Assessment of pupil size under different light intensities using the Procyon pupillometer

PURPOSE: To study the relationship between pupil size and light intensity using the Procyon pupillometer. SETTING: University based clinic. METHODS: In this retrospective study, 20 consecutive patients had pupil size assessment with the Procyon pupillometer under 3 different light conditions--4, 0.4, and 0.04 lux. Correlation was established using the log unit of the light intensity and pupil size. RESULTS: The correlation coefficient for the association between pupil size and log unit of light intensity in all eyes was significant (P<.001). The mean correlation coefficient for the association between pupil size and log unit of light intensity in all patients was 0.968 +/- 0.089 (SD) in the right eye and 0.970 +/- 0.031 in the left eye. CONCLUSION: The linear relationship between the pupil size and the log unit of the light intensity showed a tight correlation in all cases. These results can be useful in the comparing pupil size with pupillometers that work under different light conditions.