Retinal blood flow after superior cervical ganglionectomy: a laser Doppler study in the cynomolgus monkey

There is a conflicting literature regarding the possible presence of adrenergic innervation of the retinal circulation. The effect of a histologically confirmed left superior cervical ganglionectomy on the total retinal blood flow in eight anaesthetised female cynomolgus monkeys was determined. Near total unilateral ocular sympathetic denervation was confirmed by ipsilateral miosis, supersensitivity of pupillary dilatation to topical phenylephrine and pupillary hyporesponsiveness to topical hydroxyamphetamine. Retinal vein diameters were measured from monochromatic photographs, maximum red cell velocities (Vmax) were measured with a helium-neon laser, using a bidirectional laser Doppler velocimeter technique, and the total retinal blood flow in each eye was determined by summation of measurements of flow in individual retinal veins. Mean (SEM) total retinal blood flow was 32.93 (1.49) and 30.41 (1.86) microliters/min in the eight sympathectomised and normal eyes respectively; the 9% (5%) difference was not statistically significant. Our study suggests that pharmacologically confirmed sympathetic denervation has little if any effect on resting total retinal blood flow.