Effect of Mesopic/Scotopic Luminance on Pupil Diameter and Anisocoria in Drivers Over 65 Years of Age

Abstract

Purpose: To evaluate the changes produced in pupil diameter and anisocoria in mesopic and scotopic conditions in subjects over the age of 65 years. Methods: A prospective evaluation was performed of pupil diameter in 45 motor car drivers aged 65 to 80 years (69±6 years). Measurements were made using an infrared, binocular pupillometer P2000 (Procyon Instruments Ltd) at 3 luminance levels: 0.04 lux (scotopic), 0.4 lux (low mesopic) and 4 lux (high mesopic). For each measurement, 10 photographs of both eyes are automatically taken by the instrument. Results: In scotopic conditions, mean pupil sizes were RE 5.37±1.1 mm, LE 5.29±1 mm. When the luminance level was increased to 0.4 lux (low mesopic conditions) mioses of 18% and 17%, respectively for the right and left eyes, were observed, resulting in pupil diameters of RE 4.55±0.83 mm, LE 4.51±0.78 mm. In high mesopic conditions (4 lux), pupil diameters were RE 3.47±0.60 mm, LE 3.41±0.89 mm, corresponding to mioses from the previous luminance level of 28% and 29%, respectively. The diferences in pupil diameter among the three luminance levels were significant. No diferences attributable to the luminance level were detected between each eye. The degrees of anisocoria observed were 5.77%, 5.78% and 5.77% in scotopic, low and high mesopic conditions, respectively. No significant diferences in scotopic/mesopic pupil sizes were revealed when the population was divided into three (15–year) age groups, or according to sex. Conclusions: At scotopic and mesopic luminance levels, drivers over 65 years show significant diferences in pupil diameter but no changes in anisocoria.