Study finds flap-induced aberrations may return to baseline after 1 month

SAN FRANCISCO — Changes in higher-order aberrations following creation of the LASIK flap appear to be transitory and may return to almost preoperative levels, a prospective study found.

In an attempt to determine what aberrations are induced by LASIK flap creation, Ronald Krueger, MD, studied 26 eyes that underwent a two-step LASIK procedure. Aberrations were measured preoperatively, after the flap was made, and at 1 day, 1 week and 1 month. Patients were also followed up at 1 week and 3 months after surgery, he told attendees here at the annual meeting of the American Society of Cataract and Refractive Surgery.

In the procedure, Dr. Krueger waited 1 month after the flap was created before performing the laser portion of the surgery. Two microkeratomes were used on each patient. A flap was created in one eye using the Moria M2 microkeratome; the flap in the second eye was made using Alcon’s SKBM. Also, one eye of each patient was treated with standard LASIK, while the second eye received a wavefront-based LASIK procedure.

Results indicated there was a slight hyperopic shift in the manifest refraction and the wavefront refraction after the flap was created. Higher-order aberrations also changed, particularly coma and coma axis, which Dr. Krueger said correlated to hinge placement.

Dr. Krueger said the mean coma was fairly consistent among eyes, with no significant difference between eyes following flap creation. However, once the eyes were treated with either the standard or wavefront-enhanced LASIK, a significant increase in coma and spherical aberration was seen.

Dr. Krueger said the changes in coma tended to return to the preoperative levels 1 month after flap creation. Spherical aberration tended to remain elevated postoperatively.

"Really, we can’t yet predict flap-induced higher-order aberrations," Dr. Krueger said.