Shortcomings of wavefront technology will limit its use, surgeon says

SAN FRANCISCO — Until certain fundamental issues are resolved, wavefront customized ablation will not live up to heightened expectations, said refractive surgeon and optics expert Jack T. Holladay, MD.

Several inherent problems with the technique will for the time being prevent wavefront from becoming the laser technique of choice for most surgeons, said Dr. Holladay, here at the annual meeting of the American Society of Cataract and Refractive Surgery.

First, he said, wavefront-guided lasers have not compensated for oblique incidence of light on the cornea. The result of this is that the cornea becomes oblate, when it should be prolate, he said.

A second inherent problem he noted is that the wavefront-guided laser must be perfectly aligned or else the off-axis corrections will not work.

“When you correct lenticular aberrations on the cornea, it creates an ‘extreme’ on-axis system. (The laser) is not lined up for off-axis images,” he said.

Further, direct correction of the eye with wavefront “assumes the path through the crystalline lens is the same,” Dr. Holladay said. “Actually, the rays pass through different locations in the crystalline lens, introducing different aberrations.”

The flap created during LASIK can also induce its own series of aberrations, such as astigmatism and higher-order RMS error, he said.

Wavefront-guided correction is also limited by the characteristics of the tracking system used.

“You must have absolutely perfect fixation, which is not possible at this point,” he said.

Finally, Dr. Holladay said, contrast sensitivity should be the primary measure of visual performance, but it is impossible to gauge true contrast sensitivity after wavefront surgery because it always declines postoperatively.

“So far, custom ablation studies do not show improvement in (contrast sensitivity),” Dr. Holladay said.