Corneal Flap Thickness Accuracy And Predictability After Femtosecond (Zeimer) LASIK And Sub-Bowman`s Keratomileusis

1. Rajiv Mirchia
2. Sahil Pahwa
3. Kanish Mirchia
4. Monica Jain
5. Avnish Gupta
6. Vikrant Sharma

Purpose: To compare the accuracy and predictability of corneal flap thickness after femtosecond ( Zeimer) LASIK (Z-LASIK) Vs. Sub-Bowman`s Keratomileusis (SBK).

Methods: Ten patients undergoing LASIK were selected for each group i.e. twenty eyes of ten patients undergoing Z-LASIK (femtosecond by ZEIMER machine for flap making and EXCIMER by NIDEK) and twenty eyes undergoing SBK (MORIA Keratome for flap making and EXCIMER by NIDEK). Pre-LASIK and post-LASIK corneal thickness was measured using PENTACAM-HR and OPTOVUE anterior segment OCT. Post-LASIK flap thickness was measured on post-LASIK day one using anterior segment OCT. Difference between planned(preset) flap thickness and achieved flap thickness, marked as variation was calculated and analyzed statistically.

Results: Both the procedures yielded appreciable results post-LASIK in terms of Visual Acuity and patient comfort. The average variation measured in case of Z-LASIK in twenty eyes was 1.075 microns while in SBK it was 4.875 microns. The maximum variation from the preset flap thickness in Z-LASIK was ± 6 microns i.e. 6 microns thicker than planned and 6 microns thinner than planned, while in SBK it was ± 19 microns.

Conclusion: It was concluded that both the procedures produced comparable results in terms of visual acuity and patient comfort but the accuracy of flap thickness produced with Z-LASIK was far better than as with SBK. Hence a refractive surgeon can be more certain regarding the predictability of flap thickness with Z-LASIK as compared to SBK and this provides better comfort level in patients with higher refractive errors and thinner corneas.