Purpose:
To study autoregulation of retinal arterioles in type 2 diabetic patients with mild diabetic retinopathy at baseline, and after 2 and 5 years to correlate changes in autoregulation with changes in retinopathy.
Methods:
Sixty-five type 2 diabetic patients (mean age 57.2y, range: 43,9y - 65.3y) were examined. All patients had mild (1 to 4 dot and blots haemorrhages alone) in at least one eye, had no other known systemic vascular or eye disease, and none had been treated with retinal photocoagulation. All patients underwent a general ophthalmological examination including measurement of visual acuity, intraocular pressure, slit lamp examination, and funduscopy. Subsequently, the Retinal Vessel Analyzer was used to measure the diameter response of a retinal arteriole within 2 disc diameters from the optic disc at rest as well as during isometric exercise when a hand weight of 2 kg was held out from the body with the right arm. During the RVA examination the systemic blood pressure was measured on the upper left arm at rest and during exercise.
Results:
The range of the visual acuity of the examined eye was from 0.6 to 1.2 and with a mean of 0.97.The results from the baseline examination are given in table 1Exercise induced a significant change in MAP (p<0.0001), and a non-significant dilatation of the retinal arterioles (p=0.79). A considerable variation was observed in the diameter response among the patients (Variance = 9.6), however no significant correlation was found between the change in diameter and the change in MAP (p=0.18).
Conclusions:
Type 2 diabetic patients with mild diabetic retinopathy have a diminished autoregulatory response in the retinal vessels, which is in contrast to previous studies of healthy subjects where a contraction was found. Follow-up examination of the cohort to observe whether a further development of diabetic retinopathy is paralleled in changes in autoregulation will indicate whether these two parameters are related causally.
Keywords: diabetic retinopathy • blood supply • diabetes