Evaluation of keratoconus progression. Issue 4 (1st June 2018)

• Record Type: Journal Article
• Authors: Shajari, Mehdi; Steinwender, Gernot; Herrmann, Kim; Kubiak, Kate Barbara; Pavlovic, Ivana; Plawetzki, Elena; Schmack, Ingo; Kohnen, Thomas
• Is Part Of: British journal of ophthalmology. Volume 103:Issue 4(2019)
• Page Start: 551
• Page End: 557
• Publication Date: 2018-06-01
• Subjects: Cornea; Ophthalmology -- Periodicals; 617.7
• DOI: 10.1136/bjophthalmol-2017-311651
• Languages: English
• ISSNs: 0007-1161

Abstract

Abstract : Aim: To define variables for the evaluation of keratoconus progression and to determine cut-off values. Methods: In this retrospective cohort study (2010–2016), 265 eyes of 165 patients diagnosed with keratoconus underwent two Scheimpflug measurements (Pentacam) that took place 1 year apart ±3 months. Variables used for keratoconus detection were evaluated for progression and a correlation analysis was performed. By logistic regression analysis, a keratoconus progression index (KPI) was defined. Receiver-operating characteristic curve (ROC) analysis was performed and Youden Index calculated to determine cut-off values. Results: Variables used for keratoconus detection showed a weak correlation with each other (eg, correlation r=0.245 between RPImin and Kmax, p<0.001). Therefore, we used parameters that took several variables into consideration (eg, D-index, index of surface variance, index for height asymmetry, KPI). KPI was defined by logistic regression and consisted of a Pachymin coefficient of −0.78 (p=0.001), a maximum elevation of back surface coefficient of 0.27 and coefficient of corneal curvature at the zone 3 mm away from the thinnest point on the posterior corneal surface of −12.44 (both p<0.001). The two variables with the highest Youden Index in the ROC analysis were D-index and KPI: D-index had a cut-off of 0.4175 (70.6% sensitivity) and Youden Index of 0.606. Cut-off for KPI was −0.78196 (84.7% sensitivity) and a Youden Index of 0.747; both 90% specificity. Conclusions: Keratoconus progression should be defined by evaluating parameters that consider several corneal changes; we suggest D-index and KPI to detect progression.