Pupil center shift relative to the coaxially sighted corneal light reflex under natural and pharmacologically dilated conditions

PURPOSE: To evaluate the location and shift of the pupil center relative to the coaxially sighted corneal reflex on horizontal and vertical planes under natural and pharmacologically dilated conditions. METHODS: Ninety-four (64 myopic and 30 hyperopic) eyes of 47 patients underwent pupillometry with the NIDEK OPD-Scan under photopic and mesopic conditions before and after instillation of cyclopentolate 1%. Horizontal, vertical, and vectorial shift of the pupil center were calculated between each condition. RESULTS: The pupil center was located temporally to the coaxially sighted corneal reflex a mean distance of 0.336 +/- 0.181, 0.345 +/- 0.195, and 0.339 +/- 0.170 mm under photopic, mesopic, and pharmacologically dilated conditions, respectively. The pupil center shifted primarily inferotemporally (44%), followed by inferonasally (22%), superotemporally (19%), and superonasally (15%) from photopic to pharmacologic dilation. Mean magnitude of pupil shift was 0.084 +/- 0.069 mm (range: 0.010 to 0.385 mm) from mesopic to photopic, 0.149 +/- 0.080 mm (range: 0.013 to 0.384 mm) from photopic to pharmacologic dilation, and 0.102 +/- 0.104 mm (range: 0 to 0.530 mm) from mesopic to pharmacologic dilation. Mean distance between the pupil center and the coaxially sighted corneal reflex was greater in hyperopes than in myopes (P < .05), but no significant difference was observed in pupil center shifts between myopes and hyperopes under all three conditions (P > .05). CONCLUSIONS: The pupil center is located temporally and shifts in every direction, primarily inferotemporally, relative to the coaxially sighted corneal reflex with natural and pharmacologic dilation. The horizontal distance between the pupil center and the coaxially sighted corneal reflex was significantly higher in hyperopes than in myopes.