The blood pressure-induced diameter response of retinal arterioles decreases with increasing diabetic maculopathy

The aim of the study was to compare the diameter response of retinal arterioles and retinal thickness in patients with different stages of diabetic maculopathy during an increase in the arterial blood pressure.

Four groups each consisting of 19 individuals were studied. Group A consisted of normal individuals and groups B-D consisted of type 2 diabetic patients matched for diabetes duration, age, and gender, and characterized by: Group B no retinopathy, Group C mild retinopathy, Group D maculopathy not requiring laser treatment. The diameter changes of a large retinal arteriole were measured using the Retinal Vessel Analyzer (RVA, Imedos, Germany) before, during, and after an increase in the blood pressure induced by isometric exercise. Additionally, the retinal thickness was measured using optical coherence tomography scanning.

The arterioles contracted during isometric exercise in normal persons (diameter response: -0.70+/-0.48%) and in patients with no retinopathy (-1.15+/-0.44%), but dilated in patients with mild retinopathy (0.41+/-0.49%) and diabetic maculopathy (0.54+/-0.44%), p=0.01. Retinal thickness was normal in Group A (260+/-5.0 microm), Group B (257+/-4.5 microm), and Group C (253+/-4.4 microm), but was significantly (p=0.006) increased in Group D (279+/-5.3 microm).

The diameter response was reduced in type 2 diabetic patients with retinopathy, whereas retinal thickness was increased in patients with diabetic maculopathy. This suggests that impairment of diameter response in retinal arterioles precedes the development of diabetic macular edema.