Corneal Elasticity Co-Efficient Biomechanics Parameters After Laser Vision Correction Procedures

Evaluation of the changes in deformation amplitude (DA) ratio, integrated radius (IR), stress–strain index (SSI), and stiffness parameter at first applanation (SP-A1) obtained by the corneal visualization Scheimpflug technology (Corvis ST) and this is before and after different laser vision correction (LVC) procedures.

Candidates were divided into 3 groups, each of them underwent Corvis ST scan before and after different LVC procedure,
PRK, LASIK and Femto-LASIK. The study was conducted between March 2020 and Jan 2022 in DEO eye hospitals and Research
Institute of Ophthalmology, Cairo, Egypt.

An interventional study that is prospective, randomized, and comparative. Individuals having a maximum astigmatism of −3.00 D and a maximum [(mean refractive spherical equivalent (MRSE)] of −7.00 D. Using the Corvis ST, measurements were made of the DA ratio, IR, SSI, and SPA1 prior to and following three distinct LVC procedures: Photorefractive keratectomy (PRK; group I), laser assisted in situ keratomileusis (LASIK; group II), and Femto-LASIK (Femto-laser assisted in situ keratomileusis; group III).

Comparison between pre- and posttreatment showed significant increase in the DA ratio and IR with no significant change in SSI in group I. While in group II and III showed significant increase in DA ratio, IR and significant decrease in SSI. The SP-A1 change was significantly decreased in all three groups

The response of the corneal biomechanical to the three surgical procedures varied differently and the significant change was in the IR and SP-A1, where the SSI and DA ratio was nonsignificant. The results of LASIK and PRK showed the highest and lowest reductions in total corneal stiffness, respectively, while Femto-LASIK stayed in between.