[Analysis of optic nerve head circulation in diabetics using a laser Doppler technique]

The authors measured the red blood cell speed distributions in the capillaries of the optic nerve head using a laser Doppler technique. We calculated the widths of Doppler-broadened frequency spectra of laser light scattered from temporal sites on the optic nerve head in 34 Type I diabetic patients (mean age, 29.5 years; 12 patients having no retinopathy; 22 having background retinopathy) and in 29 age- and sex-matched normal controls. Doppler broadening proportional to the red blood speed was 763 +/- 113 Hz (mean +/- SD) in the diabetics and 912 +/- 167 Hz in the controls. The difference was statistically significant. Mean blood pressure and intraocular pressure in the diabetics were not significantly different compared to controls. Our finding of abnormally low capillary blood speeds suggests that pathologic alterations occur in the microvasculature of the optic nerve head in the early stages of diabetic retinopathy.