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Preop risk factors for ectasia post-LASIK identified
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ATLANTA — The risk for developing corneal ectasia after LASIK is higher for patients with initial high myopia and forme fruste keratoconus or low residual stromal beds, according to researchers here.
J. Bradley Randleman, MD, and colleagues of the Emory Vision Refractive Surgery Center conducted a retrospective review of 10 eyes treated with LASIK that developed corneal ectasia. They compared this group to two control groups with normal postoperative courses and a third group of 33 cases of ectasia previously reported in the literature.
The first control group included 100 patients with an average preop refraction of –5.37 D. The second control group comprised 100 patients with a mean preop refraction of –8.69 D. The average follow-up time was 23.4 months after LASIK. On average, if ectasia developed it did so 16 months after LASIK.
Preoperatively, 88% of ectasia cases met criteria for forme fruste keratoconus, compared with 2% of the first control group and 4% from the second control group (P < .0000001).
Seven eyes (70%) of the study group that developed ectasia had residual stromal beds of less than 250 µm; 16% of eyes in the first control group and 46% of the second control group had similar stromal bed sizes.
Only 10% of eyes lost more than one line of best corrected visual acuity and all patients eventually achieved corrected vision of 20/30 or better.
“Each of our cases had at least one predictive risk factor other than high myopia,” the study authors wrote in the February issue of Ophthalmology. “This study represents the first published comparison of patients developing ectasia after LASIK with control populations that did not develop ectasia, and it demonstrates significant differences in preoperative refraction, preoperative topography and residual stromal bed thickness between these populations.”