Abstract
Purpose: The aim was to report on the visual outcomes and safety of myopic LASIK performed in patients with corneas of central thickness below average(<540μm) and normal topography. Methods: This is a retrospective cohort study conducted at a private practice setting on Mexican Hispanic patients who underwent myopic LASIK between January 2014 and January 2015. An analysis of records of patients >18 years-old with previous normal topography, stable refraction, corrected visual acuity ≥ 20/20 (Snellen), Central Corneal Thickness (CCT) < 540μm and at least 12 months follow up after surgery was conducted. The main outcome measures were standard visual outcomes (efficacy, safety, refractive stability) and Percent Tissue Altered (PTA) analysis was conducted. Results: A total of 51 patients (102 eyes) were included; 56% (n=57) were female. The mean age was 26.52 ± 8.06 (range 18-55 years) with a mean follow up of 13.9 ± 1.2 months. Preoperative CCT was 515.44 ± 17.87μm (range 452- 540μm), with a mean refractive spherical equivalent (SEQ): -4.08 ± 2.17 D (range -0.75 to -9.75 D), and mean refractive cylinder: -1.44 ± 1.29 D (range 0.00 to -6.00 D). Mean predictability of postoperative SEQ was -0.20 ± 0.40 D (range -1.25 to +1.25). Postoperative SEQ was ±0.50 D in 71%, ±1.00 D in 93% of the eyes. Postoperative uncorrected distance visual acuity was ≥20/20 in 78% and ≥20/25 in 95%. One line of CDVA was lost in 3% of the eyes, no eyes lost ≥2 lines. No ectasia cases were observed during follow-up. Conclusion: LASIK surgery in Mexican Hispanic patients with thinner than “normal” corneas (<540 μm) is safe, efficient and predictable at 1 year follow up for myopic refractive corrections with no evidence of postoperative keratectasia.
Highlights
Laser in situ keratomileuses (LASIK) has been the treatment of choice for correcting corneal refractive errors since its introduction in early 1990 [1, 2]
Considered factors as a young age and high refractive correction to develop an Ectasia Risk Score Systems (ERSS) with the objective to assess the preoperative risk for developing ectasia after LASIK [13]
Evidence shows that factors as race [21, 22], age and gender [22, 23] altitude [24] and UV light exposure [25] may influence Central Corneal Thickness (CCT), different “normal” corneal thicknesses have been established amongst various research groups
Summary
Laser in situ keratomileuses (LASIK) has been the treatment of choice for correcting corneal refractive errors since its introduction in early 1990 [1, 2]. Considered factors as a young age and high refractive correction to develop an Ectasia Risk Score Systems (ERSS) with the objective to assess the preoperative risk for developing ectasia after LASIK [13]. The role of the Percent Tissue Altered (PTA) has been emphasized by Santhiago et al, as a robust risk indicator for developing ectasia after LASIK in the eyes with normal topography [14]. Either directly (ERSS) or indirectly (PTA), thin corneas have been considered as corneas with biomechanical liability and, likely to have an increased risk for developing ectasia after ablative surgery [13, 14]
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