CHANGES IN AUTONOMIC FUNCTION WITH AGE - A STUDY OF PUPILLARY KINETICS IN HEALTHY-YOUNG AND OLD-PEOPLE

The object of the study was to compare rearing pupil diameter in darkn ess and light, and the pupillary darkness and light reflexes between a group of young and elderly healthy subjects. Twelve young (eight men, four women; median age 19.5 years) and 14 elderly subjects (six men, eight women; median age 69 years) participated. Pupil diameter was mon itored with an infra-red television pupillometer. Resting pupil size w as measured in light (16 and 32 Cd m(-2)) and in darkness. The darknes s reflex was elicited by switching off the ambient illumination (16 Cd m(-2)) for 1 s. The light reflex was elicited in darkness by short (2 00 ms) pulses of green (peak wavelength 565 nm) light at four ascendin g stimulus intensities (8.5 x 10(-3), 7.0 x 10(-2), 0.43 and 1.84 mW c m(-2)). The amplitude (mm) and maximum velocity (mm s(-1)) of the dark ness reflex and the latency (ms), amplitude (mm), maximum constriction velocity (mm s(-1)) and 75% recovery time (s) of the light reflex wer e measured. The resting pupil diameter was found to be smaller in the elderly group at all three illumination levels (p = 0.001). The amplit ude and maximum dilatation velocity of the darkness reflex were smalle r for the elderly group (p = 0.001). The amplitude of the light reflex at the three highest light intensities and maximum constriction veloc ity at all light intensities were smaller in the elderly group (p = 0. 002). Seventy-five per cent recovery time was longer in the elderly gr oup (p = 0.02). There was no difference in the latency of the light re flex response between the two groups. The reduced pupil size, diminish ed darkness reflex amplitude and velocity, and prolonged recovery time of light reflex are consistent with sympathetic deficit in old age. A lthough the reductions in light reflex amplitude and constriction velo city in the elderly group at first sight would indicate a parasympathe tic deficit in old age, they are more likely to be secondary to the gr ossly diminished pupil size.