Despite its popularity and safety track record, laser in situ keratomileusis (LASIK) remains associated with the rare but significant complication of corneal ectasia. One theoretical advantage of small incision lenticule extraction (SMILE), a newer refractive technique, is that it may induce less biomechanical weakening of the cornea than LASIK because it requires a much smaller anterior stromal cut,[1] ideally translating into fewer cases of postoperative ectasia.
To analyze the effect of the SMILE cap versus the LASIK flap on corneal biomechanical properties, Khamar and colleagues[2] compared results in the eyes of 24 patients before, during, and after SMILE in one eye and LASIK in the fellow eye. The creation of the SMILE cap and the LASIK flap (but before removal of the stromal tissue) both weakened the cornea, although the weakening was statistically significantly greater in the LASIK eyes.
Postoperative measurements demonstrated evidence of further weakening due to the opening of the SMILE cap and the LASIK flap interfaces and removal of the stromal tissue. However, 1 week and 1 month after surgery, the authors found similar degrees of corneal weakening compared with preoperative measurements in both SMILE and LASIK eyes. They thereby concluded that the stromal tissue removal (including opening the interface) was the primary determinant of the corneal weakening.
