Validation of an Objective Scoring System for Subclinical Keratoconus Detection and Post-LASIK Ectasia Risk Assessment in Asian Eyes

Tuesday, April 21, 2015: 8:11 AM
Room 1B (San Diego Convention Center)
Cordelia Chan, FRCS(Ed)
Marcus Ang, MBBS, FRCSEd
Alain Saad, MD
Damien Gatinel, MD

To investigate the efficacy of the SCORE Analyzer (Bausch+Lomb TechnoLas, Germany) in the detection of early subclinical keratoconus and as a risk assessment system for post-LASIK keratectasia in Asian eyes

We retrospectively evaluated cornea topographies with the Orbscan IIz system and independently tested them with the SCORE Analyzer through masked investigators. Eyes were classified into two groups: 1.Forme fruste keratoconus (FFKC) group were clinically and topographically normal eyes with definite keratoconus in the contralateral eye. 2.Control group involved normal pre-operative topographies of patients with LASIK performed at least 4 years prior with no resultant ectasia. Main outcome measures were accuracy parameters: sensitivity, specificity, positive and negative predictive values (PPV, NPV). Parameters involved in the SCORE algorithm were compared in both groups.

We analyzed 128 Orbscans of 128 Asian patients. There were 24 FFKC eyes and 104 controls. In the FFKC group, the SCORE was negative in 7 eyes (false negative) and 2 in the control group were positive (false positive). Sensitivity was 70.83%, specificity 98.08%, PPV 89.47% and NPV 93.58%. Irregularity at 3mm, thinnest pachymetry (TP), central and thinnest pachymetry difference (CP-TP), vertical decentration of thinnest point (TP-Y), maximum posterior elevation (MPE) and anterior elevation of thinnest point (AETP) were statistically significantly different in both groups. 

The SCORE Analyzer showed excellent specificity and good sensitivity in the detection of early subclinical keratoconus in Asian eyes. The SCORE Algorithm and its defining parameters were found to be valid and consistent, making it a good objective risk assessment system for post-LASIK ectasia.