Pachymetry essential to safe, effective LASIK surgery

THOROFARE, N.J. — Measuring the depth of the cornea before, during and after LASIK surgery will help ensure more accurate refractive results by limiting the possibility of surgeon-induced corneal ectasia, Charles R. Moore, MD, said.

Dr. Moore suggests surgeons use ultrasonic pachymetry to determine the exact degree of flap thickness achieved and the correct amount of tissue to ablate during LASIK surgery. He recommends surgeons keep the residual stromal bed “at least 250 µm thick postoperatively.” Corneal integrity can be preserved, and surgeons can avoid iatrogenic corneal ectasia by limiting flap thickness, he added.

“The easiest way to keep the cornea at a healthy thickness is by measuring the cornea preoperatively, post-cut and again after ablation,” he said.

Current microkeratome technology cannot create flaps reproducibly or predictably with current tolerance levels around 50 µm, he said. If the surgeon does not perform intraoperative pachymetry, “a single blade can create a flap 150 µm thick one day and 250 µm thick the next day without the surgeon ever knowing,” Dr. Moore said. He added that some microkeratome companies are perfecting technology that allows for a 10-µm tolerance.

According to Dr. Moore, surgeons will not know how much tissue can be safely ablated without knowing the post-flap pachymetry.

“Depending on the overall depth of a patient’s cornea, an ideal flap may start at 65 µm or go all the way up to 180 µm,” Dr. Moore said. He has used pachymetry subtraction methods on more than 16,000 LASIK cases.

More information about Dr. Moore’s techniques and clinical studies can be found in the October 1 issue of Ocular Surgery News.