Abstract
Purpose: :
The object of this study is to determine the dynamics of the pupil light reflex response, in the presence of a surrounding glare source that flashes on and off periodically in mesopic adaptation. The influence of age was also investigated (young: 20 to 30, adults: 50 to 60), the hypothesis being that the effects would be greater for the older group. In addition, we hope to confirm the stability of the latency time for both of the group.
Methods: :
We simulated the night driving situation under laboratory conditions using periodical flashes. We recorded the changes in pupil size with the time, while the flashes occurred periodically. 20 subjects were involved in this experiment, (10 between the ages of 20 and 30 and 10 aged from 50 to 60). Those involved did not use refractive correction during testing. The task of the observers was to watch a fixation cross, without restriction of blink, while being dazzled every 5 seconds ,during 0.5 seconds, 30 times. This process was repeated 3 times, varying the background luminance: 0.1, 0.2 and 0.5 cd/m2 (mesopic range). The level of glare of measured on the iluminance of the eye was 60 lux.
Results: :
We found that after the subject was submitted to a sequence of flashes, the size of the pupil decreased, regardless of the background luminance in the range considered in this experiment. The average initial value of pupil diameter considerer for the younger group was 4,8 mm which is larger than the 3,7 mm considered for the older group. However, the proportion of this decrease is greater for the younger group (25%) than for older adults (19%). This decrease resulted in a darkening of the scene. This decreased of the pupil can be understood as a decrease in retinal iluminance, resulting in a drop of 38 % for the younger group and 29 % for the older subjets. Finally, we confirm the stability of the latency time for different values of background luminance showing no significant differences with age.
Conclusions: :
The effects of the presence of a periodic source glare in a visual field, under mesopic adaptation, produced a greater decrease in the pupil size of the younger group, producing a greater darkening effect darkening effect also increased, which does not depend on luminance adaptation in the range considered in this work. We confirm the stability of the latency time for both age groups.
Keywords: pupillary reflex • aging