Characteristics of Corneal Ectasia after Myopic LASIK

Abstract

Abstract: : Purpose: Corneal ectasia after LASIK for myopia is a rare (<1%) but serious complication of this elective surgical procedure. There are numerous cases reported in the literature with no accepted definition of the condition or comprehensive explanation of its cause. A retrospective analysis was conducted to define the common characteristics of corneal ectasia after LASIK, and comparisons were made with successful post-operative LASIK patients. Methods: A MEDLINE search for "LASIK" and "ectasia" yielded 17 relevant articles published prior to August 2002; (n = 73 eyes, 54 patients). A control group (n = 99 eyes from 61 patients) was randomly selected from a clinic-based sample of successful LASIK patients with 12 months of follow-up after treatment. Statistical comparisons were made using the Mann-Whitney test. Results: The age of the ectasia patients was 35 ± 9.8 years (mean ± SD) and 44 ± 9 years for the controls (p < 0.001). A summary of preoperative data is shown in Table 1. The mean postoperative time to diagnosis was 12 months. Postoperatively, the ectasia group had significantly greater residual myopia (–4.6 ± 5.7 D), increased corneal toricity (+1.8 ± 3.5 D) with increased oblique astigmatism (+0.9 ±1.3 D), and an average loss of 4 ± 4 lines of best-corrected visual acuity (all p < 0.001). On average, ectasia patients received significantly deeper ablations (115 ± 45 µm vs. 49 ± 22µm, p < 0.001) and had thinner residual stromal bed thickness (270 ± 83 µm vs. 332 ± 46µm, p < 0.001). Ectasia patients were treated by penetrating keratoplasty (40%) or by rigid contact lenses (60%). Conclusions: Several clinical and surgical factors were significantly different between reported cases of LASIK ectasia and patients with uncomplicated surgical outcomes. These findings suggest LASIK ectasia may be associated with magnitude of treatment, as well as thinner corneas and greater corneal toricity. Table 1: Preoperative comparison data for cases and controls. All mean differences were significant (p<.001)  

Keywords: refractive surgery: LASIK • refractive surgery: complications • clinical (human) or epidemiologic studies: out