Measurement of pupil size with the video screen of an infrared autorefractor

Pupil Size in Refractive Surgery Candidates

PURPOSE

To assess pupil size measurements obtained under scotopic and mesopic conditions with the Procyon pupillometer and under photopic conditions with the Humphrey videokeratographer.

METHODS

The pupil sizes of 96 candidates for refractive surgery (192 eyes) were measured with the Procyon pupillometer PS2000 SA and the Humphrey Atlas 992 corneal topographer. Anisocoria and pupillary unrest were analyzed according to gender (two groups: 51 females and 45 males), age (five groups: 20 to 30 yr, 31 to 40 yr, 41 to 50 yr, 51 to 60 yr, older than 60 yr) and level of refraction (five groups: >-6.00 D SE, -6.00 to -3.00 D SE, -3.00 to 0 D SE, 0 to +2.50 D SE, +2.50 to +5.00 D SE).

RESULTS

The median value of pupil diameter measured with the Procyon pupillometer at the scotopic (0.04 lux), mesopic-low (0.4 lux), and mesopic-high (4 lux) levels of illumination were 6.54+/-0.88 mm; 5.62+/-0.95 mm, and 4.09+/-0.76 mm, respectively. The median pupil size with the Humphrey topographer was 3.65+/-0.62 mm. Pupillary unrest was highest at the mesopic-high level of illumination, with a median value of 0.31+/-0.34 mm. Median pupil size measured with both instruments at all light levels dropped significantly after the fifth decade of life (P<.05, ANOVA).

CONCLUSIONS

The Procyon pupillometer and Humphrey videokeratographer revealed an inverse correlation between the pupil size and the age, but no relationship with gender or level of refraction. The Procyon pupillometer provides an objective method for measuring pupil size at controlled light levels with a permanent printed record.

Day to day variability of the dark-adapted pupil diameter

PURPOSE

To determine the individual variability of the dark-adapted pupil diameter over 2 testing sessions using a standardized dark-adaptation protocol.

SETTING

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

METHODS

In this prospective observational cohort study, 40 volunteers with no history of ocular disease, surgery, or injury other than requirement for refractive correction were included. 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 5 and 10 minutes of dark adaptation and analyzed independently by 2 investigators using digital-image software. Two test sessions were performed 1 to 7 days apart. Lifestyle factors such as sleep, diet, and exercise were not controlled.

RESULTS

The mean subject age was 31.5 years (range 20 to 49 years). There were 20 men; 27 subjects wore correction for myopia, and 13 wore no correction. The mean interval between test sessions was 2 days (range 1 to 7 days). The mean difference and 95% confidence intervals for pupil diameter difference between sessions were as follows: 5-minute readings, +0.032 mm (-0.030 to +0.094); 10-minute readings, -0.006 mm (-0.059 to +0.047); mean of 5- and 10-minute readings, +0.013 mm (-0.038 to +0.064). Using the paired t test, the pupil diameter did not differ significantly between sessions in 5-minute dark adaptation (P =.2980), 10-minute dark adaptation (P =.8263), or the mean (P =.6049).

CONCLUSION

Using a consistent dark-adaptation protocol that controlled for alertness, individuals aged 20 to 49 years showed no significant variation in dark-adapted pupil diameter when tested twice in 1 week.