Six-month variability of the dark-adapted pupil diameter.
OBJECTIVE
To determine the individual variability of the dark-adapted pupil diameter over 6 months using a standardized dark-adaptation protocol.


METHODS
Texas Tech University Health Sciences Center, Lubbock, Texas, USA.


METHODS
This prospective observational cohort study comprised volunteers with no history of ocular disease, surgery, or injury other than requirement for refractive correction. The right eye was tested. A standardized dark-adaptation protocol was used that controlled for accommodation and patient alertness. Infrared, still digital photographs were taken after 10 minutes of dark adaptation at 1 lux and were analyzed using digital image software. Testing was performed at baseline in the afternoon, at 3 months in the afternoon, and at 6 months in the morning. Lifestyle factors such as diet and exercise were not controlled.


RESULTS
Mean intersession differences were 0.04 mm (95% confidence interval [CI]: -0.68-0.146), 0.15 mm (95% CI: -0.001-0.297), and 0.09 mm (95% CI: -0.048-0.236) for baseline-3 month, baseline-6 month, and 3 month-6 month comparisons, respectively. None of these differences was significantly different from zero (P>.05, 2-tailed Student t tests). The likelihood that the mean intersession difference was >.25 mm was negligible for all comparisons (P=.9996, .9099, and .9829 respectively, 1-tailed Student t tests).


CONCLUSIONS
When a consistent dark-adaptation protocol that controls for alertness and accommodation is used, normal young individuals showed no significant variation in the dark-adapted pupil diameter over a 6-month period.
Department of Ophthalmology, Texas Tech University Health Sciences Center, Lubbock, Texas, USA.
Arshad M
AM
Khanani
Sandra M
SM
Brown
Ke Tom
KT
Xu
D000065:Accommodation, Ocular / Q000502:physiology; D000328:Adult; D003623:Dark Adaptation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011680:Pupil / Q000502:physiology*; D013997:Time Factors