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G. Weigert, B. Pemp, G. Garhofer, K. Karl, U. Petzl, M. Wolzt, L. Schmetterer; Nitroglycerin-Mediated Retinal Vasodilatation Is Maintained in Patients With Diabetes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2088.
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A variety of studies indicate that patients with diabetes show abnormal retinal autoregulation. The mechanism behind this reduced capacity of retinal vessels to adapt to changes in perfusion pressure remains, however, largely unclear. One possibility is that diabetic retinal blood vessels show a generally reduced vasodilator and/or vasoconstrictor capacity due to the morphological changes associated with the disease. To test this hypothesis we compared the response of retinal arteries to systemic nitroglycerine in patients with diabetes and healthy controls.
In the present study 20 patients with insulin dependent diabetes, no or mild non-proliferative diabetic retinopathy, and serum cholesterol levels < 250 mg/dl were included. In addition, 20 healthy age-matched controls were studied. Retinal vessel diameters and systemic blood pressures were studied before and immediately after a single sublingual dose of 0.8 mg of nitroglycerin. Retinal vessel diameters were measured continuously using the Imedos Retinal Vessel Analyzer. The retinal vessel response between the two groups was compared by using an unpaired t-test.
The vasodilatory response of retinal arterial diameter to nitroglycerin was 1.64% ± 0.78% in patients with diabetes and 1.67% ± 0.78% in healthy control subjects. Likewise, the retinal venous vasodilatory response was 1.57% ± 0.71% in patients with diabetes and 1.67% ± 0.66% in healthy control subjects. Neither the nitroglycerine-induced vasodilatation in retinal arteries nor in retinal veins was different between the two groups. Systemic blood pressure was reduced in both groups after systemic nitroglycerin, but to a comparable degree.
The present study indicates that in patents with diabetes with no or mild non-proliferative diabetic retinopathy the retinal vessel response to a direct nitro-vasodilator is maintained. This indicates that abnormal retinal autoregulation, as observed previously, is not the consequence of a generally reduced retinal vascular reactivity of retinal vessels in this disease.
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