Abstract:Background: The emergence of CorVis ST as a non-invasive method enables in vivo studying of the corneal biomechanical properties as the cornea is inevitably altered biomechanically following any kind of refractive surgery including SMILE. While many research has investigated as well as compared the corneal biomechanical response following SMILE as opposed to other laser refractive procedures utilizing flaps, few research have specifically focused on the corneal cap thickness’s effect on postoperative biomechanical strength.
Objective: To compare the impact of applying different cap thicknesses (100 µm & 120 µm) on the corneal biomechanical properties following (SMILE) while management of mild to moderate myopia.
Patients and Methods: A prospective, comparative, interventional, randomized study was conducted on 40 eyes (of 20 cases) with mild to moderate myopia with or without astigmatism. They went through an equal and random categorization into two groups underwent SMILE where group A operated with 100 µm and group B operated with 120 µm cap thickness. They were compared pre- and 3 months postoperatively regarding visual outcomes, topographical outcomes using Pentacam, and biomechanical outcomes as evaluated by CorVis ST.
Results: A statistically significant difference was documented among both groups as regard the deformation amplitude ratio (DA ratio). Moreover, a negative statistical correlation between the preoperative central corneal thickness (CCT) and postoperative corneal biomechanical index (CBI) was demonstrated. Nevertheless, no statistically significant variations were documented regarding other corneal biomechanical parameters, topographic parameters, or the visual outcomes.
Conclusion: Three months after the surgery, corneal biomechanics-deformation amplitude in particular- were marginally less altered in group A operated with a 100 µm cap thickness (thinner cap) in comparison with group B operated with 120 µm (thicker cap). Both groups exhibited similar visual and topographical outcomes.
