Zernicke may not be enough to correct high-order aberrations, surgeon says

MUNICH, Germany — Translating data from Shack-Hartmann diagnostic readings into Zernicke polynomials for customized refractive treatment is a challenge that still needs work, according to a refractive surgeon speaking here.

The currently used algorithms “work on virgin eyes, but we need more information to accurately assess more complicated eyes,” said Douglas Koch, MD, here at the European Society of Cataract and Refractive Surgeons meeting. According to Dr. Koch, current methods for calculating Zernicke polynomials are dependent upon pupil size and do not adequately characterize sharp small features of the eye.

“Zernicke works well in normal eyes, but to try and reduce aberrations, we need a more precise algorithm,” he said. Better mathematical analysis may hold the key to the reduction of induced aberrations during laser surgery, he added.

Dr. Koch described a study in which Zernicke reconstructions were compared to reconstructions using an alternative model. The study included reconstruction of wavefronts corresponding to control plastics and 30 eyes measured with a Shack-Hartmann sensor.

In the plastic and real eyes, the accuracy of the alternative method was “almost always higher than that of the Zernicke method up to the 12th-order polynomials,” Dr. Koch said.