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Dilation agents may induce unnatural pupil centroid shift, surgeon says
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CHICAGO — Use of a dilating agent before refractive surgery may cause problems with wavefront measurements, according to a surgeon speaking here.
“Pharmacologics may well interfere with the custom treatment process and shift the pupil centroid from a naturally dilated pupil,” said K. Ashley Tuan, MD, speaking here at Refractive Subspecialty Day before the American Academy of Ophthalmology meeting.
Dr. Tuan examined 32 eyes to determine the effect of medical dilation on wavefront measurement and pupil centroid. Baseline measurements were first performed on the patient’s dark-adapted pupil. Then one drop of 0.05% tropicamide was administered, and wavefront measurements were taken after 10, 20 and 30 minutes.
The average dark-adapted pupil was 6.4 mm in diameter. After administration of the tropicamide, the pupil centroid was found to have shifted with no discernable pattern, Dr. Tuan said.
“After dilation, the pupil center shifted in both the right and left eyes,” she said. “A pupil shift of more than 0.2 mm will reduce contrast sensitivity.” Up to 45% of participants had a shift of more than 0.2 mm, she said.
A diluted tropicamide formula induced less root-mean-square change in higher-order aberrations, but it also resulted in less dilation effect, she said.
“Caution should be exercised” when using medication to dilate the pupil in conjunction with wavefront measurements, Dr. Tuan advised.