Shift in location of pupil center occurs with dilation, study finds

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BOSTON — Change in the location of the center of the pupil can occur as the pupil dilates, researchers here found. These changes are generally slight but can be significant, especially when using pharmacologic agents to induce dilation, the researchers reported. The changes in the location of the pupil center are not related to refractive error, age or change in pupil diameter, according to the report. Researchers here at the Schepens Eye Research Institute and elsewhere used an infrared-sensitive camera to take high resolution images of the eyes of 70 subjects. Images were captured under mesopic, photopic and pharmacologically dilated conditions, and the centers of the pupils were computed. According to the report, the centers of the pupils showed a consistent, small temporal shift as the pupils dilated. The mean shift was 0.133 mm between mesopic and photopic conditions, as the pupils changed from 6.3 mm to 4.1 mm on average. Ninety percent of the patients had a motion of less than 0.3 mm. One patient showed motion of almost 0.6 mm. The report is published in the July issue of Investigative Ophthalmology and Visual Sciences.