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Age, corneal shape influence risk for ectasia after LASIK
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WASHINGTON — Abnormal corneal shape and younger age pose the greatest risk for ectasia after LASIK, according to Steven Schallhorn, MD, who reported on an ongoing analysis of a large cohort of patients.
“We have a consecutive series of patients that we’re following that were treated years ago from 2007 to 2011,” Schallhorn said at Refractive Day during the American Society of Cataract and Refractive Surgery meeting. These patients represent nearly 200,000 patients who underwent laser vision correction. “It takes time if ectasia is going to become manifest. In that data set, we’ve seen 213 eyes of 155 patients who have developed ectasia.”
Because the cohort is a consecutive group of patients, not case controlled, “We can do things with this data that you cannot do with previous studies,” he said. Univariate analysis found corneal steepness and asymmetric bow tie not to be related to ectasia. However, for the number of characteristics that were related to ectasia, their interrelationships were unknown. Multivariate analysis found forme fruste keratoconus alone had 20 times the risk for ectasia development, a 1 in 160 chance, according to Schallhorn.
For ectasia cases after LASIK, the analysis found 40% occurred in patients older than 30 years, and 98% of patients had 8 D or less of myopia. Central cornea thickness greater than 510 µm was present in 80% of cases, and residual stromal bed greater than 300 µm occurred in 88%. Thirty percent of ectatic patients had normal topography.
“When we do careful ... analysis, there are two that clearly stand out: abnormal corneal shape and age. However, patients who have no risk factors can and do develop ectasia despite our best efforts at screening them. The bottom line is, we cannot eliminate the risk of ectasia, but what might be happening is that patients who are going to develop keratoconus are going to develop keratoconus regardless of whether we perform laser vision correction on them,” Schallhorn said. – by Patricia Nale, ELS
Reference:
Schallhorn S. Can we eliminate the risk of ectasia? Presented at: American Society of Cataract and Refractive Surgery annual meeting; April 13-17, 2018; Washington.
Disclosure: Schallhorn reports he is the chief medical officer for Zeiss and an advisor for Optical Express.