LASIK flap creation methods yield insignificant posterior corneal elevation changes

J Refract Surg. 2011;27(4):261-268.

LASIK with three different flap creation modalities resulted in insignificant posterior corneal elevation changes at 18 months postop, a study found.

"Measuring accurate corneal posterior elevation is crucial for predicting risk of keratectasia," the study authors said. "Several studies have evaluated posterior corneal changes after refractive surgery in an effort to predict response of the cornea to ablation."

The prospective study included 90 eyes of 90 myopic patients who underwent LASIK. Thirty patients underwent flap creation with the IntraLase FS60 femtosecond laser (Abbott Medical Optics), 30 with the Amadeus mechanical microkeratome (Ziemer) and 30 with LASEK using 20% alcohol.

Mean patient age was 24.8 years in the femtosecond flap group, 26.2 years in the microkeratome group and 26.3 years in the LASEK group.

Patients underwent imaging of the posterior corneal surface with the Pentacam Scheimpflug camera (Oculus) preoperatively and at 18 months postoperatively. Changes in posterior corneal elevation were measured at 21 points in the central 5-mm area of the cornea, along the vertical and horizontal meridians.

Study results showed that the mean change in posterior corneal elevation was 5.13 µm in the femtosecond flap group, 5.78 µm in the microkeratome group and 6.68 µm in the LASEK group. Between-group differences were statistically insignificant.

Changes in posterior corneal elevation were insignificant within each group.

Correlations between ablation depth, residual bed thickness and change in posterior corneal elevation were insignificant, the authors reported.