital-based clinics in England, Scotland, and Northern Ireland.
Outcome of retinopathy status assessed by 4-field retinal photographyrelated to allocation within a randomized controlled trial comparing a tightBP control policy aiming for a BP less than 150/85 mm Hg with a less tightBP control policy aiming for a BP less than 180/105 mm Hg.
One thousand one hundred forty-eight hypertensive patients with type2 DM were studied. These patients had type 2 DM for a mean duration of 2.6years at the inception of the Hypertension in Diabetes Study, had a mean ageof 56 years; and had a mean BP of 160/94 mm Hg. Seven hundred fifty-eightpatients were allocated to a tight BP control policy with angiotensin-convertingenzyme inhibitor or β-blockers as the main therapy; 390 were allocatedto a less tight BP control policy.
Main Outcome Measures
Deterioration of retinopathy (≥2-step change on a modified EarlyTreatment Diabetic Retinopathy Study [ETDRS] final scale), together with endpoints (photocoagulation, vitreous hemorrhage, and cataract extraction) andanalysis of specific lesions (microaneurysms, hard exudates, and cotton-woolspots). Visual acuity was assessed at 3-year intervals using ETDRS logarithmof the minimum angle of resolution charts. Blindness was monitored as an endpoint with the criterion of Snellen chart assessment at 6/60 or worse.
By 4.5 years after randomization, there was a highly significant differencein microaneurysm count with 23.3% in the tight BP control group and 33.5%in the less tight BP control group having 5 or more microaneurysms (relativerisk [RR], 0.70; P = .003). The effectcontinued to 7.5 years (RR, 0.66; P<.001). Hardexudates increased from a prevalence of 11.2% to 18.3% at 7.5 years afterrandomization with fewer lesions found in the tight BP control group (RR,0.53; P<.001). Cotton-wool spots increased inboth groups but less so in the tight BP control group which had fewer cotton-woolspots at 7.5 years (RR, 0.53; P<.001). A 2-stepor more deterioration on the ETDRS scale was significantly different at 4.5years with fewer people in the tight BP control group progressing 2 stepsor more (RR, 0.75; P = .02). Patients allocatedto tight BP control were less likely to undergo photocoagulation (RR, 0.65; P = .03). This difference was driven by a differencein photocoagulation due to maculopathy (RR, 0.58; P = .02).The cumulative incidence of the end point of blindness (Snellen visual acuity,≥6/60) in 1 eye was 18/758 for the tight BP control group compared with12/390 for less tight BP control group. These equate to absolute risks of3.1 to 4.1 per 1000 patient-years, respectively (P = .046;RR, 0.76; 99% confidence interval, 0.29-1.99). There was no detectable differencein outcome between the 2 randomized therapies of angiotensin-converting enzymeinhibition and β-blockade.
High BP is detrimental to each aspect of diabetic retinopathy; a tightBP control policy reduces the risk of clinical complications from diabeticeye disease.