The effect of cervical sympathectomy on retinal vessel responses to systemic autonomic stimulation

The retinal vessel calibre responses to systemic sympathetic stimulation, were studied in nine patients (eight male; mean age: 31.7 years; range: 19-58 years) with unilateral disruption of their cervical sympathetic tract. All patients had ipsilateral decreased/absent facial sweating and a Horners syndrome, evidence of unilateral sympathetic denervation. Both eyes of each patient were studied and the results were analysed in two groups: the group of nine sympathectomised eyes and the control group of unaffected fellow eyes. During handgrip contraction there was a significant difference in the mean retinal arteriolar constriction (mean +/- SEM) between the group of sympathectomised eyes (4.6 +/- 0.89%) and control eyes (7.1 +/- 1.13%), p less than 0.01. Similarly, there was a significant difference in mean venule constriction during sustained handgrip contraction between the group of sympathectomised eyes (1.5 +/- 0.67%) and control eyes (4.9 +/- 0.98%), p less than 0.05. There was no significant difference in the mean rise in diastolic blood pressure between the two groups: control eyes +27.9 +/- 2.38 mmHg and sympathectomised eyes +27.8 +/- 2.25 mmHg. There was no correlation between the blood pressure and retinal vessel responses in either group. These results suggest that the sympathetic nervous system plays an integral role in retinal blood flow regulation.