topography on Placido analysis, PTA” indicating risk of ectasia” was defined “abnormal “at as PTA 10 ≥40 Definition of topography” “normal In the study defining PTA, topography” was defined as and symmetric “normal “regular patterns (including round, oval, or symmetric bowtie patterns) or mildly asymmetric (steepening < 0.5 D and without skewed radial axis) based on Placido-disc analysis. 10 We included all cases with topographies scored 0 and 1 which fit this definition of “normal topography” for PTA analysis, and applied this definition of normal topography to our study as well. Topographies scored 3 and 4 were thus defined as having topography”. “abnormal In a subsequent study of eyes with suspicious and abnormal topography, no cut-off point was defined for the cases by the authors, although a lower PTA value was suggested in keeping with the findings that less tissue alteration was necessary to induce ectasia in eyes with biomechanically less stable corneas.11 Due to the paucity of data on this, we excluded all eyes with abnormal topography by the study definitions from PTA analysis. Subgroup analysis of eyes with normal topography In to directly compare the efficacy of PTA with the ERSS and SCORE Analyzer in predicting ectasia in our series of cases, an analysis of the sensitivity and specificity of ERSS and SCORE Analyzer was also performed in a subgroup of eyes with normal topography. We also determined in this subgroup if a single system or combination of systems was more accurate in predicting ectasia risk. Statistical analysis Statistical analysis was performed using IBM SPSS Version 19.0, with significance set at P< 0.05. Group data were compared using Fisher's Exact Test, Mann-Whitney U Test, Wilcoxon Signed Rank Test and McNemar Test as appropriate. Following determination of sensitivity
topography on Placido analysis, “abnormal PTA” indicating “at risk of ectasia” was defined as PTA ≥40 10 Definition of “normal topography” In the study defining PTA, “normal topography” was defined as “regular and symmetric patterns (including round, oval, or symmetric bowtie patterns) or mildly asymmetric (steepening < 0.5 D and without skewed radial axis) based on Placido-disc analysis. 10 We included all cases with topographies scored 0 and 1 which fit this definition of “normal topography” for PTA analysis, and applied this definition of normal topography to our study as well. Topographies scored 3 and 4 were thus defined as having “abnormal topography”. In a subsequent study of eyes with suspicious and abnormal topography, no cut-off point was defined for the cases by the authors, although a lower PTA value was suggested in keeping with the findings that less tissue alteration was necessary to induce ectasia in eyes with biomechanically less stable corneas.11 Due to the paucity of data on this, we excluded all eyes with abnormal topography by the study definitions from PTA analysis. Subgroup analysis of eyes with normal topography In to directly compare the efficacy of PTA with the ERSS and SCORE Analyzer in predicting ectasia in our series of cases, an analysis of the sensitivity and specificity of ERSS and SCORE Analyzer was also performed in a subgroup of eyes with normal topography. We also determined in this subgroup if a single system or combination of systems was more accurate in predicting ectasia risk. Statistical analysis Statistical analysis was performed using IBM SPSS Version 19.0, with significance set at P< 0.05. Group data were compared using Fisher's Exact Test, Mann-Whitney U Test, Wilcoxon Signed Rank Test and McNemar Test as appropriate. Following determination of sensitivity
JCRS-2017-Ectasia-Paper-v3-JBR-edits-05-16-17_CC-AS.docx