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Corneal biomechanics alteration induced by FemtoLASIK used to correct low to moderate myopia

Poster Details

First Author: M.Smorawski POLAND

Co Author(s):    J. Wierzbowska                    

Abstract Details


Corneal ectasia is uniformly linked with reduction of corneal biomechanical factors. To evaluate which of the structural surgical parameters has the primary impact on reduction of corneal biomechanics parameters measured by Ocular Response Analyzer in myopic patients who underwent FemtoLASIK.


Department of Refractive Surgery, Optegra Eye Clinic, Warsaw, Poland.


60 eyes of 60 patients undergoing FemtoLasik with the flap of 110 or 140 microns were studied prospectively. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) measurements were taken before and on days 30 and 90 after FemtoLASIK. Anterior weighted index (AWI) defined as flap thickness plus ablation depth (AD) and posterior weighted biomechanical index (PWBI) defined as residual stromal thickness (RST) to preoperative central corneal thickness (CCT) ratio were calculated. Postoperative change of CH and CRF with regard to AWI, RST, PWBI, final central corneal thickness (FCCT), CCT and AD were correlated.


OH and CRF mostly stabilized at day 30 and remained significantly unchanged till day 90. Cumulated change of CH appeared to be mostly correlated with PWBI (factor R=0.684, p<0.05) followed by FCCT (inversely related in both).Cumulated change of CRF was highly related to AD(factor R=0.589, p<0.05), followed by flap thickness (directly related in both). The flap thickness influenced measured outcomes. No statistically significant correlations were detected between CH and CRF changes and preoperative CCT.


Clinical data may suggest that alterations within anterior cornea following FemtoLASIK are the main determinants of the total corneal resistance changes. Corneal resistance changes are not dependent to preoperative CCT which might suggest that qualitative structural indices should be considered to access corneal related risks to develop postoperative ectasia. Further studies need to be conducted to compare these values with hyperopic and astigmatic treatments.

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