Surgeon: Ocular alignment particularly important for wavefront-based LASIK

SAN FRANCISCO — Accurate rotational alignment of the eye is more important for correction of astigmatism using wavefront-guided LASIK than in standard surgery, according to a surgeon speaking here.

Roger F. Steinert, MD, and John Campin, MD, analyzed the impact of rotational positioning error on higher-order aberrations in 240 eyes of 169 patients undergoing treatment with Alcon’s LADARVision system. Dr. Steinert presented the results of the study here at the American Society of Cataract and Refractive Surgery meeting.

“If you are going to do wavefront measure, you are capturing the wavefront, but then you have to be able to match that wavefront to the treated eye at the time of treatment,” Dr. Steinert said. “Rotation registration does matter. Obviously, what we are trying to do is perform a wavefront ablation profile to neutralize the wavefront error of the eye at the time of treatment. If you miss a line, then you are subject to undercorrection and the induction of more aberrations.”

The study found a mean rotation of 4· (range 0· to 16·), and 28% of the eyes were rotated more than 6·.

He said there was a tendency for the left eye to rotate clockwise, while the right eye was more likely to rotate counterclockwise.

Dr. Steinert said that in the study, 66 eyes had more than 6· of rotation, and 20 eyes were rotated more than 10·, which has a significant impact.

“A 4· misalignment in and of itself, which was the average, would have resulted in a 14% undertreatment of basic astigmatism,” he said.

Dr. Steinert said rotational malpositioning has a greater negative impact on higher-order aberrations than on simple second-order astigmatism. As an example, he said, a minimium 10· rotational malposition can result in a 30% error in astigmatism correction, but a 50% error in trefoil and a 65% error in tetrafoil.

Dr. Steinert acknowledged a financial interest in the items discussed.