Lack of effect of short-term treatment with amlodipine and lisinopril on retinal autoregulation in normotensive patients with type 1 diabetes and mild diabetic retinopathy.

PURPOSE

Diabetic retinopathy is characterized by morphological changes in the retina secondary to disturbances in retinal blood flow. It has been shown that antihypertensive treatment has a protective effect on the development of diabetic retinopathy, and evidence suggests that inhibitors of the renin-angiotensin system have a protective effect beyond the antihypertensive effect. The background for this additional effect is unknown but might be related to an effect on retinal autoregulation.

METHODS

In a double-blinded, two-way cross-over study, 25 normotensive patients with type 1 diabetes (T1D) aged 20.6-33.9 (mean 27.9) with mild retinopathy were randomized to receive either 5 mg of the calcium channel blocker (CCB) amlodipine for 14 days followed by a washout period and treatment with 10 mg of the angiotensin converting enzyme (ACE) inhibitor lisinopril for another 14 days or the two treatments in the reverse order. Using a Dynamic Vessel Analyzer (DVA), the diameter response of retinal arterioles during an acute increase in the blood pressure induced by isometric exercise, during flicker stimulation and during both stimulus conditions simultaneously was studied before and during the two treatments periods.

RESULTS

Amlodipine and lisinopril induced a similar non-significant decrease in the arterial blood pressure. At baseline, the arterial diameter decreased by 2.4 ± 0.9% (p = 0.004) during isometric exercise, increased by 2.2 ± 0.9% (p = 0.019) during flicker stimulation and increased by 1.8 ± 0.9% (p = 0.03) during the combined stimulus conditions. Neither of the antihypertensive drugs amlodipine (p = 0.76) or lisinopril (p = 0.11) changed the diameter response of retinal vessels significantly; however, the two treatments induced a different response in the veins during combined exercise and flicker (p = 0.021).

CONCLUSIONS

Short-term treatment with amlodipine and lisinopril had no significant effect on retinal autoregulation in young normotensive patients with T1D and mild retinopathy, and this lack of effect was similar for the two drugs. A possible normalizing effect of antihypertensive treatment on retinal autoregulation was not observed; however, it might take longer time to improve autoregulation than to reduce the arterial blood pressure.