Long-Term Results of Laser In Situ Keratomileusis in Myopic Patients with Topographic Indices Outside Suggested Ranges

Introduction: To investigate the long-term results of laser in situ keratomileusis (LASIK) in patients with one or more topographic indices outside the suggested range preoperatively.

Methods: Patients who had conventional or femtosecond laser-assisted LASIK for myopia correction between 2011 and 2015, and had at least one preoperative corneal topographic index outside the suggested range were contacted for a follow-up examination. Ranges were based on the cutoffs suggested for subclinical keratoconus: thinnest pachymetry (TP) < 497.50 µm, maximum keratometry (Kmax) > 47.20 D, maximum 8 mm best-fit-sphere anterior elevation (MaxAE) > 9.50 µm, maximum 8 mm best-fit-sphere posterior elevation (MaxPE) > 20.50 µm, and Belin/Ambrósio enhanced ectasia display-total deviation (BAD-D) > 1.60.

Results: Two hundred thirty patients (377 eyes) were enrolled; their mean age at baseline and at follow-up was 30.78 ± 8.16 and 9.06 ± 1.91 years, respectively. Mean ± SD was 484.36 ± 11.49 for TP (n = 133), 48.17 ± 0.83 for Kmax (n = 133), 16.33 ± 5.39 for MaxAE (n = 35), 27.87 ± 7.86 for MaxPE (n = 34), and 1.97 ± 0.36 for BAD-D (n = 162). Post-LASIK and suspected ectasia was found in one (0.26%) and two (0.53%) eyes, respectively. In the remaining 374, the efficacy and safety indices were 0.96 ± 0.14 and 1.01 ± 0.08, respectively. Uncorrected distance visual acuity (UDVA) was not reduced in any eyes, and corrected distance visual acuity (CDVA) was reduced one line in 1.9% of the cases; 79.9% of the cases were emmetropic. The long-term changes in UDVA, CDVA, and spherical equivalent were not different between groups with one, two, or three out-of-range topographic indices (all P > 0.05).

Conclusion: A single out-of-range topographic index is not a strong predictor for postoperative complications, and one should consider the combination of topographic and clinical findings, or the pattern they create in tandem. Developing a scoring system that would take a combination of indices and topographic patterns may help improve the predictive accuracy of these indices.