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Corneal stiffness changes following LASIK, SMILE and PRK refractive surgery procedures

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First Author: A.Elsheikh UK

Co Author(s):    B. Lopes   A. Eliasy   J. Wang   F. Bao   A. Abass        

Abstract Details

Purpose:

To estimate the effect of three laser vision correction surgeries on corneal material properties

Setting:

University of Liverpool Eye Hospital, Wenzhou Medical University, China.

Methods:

One-hundred fifty-six patients who underwent femtosecond laser-assisted LASIK (FS-LASIK; n=45), SMILE (n=55) or transepithelial PRK (tPRK; n=56) were retrospectively evaluated. All cases were assessed by the Corvis ST (OCULUS Optikgeräte, Wetzlar, Germany) pre and 6-month postoperatively. To exclude the influence of confounding factors, the three groups were matched for preoperative age, corrected manifest spherical equivalent (MSE), pre and postoperative central corneal thickness (CCT), biomechanically corrected intraocular pressure (bIOP), stress-strain index (SSI), stiffness parameter at the first-applanation (SP-A1) and integrated inverse radius (1/R). Differences between pre and postoperative Dynamic Corneal Response parameters (DCRs) were assessed.

Results:

The corneal overall stiffness parameters as measured by SP-A1 and 1/R were reduced in all three procedures with the tPRK presenting the lowest differences between the pre and postoperative, followed by SMILE and then FS-LASIK (p<0.05). In contrast, the corneal material stiffness, as measured by the SSI, was relatively stable before and after the procedures with 0.1±10.5% reduction after FS-LASIK (p= 0.53) and increases of 0.1±25.2% after tPRK (p= 0.79) and 6.2±12.5% after SMILE (p< 0.01).

Conclusions:

While FS-LASIK, SMILE and tPRK cause significant reductions in the cornea’s overall biomechanical stiffness, which increase with tissue separation in FS-LASIK and SMILE, these reductions are mainly due to tissue thickness loss rather than changes in the tissue’s material stiffness.

Financial Disclosure:

... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented