A modified risk assessment scoring system for post laser in situ keratomileusis ectasia in topographically normal patients

Abstract

Purpose:To evaluate and modify the Randleman Ectasia Risk Score System for predicting post-laser in situ keratomileusis (LASIK) ectasia in patients with normal preoperative corneal topography.Methods:In this retrospective study we reviewed data from 136 eyes which had undergone LASIK including 34 ectatic and 102 normal eyes between 1999 and 2009. After determining the sensitivity and specificity of the Randleman system, a modified model was designed to predict the risk of post-LASIK corneal ectasia more accurately. Next, the sensitivity and specificity of this modified scoring system was determined and compared to that of the original scoring system.Results:In our sample, the sensitivity and specificity of the Randleman system was 70.1% and 50.5%, respectively. Our modified model included the following parameters: preoperative central corneal thickness, manifest refraction spherical equivalent, and maximum keratometry, as well as the number of months elapsed from surgery. Sensitivity and specificity rates of the modified system were 74.2% and 76.2%, respectively. The difference in receiver operating characteristic curves between the Randleman and modified scoring systems was statistically significant (P<0.001). The best sensitivity and specificity for our model occurred with a cumulative cutoff score of 4.00; a low risk was considered if the score was ≤4.00, and high risk was defined with a score > 4.00.Conclusion:Our modified ectasia risk scoring system for patients with normal corneal topography can predict post LASIK ectasia risk with acceptable sensitivity and specificity. However, there are still unidentified risk factors for which further studies are required.

Commentary: Ectasia after keratorefractive surgery: An ounce of prevention is worth a pound of cure

“…The various risk factors that have been studied are: younger age, high manifest refraction spherical equivalent (more ablation depth), a thin cornea (lesser than 500 μm), anterior topographic irregularities, high posterior elevation float (>15 μm at the thinnest point), an Ectasia Risk Score higher than 3, low residual stromal bed thickness (RSB), high percent tissue thickness alteration (PTA), etc. [ 1 2 3 ]…”