Outcomes Of Laser-Assisted In Situ Keratomileusis In Myopic Patients With Very Thick Corneas: A Retrospective Cohort Study

To evaluate the safety, efficacy, and refractive outcomes of laser-assisted in situ keratomileusis (LASIK) in myopic patients with very thick corneas (greater than 600 microns) compared to those with normal corneal thickness (between 500 and 600 microns). Although concerns exist regarding performing LASIK on patients with very thick corneas, this study investigates whether these individuals achieve comparable results in uncorrected and corrected distance visual acuity, refractive stability, safety, retreatment rates and postoperative ectasia.

A retrospective analysis of LASIK procedures performed at Care-Vision Laser Centers, a high-volume refractive surgery clinic in Tel Aviv, Israel, between January 2010 and June 2024.

A total of 27,729 eyes from patients 20 - 40 years of age with myopia up to -12.0 diopters were included. Eyes were divided into two groups based on corneal thickness: the normal corneal thickness group, (26,761 eyes) with corneal thickness of 500 - 600 microns, and the very thick cornea group, consisting of 968 eyes with corneal thickness >600 microns. Preoperative, intraoperative, and postoperative parameters were analyzed, including uncorrected and corrected distance visual acuity, refraction, corneal curvature, optical zone, maximum ablation depth, percent of corneal tissue ablated, residual stromal bed thickness, and retreatment and ectasia rates. Statistical adjustments were made to account for potential confounding variables.

Following LASIK, there were no significant differences in uncorrected distance visual acuity (0.987 versus 0.986, p=0.294), corrected distance visual acuity (0.991 versus 0.989, p=0.123), or spherical equivalent refraction (-0.024 versus -0.033 diopters, p=0.973). Safety index (1.030 versus 1.025, p=0.169) and the efficacy index (1.025 versus 1.022, p=0.379), were also comparable between the two groups. Retreatment rates remained similarly low, at 0.30 percent in the normal corneal thickness group and 0.31 percent in the very thick cornea group (p=0.301). No cases of corneal ectasia were observed in either group during the follow-up period, which averaged over nine months in both groups.

LASIK in myopic patients with very thick corneas is as safe and effective as in those with normal corneal thickness. Despite existing concerns regarding the potential risks of performing LASIK on patients with very thick corneas, this large-scale analysis found no increased risk of adverse outcomes, including loss of best-corrected visual acuity, need for retreatment, or development of corneal ectasia. These findings support broadening the eligibility criteria for laser-assisted in situ keratomileusis in patients with very thick corneas, providing strong evidence that they can safely undergo the procedure with outcomes comparable to those with normal corneal thickness.