Abstract
Purpose :
To evaluate the reliability of successive measurements of corneal tomography and biomechanics measured by Pentacam® and Corvis ST® (CST, Oculus, Wetzlar, Germany) in keratoconus (KC) patients at least two years after corneal crosslinking (CXL) compared to untreated KC cornea.
Methods :
Three successive corneal tomography (n=28 eyes of 21 patients) and biomecanic measurements (n=23 eyes of 16 patients) per eye were performed in the two years after CXL group (CXLG) including mild to advanced KC stages. Two control groups were formed consisting of non-operated and stage-matched KC corneas according to Belin’s ABCD classification, the first including KC cornea with three successive Pentacam measurements (n=26 of 24 patients, Pentacam controls, PC) and the second including KC cornea with three successive CST measurements (n=26 of 26 patients, CST controls, CSTC). Main outcome measures included K1, K2, Kmean, astigmatism for anterior and posterior corneal curvature, Kmax, thinnest pachymetry and the KC indices (tomography) and the biomechanical parameters that are included within the Corvis Biomechanical Index (CBI: A1 velocity, DA ratio 2mm, ARTh, integrated radius and SP-A1).
Results :
All tomographic parameters in the CXLG and PC group showed excellent reliability (Cronbach’s α > 0.95) as well as good intra-class correlation coefficients (ICC: CXLG > 0.92, PC: > 0.709), except for the Index of Height Asymmetry (Cronbach’s α: CXLG 0.855, PC: 0.605; ICC: CXLG: > 0.782, PC: > 0.585). The CST measurements showed better reliability in the CXLG than in the CSTC (Cronbach’s α, CXLG|CSTC: A1 velocity: 0.943|0.912, DA ratio 2mm: 0.931|0.906, ARTh: 0.976|0.433, SP-A1: 0.839|0.524). Only the integrated radius showed a better reliability in the CSTC (0.974) than the CXLG (0.857).
Conclusions :
Corneal tomography parameters showed excellent reliability independent of preceding CXL with the exception of the KC Index of Height Asymmetry (IHA). The biomechanical parameters turned out to show a better reliability two years or longer after CXL than in untreated cornea with the exception of integrated radius. Despite an overall high reliability of both devices, repeated CST measurements could be useful in the precise evaluation of progression using corneal biomechanics in untreated KC.
This is a 2021 ARVO Annual Meeting abstract.