Pupil motility in long-term diabetes

Summary Employing infrared TV-videopupillography and the open loop stimulatory technique the ability of the pupil of the eye to react to rhythmic light stimuli of increasing frequencies was studied in 15 control subjects and 14 long-term juvenile diabetics. The degree of retinopathy varied from nil to proliferative changes. The visual acuity of all subjects studied was at least 6/9 and there were no ophthalmoscopic signs of retinopathy in the area stimulated by the light, thereby ensuring roughly uniform retinal sensitivity. The degree of neuropathy ranged from nil to moderate or severe as judged by vibratory perception threshold and pupil size. The pupil response (gain: fractional response to a unit light stimulus, and phase lag: latency period in number of stimulatory cycles) was the same in the group of diabetics as in the control group. The results show that the pupillary abnormalities of long-term diabetic patients (small size and a loss of spontaneous fluctuations) are probably] not due to stiffness of the iris tissues. It is suggested that diabetic autonomic neuropathy predominantly affects the sympathetic innervation to the dilator muscle, the parasympathetic innervation to the sphincter muscle being relatively spared.