Evaluation of Corneal Biomechanical Properties before and after Myopic Laser in Situ Keratomileusis

Purpose: To evaluate changes in corneal biomechanics after myopic Lasik and the correlation between corneal biomechanics and preoperative degree of refractive error, pa-chymetry and ablation depth. Methods: A 42 eyes of 23 myopic patients undergoing Lasik were evaluated using ocular response analyzer (ORA) assessing corneal biomechanics (corneal hysteresis “CH” and corneal resistance factor “CRF”) pre-Lasik, 1 month and 6 months after Lasik. Manifest refraction spherical equivalent (MRSE), central corneal thickness (CCT) and ablation depth were also recorded. Changes in corneal hysteresis (CH) and corneal resistance factor (CRF) were evaluated for correlation to pre- operative patient measurements’. Results: The preoperative mean CH and CRF (11.0± 1.0mmHg and 10.1±0.9mmHg) respectively. Significant de-crease in CH and CRF occurred at 1 month postoperatively (mean CH 9.1±1.1 and mean CRF 8.7±1.0) as well as 6 months postoperatively (mean CH 9.3±1.1 and mean CRF 8.8±0.9). The decrease in CH and CRF is strongly correlated to preop-erative manifest refraction (r=–0.86, p 0.001). The decrease is not correlated to age or preoperative CCT. Conclusions: Assessing preoperative corneal biomechanics is important in every Lasik candidate as predictable decrease in their values occur depending on manifest refraction. The characterization of corneal biomechanical properties may become a useful tool for assessing refractive surgery qualifi-cation and outcomes thus preventing corneal ectasia.