Customized Hinge Elliptical Versus Circular Flaps Using Femto-LASIK for Correction of Compound Myopic Astigmatism
Narrative Responses:
Purpose
To compare the refractive outcome of two flap designs using femtolaser assisted LASIK for the correction of compound myopic astigmatism.
Methods
This prospective study compared refractive outcomes in two groups of 22 eyes with compound myopic astigmatism undergoing bilateral femtolaser assisted LASIK with the FS200 femto and EX500 excimer lasers (Alcon Laboratories, Inc.). For each patient, one eye was randomized to receive a customized hinge elliptical flap (CHEF), whose longer axis and hinge were aligned with the flattest and steepest corneal meridians, respectively. The other eye was operated with a circular flap (CF). P values <0.05 were considered statistically significant.
Results
Mean preoperative myopic spherical equivalent (SE) refraction was -5.62+/-2.82 diopters (D) and -5.78+/-2.71 D for the CHE and CF groups, respectively. Mean preoperative cylinder was -1.79+/-0.91 D for the CHE and 1.85+/-0.93 D for the CF groups. Mean postoperative SE was +0.09+/-0.43 D and -0.11+/-0.62 D for the CHE and CF groups, respectively (p>0.10). Mean postoperative cylinder magnitude was 0.39+/-0.38 D and 0.24+/-0.33 D for the CF and CHE groups, respectively (P<0.02). Uncorrected visual acuity (VA) was significantly better in the CHE compared with the CF group (P<0.05).
Conclusion
An elliptical flap cut for treating compound myopic astigmatism results in better efficacy than a circular flap. This may be due to the enlargement of the stromal bed along the flat meridian, and the subsequent better matching of the available sromal zone with the characteristics of the ablation profile.