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Pharmaceutical dilation not ideal for wavefront
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SAN DIEGO – The use of pharmaceutical dilation may interfere with wavefront measurements and should be used with caution, according to a study presented here Friday at the American Academy of Optometry meeting.
The study, presented by Ashley Kuang-Mon Tuan, OD, stressed the importance of pupil size in wavefront measurement for refractive surgery. “Wavefront-guided treatment depends on a large enough pupil,” Dr. Tuan said.
The study addressed this need by assessing the impact of pharmaceutical dilating agents on wavefront measurements. Dr. Tuan looked at 32 eyes, with all subjects returning for subsequent procedures. These patients had a mean refractive error of –2.19 D +/-3.46 D (4.5 D to –10.88 D) and average age of 40 +/- 12 years (20 to 59). The Visx WaveScan System was used to collect a baseline measurement with the patient’s natural dark-adapted pupil. Each eye was then administered a 0.05% drop of tropicamide, and wavefront measurements were performed at 10, 20 and 30 minutes. After these measurements, one drop each of 0.5% tropicamide and 2.5% phenylephrine were administered, and wavefront measurements were taken again 30 minutes after the last eye drop.
The study found that after being dilated with pharmaceutical agents, the pupil centers had shifted in a non-systematic pattern, compared to the naturally dilated (dark-adapted) pupils. A pupil-center shift of 0.2 mm or more was found in up to 45% of the study population. The study found that changes in higher-order aberrations were induced in up to 18% of the population.
“If we choose to dilate regularly, 45% of the population will not get the full benefit of wavefront,” Dr. Tuan said. “Caution should be applied.”
The study advised against the regular use of pharmaceutical dilation in wavefront sensing.