Abstract
OBJECTIVE: Stimulation of the retina with flickering light increases retinal
vessel diameters in humans. Nitric oxide is a mediator of the retinal
vasodilation to flicker. The reduction of vasodilation is considered an
endothelial dysfunction. We investigated the response of retinal vessels to
flickering light in diabetic patients in different stages of diabetic
retinopathy. RESEARCH DESIGN AND METHODS: We studied 53 healthy volunteers, 68
type 1 diabetic patients, and 172 type 2 diabetic patients. The diameter of
retinal vessels was measured continuously online with the Dynamic Vessel Analyzer
(DVA). Diabetic retinopathy was classified using Early Treatment Diabetic
Retinopathy Study criteria. Changes in vasodilation are expressed as percent
change over baseline values. RESULTS: After adjustments for age, sex, and
antihypertensive treatment, the response of retinal arterioles to diffuse
luminance flicker was significantly diminished in patients with type 1 diabetes
compared with healthy volunteers. The vasodilation of retinal arterioles and
venules decreased continuously with increasing stages of diabetic retinopathy.
The retinal arterial diameter change was 3.6 +/- 2.1\% in the control group, 2.6
+/- 2.5\% in the no diabetic retinopathy group, 2.0 +/- 2.7\% in the mild
nonproliferative diabetic retinopathy (NPDR) group, 1.6 +/- 2.2\% in the moderate
NPDR group, 1.8 +/- 1.9\% in severe NPDR group, and 0.8 +/- 1.6\% in proliferative
diabetic retinopathy group. CONCLUSIONS: Flicker responses of retinal vessels are
abnormally reduced in diabetic patients. This decreased response deteriorated
with increasing stages of retinopathy. The response was already reduced before
clinical appearance of retinopathy. The noninvasive testing of retinal
autoregulation with DVA might prove to be of value in early detection of diabetic
vessel pathological changes.
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