Long-Term Changes Of Optical Coherence Tomography-Derived Corneal Parameters In Advanced Keratoconus

Optical coherence tomography-derived corneal parameters play a central role in the diagnosis and monitoring of keratoconus, particularly in detecting structural changes in the cornea and identifying disease progression. The anterior maximum corneal curvature (Kmax) and the minimum pachymetry are commonly used parameters in this context. This study investigated the long-term changes of these parameters in eyes with and without crosslinking treatment in patients with advanced keratoconus.

Department of Ophthalmology, Faculty of Medicine and University Hospital Carl Gustav Carus, TU Dresden, Dresden, Germany

This monocentric longitudinal study included 182 eyes of 182 patients with keratoconus and anterior Kmax of >60D. Each eye had at least two measurements. Eyes in the non-crosslinking group (n=78) had not undergone crosslinking before the first recorded measurement. In the crosslinking group (n=50), treatment had been performed at least 2 years before the first analyzed measurement. Inclusion criteria were applied at first recorded measurement, and eyes which received crosslinking afterwards remained in the analysis. Anterior Kmax and pachymetry at the thinnest point were compared between the first and last measurements using Wilcoxon test or paired t-test, depending on distribution, and p<0.05 was considered statistically significant.

Mean (±SD) follow-up was 1074±299 days and 703±437 days in crosslinking and non-crosslinking groups, respectively. At first measurement, crosslinking group had anterior Kmax 68.0±6.5D, posterior Kmax −12.2±5.1D, and thinnest pachymetry 387±58µm; mean changes (last-first) were +0.5±4.4D, −0.1±1.1D, and −5±25µm, respectively (all p>0.05). Non-crosslinking eyes showed 68.3±10.7D, −11.5±2.3D, and 402±64µm, with mean changes of +0.2±9.5D (p>0.05), -0.1±1.3D (p<0.01), and -6±31µm (p<0.01), respectively. During follow-up, crosslinking treatment was performed in 30% and 41%, an increase in anterior Kmax of >2.5D occurred in 26% and 25%, and a decrease of >2.5D in 16% and 16% of eyes in the crosslinking and non-crosslinking group, respectively.

In eyes with advanced keratoconus (Kmax >60D), optical coherence tomography-derived corneal parameters remained largely stable over long-term follow-up in both crosslinked and non-crosslinked groups. This indicates that stability of corneal parameters can be maintained over a longer period, even in advanced keratoconus. However, some eyes in both groups showed progression and required crosslinking.