Model evaluates risk assessment for ectasia after LASIK

Investigators at Emory University, Atlanta, have developed a comprehensive weighted risk factor scalethat should significantly improve the identification of eyes at high risk for development of cornealectasia following LASIK. J. Bradley Randleman, MD, assistant professor of ophthalmology, section ofcornea, external disease, and refractive surgery at Emory University, along with several colleagues,devised the model after conducting a retrospective review of all ectasia cases seen at Emory andreported in the literature. They found 171 cases and compared them with 186 controls.

Topographic patterns were classified as normal or symmetrical, suspicious, or abnormal. Theinvestigators found significant differences between patients with ectasia and the controls for all ofthe variables they assessed. Patients with ectasia were younger, more myopic, had thinner corneaspreoperatively, had a higher percentage of abnormal topographies, and had significantly thinnerresidual stromal beds. Investigators also analyzed a subgroup of patients and controls for whom theyhad all available information and found similar differences between them.

From this subgroup they determined that the most important risk factors, in order, were abnormaltopography, residual stromal bed, age, and preoperative corneal thickness. This information was usedto develop a risk modeling system in which each risk factor was given a weighted point value. In thescoring system, 0 to 2 was low risk, a level at which it was safe to proceed with LASIK, and 3 wasmoderate risk, meriting a cautious approach to LASIK and consideration of other options. A score of 4or above was high risk, a level at which LASIK should not be performed.

Applying this scoring system to their study groups, the investigators found that 98% of the controlpopulation was identified as low risk and 93% of the patients with ectasia were identified as highrisk. They would not have been offered surgery based on this model, Dr. Randleman said.

He pointed out, however, that eyes with no known risk factors can develop ectasia and that patientswho have one or more risk factors will not necessarily have postoperative complications. Dr. Randleman'spresentation was selected as the best of the refractive free papers session.