[Age changes in pupillary light reflex. A demonstration by means of a pupillometer]

A new binocular infrared video-pupillograph (C-2515, Hamamatsu Photonics) with a solid state vidicon tube was developed. Various pupil parameters were instantaneously analyzed by a built-in computer system. The equipment also enabled storage of the data on diskettes. A light reflex, induced by a photic stimulus with a duration of 250 msec (intensity: 3,000 troland) was studied. Several parameters of the light reflex were analyzed. These were: pupil area, change in the area of light stimulus, rate of constriction, latency time, and dilatation time at 63% of the amplitude. A total of 160 subjects (320 eyes) was studied. The ages ranged from 5 to 84 years, and subjects were placed in appropriate ten-year age groups (e.g., 0-9 years, 10-19, 20-29, 30-39, etc.). Ten males and 10 females were included in each group. The light reflex was studied in both eyes. The pupil area reduced as the age advanced, with negative correlation. The pupil area in females over 50 years showed a steeper reduction in size, possibly due to hormonal influences. The latency time at 20 years old was the shortest. In subjects below 10 and over 60 years, the latency time was significantly prolonged when compared with the other age groups. The ratio of the velocity of constriction against the velocity of dilatation was calculated and a negative correlation was seen. This may indicate that there are sympathetic influences related to aging and pupil dynamics. The results revealed that an examination of the light reflex by this new pupillography expressed the precise influence of aging on the pupil.