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James Bradley Randleman, Eric Hwang, Julie M. Schallhorn; Identifying Optimal Scheimpflug Parameters to Predict Ectasia Risk after LASIK. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5774. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate Scheimpflug parameters in distinguishing eyes that developed ectasia after LASIK from eyes with uneventful follow-up after LASIK
Measurements from 33 eyes of 33 patients who developed ectasia after LASIK and 925 eyes of 925 patients with at least 2 years of uneventful follow-up after LASIK were evaluated with the Pentacam HR (Oculus, Inc.), including anterior curvature metrics, astigmatism, pachymetry, and keratoconus screening indices (30 variables). Results were adjusted with a Bonferroni correction and statistically significant variables were evaluated with receiver operating characteristic (ROC) curves.
The following measurements were statistically significant between groups (p<0.001): astigmatism, pachymetry values (apex, pupil, minimum, min y), index of surface variance (ISV), index of vertical asymmetry (IVA), keratoconus index (KI), central keratoconus index (CKI), index of height decentration (IHD) and Inferior Superior-Value (IS-Value) (p-value <.001). Eyes that developed ectasia had thinner corneas and higher screening values across all variables compared to control eyes. Highest AUC values were found for IS-value (0.750), KI (0.745) and PachyMin (0.709 ). No other metric achieved an AUC >0.7.
Eyes that developed ectasia post-LASIK had significantly greater surface asymmetry and thinner corneas compared to control eyes. While IS-value and KI were best, no individual Scheimpflug metric distinguished the two populations well.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Example topometric map from a patient who developed ectasia after LASIK
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