Ectasia Risk Score System demonstrates excellent predictive ability

The Ectasia Risk Score System appears to be a valid method to determine eyes at risk for ectasia,said J. Bradley Randleman, MD, assistant professor of ophthalmology, Emory University, Atlanta, atRefractive Surgery Subspecialty Day.

The model was developed based on analysis of data collected in a retrospective review of 171 cases ofpost-LASIK ectasia and 186 controls with normal postoperative courses. Factors considered includedpatient age, gender, preoperative manifest refraction spherical equivalent, preoperative cornealthickness, predicted residual stromal bed thickness (RSB), and topographic patterns (normal,suspicious, or abnormal).

Through multivariate logistic regression analysis, abnormal topography, predicted RSB, young age, andlow preoperative corneal thickness were identified as the most important risk factors. Thosevariables, in addition to extreme myopia, were used to develop a risk score modeling system in whicheach criterion is assigned a point value and the cumulative risk scale score determines whether thepatient is at low, moderate, or high risk for developing post-LASIK ectasia.

Applying the scoring system to the study population, it identified 98% of controls as low risk but93% of ectasia cases as high risk, who would be recommended to be excluded from LASIK.

Subsequently, the model was validated in a novel LASIK patient population consisting of 50 ectasiacases and 50 controls. In the validation study, the predictive ability of the risk scoring system wasnearly identical to that observed in the initial population.

"We believe this scoring system represents a significant improvement upon previous screeningtechniques for identifying eyes at risk for post-LASIK ectasia. However, its validity has not beenestablished for surface ablation," said Dr. Randleman.