Defective Myogenic Response of Retinal Vessels Is Associated With Accelerated Onset of Retinopathy in Type 1 Diabetic Individuals.

PURPOSE: We seek to identify pathogenic mechanisms for diabetic retinopathy that can become therapeutic targets beyond hyperglycemia and hypertension. We investigated if a defective myogenic response of retinal arteries to increased perfusion pressure, which exposes capillaries to increased pressure and flow, is associated with the onset of clinical retinopathy.

METHODS

We examined prospectively the incidence of retinopathy in type 1 diabetic individuals tested 4 years earlier for the retinal arterial myogenic response, and in a cross-sectional study the prevalence of defective myogenic response in type 1 patients who had diabetic retinopathy. Among these, we contrasted early-onset (after 15 ± 2 years of diabetes, E-DR; n = 5) to late-onset (after 26 ± 3 years of diabetes, L-DR; n = 7) retinopathy. We measured the myogenic response using a laser Doppler blood flowmeter after a change in posture from sitting to reclining, which increases retinal perfusion pressure.

RESULTS

Five of seven participants who 4 years prior had a defective myogenic response had now developed clinical retinopathy; as compared with only one of six participants who 4 years prior had a normal response (P = 0.10). In the cross-sectional study, all participants had normal retinal hemodynamics at steady state. In response to the postural change, only the E-DR group showed defective myogenic response (P = 0.005 versus controls, P = 0.02 versus L-DR) and abnormally high retinal blood flow (P = 0.016 versus controls).

CONCLUSIONS

In type 1 diabetic patients, a defective myogenic response of retinal arteries to pressure is not required for the development of clinical retinopathy, but is prominently associated with an accelerated onset of retinopathy.