Influence Of Flap Thickness On Posterior Corneal Elevation After LASIK Performed With Femtosecond Laser

1. Choun-Ki Joo¹
2. Chang-Rae Rho¹
3. Kyung-Jin Cho¹
4. Yong-Soo Byun¹
5. Ho-Sik Hwang¹

¹Department of Ophthalmology and Visual Science, Seoul St. Mary's Hospital

Purpose
To evaluate and compare posterior corneal changes using elevation data obtained from Pentacam (Oculus) Scheimpflug imaging in eyes undergoing LASIK with two different thikckness of flap creation: 90 μm, 110 μm

Methods
Patients undergoing myopic refractive surgery were recruited. The change in posterior corneal elevation at 21 predetermined points in the central 5-mm area was measured using exported elevation data from the Pentacam before LASIK and 3 months postoperative and was compared among and within two different thickness of flap creation.

Results &Conclusions
Forty-two eyes of 38 patients were analyzed. The flap thickness 90 μm was twenty eyes and the flap thickness 110 μm was twenty-two eyes. Mean change in posterior elevation in the central 5-mm area was 5.13±4.16 μm for the 90 μm group, 5.78±4.42 μm for the 110 μm group (P=.59). Change in posterior elevation before and after LASIK was not significant within any group (P=.342, P=.232, for the 90 μm, and 110 μm groups, respectively).
Preoperative spherical equivalent, central corneal thickness, ablation depth, and estimated residual bed thickness did not correlate with change in posterior corneal elevation for the 90 μm group and 110 μm group (P=.05).
Using Pentacam elevation data, there were no significant changes in posterior corneal elevation following LASIK between or within the two thickness of flap creation. At 3 months after LASIK, the posterior corneal surface is not displaced anteriorly significantly and is equally stable using these two different flap thickness.