Long-term Safety And Efficacy Of Laser In Situ Keratomileusis In Eyes With Thin Corneas

Objective:To investigate the long term(? 5 years)corneal biomechanical state,safety,efficacy and accuracy of laser in situ keratomileusis(LASIK)in eyes with thin corneas(central corneal thickness(CCT)<500 ?m).Methods:One-hundred and seventy five eyes of 89 patients who had thin corneas and underwent LASIK ? 5 years ago were included.Preoperative parameters recorded included uncorrected visual acuity(UCVA),corrected distance visual acuity(CDVA),manifest refraction,and CCT.At returning visits,in addition to visual acuity and manifest refraction,ultrasound CCT and corneal topography were performed.Optical coherence tomography was used to measure the CCT,LASIK flap thickness,and residual stromal bed thickness(RSBT).Safety index,efficacy index,percentage of eyes within ± 0.5 D and ± 1.0 D of refraction,percent tissue altered(PTA),and percentage stromal bed thickness(PSBT)were calculated.Results:The safety index was 1.09 and efficacy index was 0.99.The percentages of eyes within ± 0.5 D and ± 1.0 D were 71.2% and 87.7%,respectively.The mean PTA was(40% ± 6%)(range 20% to 55%).The mean PSBT was 61% ± 9%(range 51% to85%).No eyes developed ectasia.Conclusion:In this cohort with the PSBT of 50% or more,cornea biomechanical state was stable and LASIK was safe with follow-up for at least 60 months.