Ectasia after laser in situ keratomileusis: lessons learnt from a multicentre case-control study

Session Details

Session Title: Keratoconus & Secondary Ectasia

Session Date/Time: Sunday 15/09/2019 | 08:00-10:00

Paper Time: 09:03

Venue: Free Paper Forum: Podium 2

First Author: : C.Chan SINGAPORE

Co Author(s): :    A. Saad   D. Gatinel                          

Abstract Details

Purpose:

To identify risk factors for ectasia after laser insitu keratomileusis (LASIK) and to validate the efficacy of current topography, tomography and risk assessment systems.

Setting:

Multicentre study involving 8 countries.

Methods:

Previously unpublished post-LASIK ectasia cases were identified from 9 institutions and analyzed. Consecutive patients with LASIK performed at least 5 years prior with no resultant ectasia were used as controls. Anterior curvature maps from pre-operative Orbscan IIz topographies were analyzed in a masked fashion and raw examination files tested with the SCORE Analyzer. Percent tissue altered (PTA) values and Ectasia Risk Score System (ERSS) scores were generated based on available preoperative and operative data. Only eyes with subjectively identified normal preoperative topography were tested with PTA.B. Threshold values for SCORE, ERSS and PTA were >0, >4 and >40 respectively.

Results:

Ectasia was seen in 31 eyes and 79 eyes were used as controls. In ectatic eyes, manifest refraction spherical equivalent was -4.93±1.82D, minimum corneal thickness 524.1±34.4m and residual stromal bed thickness(RSBT) 320.4±43.8m. Anterior curvature maps were subjectively classified as abnormal in 61.3% of ectatic eyes and 19.0% of controls. In all eyes, sensitivity and specificity for predicting ectasia occurrence of ERSS were 67.7% and 79.7% and for SCORE 64.5% and 100% respectively. In eyes with normal topography, PTA yielded sensitivity of 33.3% and specificity 85.9%. Area under Receiver Operating Characteristic curve was highest for SCORE(0.911) followed by ERSS(0.844) and PTA(0.557).

Conclusions:

High myopia, thin cornea and low RSBT were not risk factors for ectasia in our study. Topography-tomography gave the best specificity in predicting ectasia risk. The ERSS achieved the best sensitivity but at the expense of specificity. Further studies are required to validate PTA as a screening metric for ectasia.

Financial Disclosure:

receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented, travel has been funded, fully or partially, by a competing company, travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented, receives consulting fees, retainer, or contract payments from a competing company