The Problem of Cyclotorsion in the Correction of Myopia and Myopic Astigmatism by the SMILE Method

For the treatment of myopia and myopic astigmatism, the most commonly performed laser refractive surgical technique is Laser in situ keratomileusis (LASIK). In recent years, minimally invasive lenticule extraction (SMILE) has emerged as a promising alternative to LASIK, requiring only a femtosecond laser to create the intrastromal lenticule. LASIK and SMILE have comparable visual outcomes in terms of safety, efficacy, and predictability. SMILE has been shown its result in less severe postoperative dry eye symptoms and faster corneal sensitivity recovery than LASIK. However, several authors have noted a clear trend toward undercorrection in SMILE, which is more pronounced in cases where preoperative astigmatism is greater. Astigmatism correction with femto-LASIK is more advantageous than with SMILE. The reason for this is cyclotorsion, which is not controlled when using the VisuMax platform. Cyclotorsia is a common problem when correcting astigmatism, as a cyclotorsional error of just a few degrees is a source of astigmatic undercorrection. Although dynamic cyclotorsion should not be a problem when performing SMILE due to the fixation of the eyes during laser treatment, static cyclotorsion must be compensated for, as proper axis alignment and pupillary centration are critical to achieving refractive results.