Extreme Corneal Flattening Following Corneal Collagen Cross-Linking For Keratoconus
Published 2026 - 44th Congress of the ESCRS
Reference: POCOR380 | Type: Free paper | DOI: 10.82333/21eq-8q68
Authors: Dr Ecem Özkan Ceyhan* 1 , A/Prof. Betül Seher Uysal 1 , Prof. Dr Mehmet Cüneyt Özmen 1 , A/Prof. Mustafa Kamil Bilgihan 1
1Department of Ophthalmology,Gazi University Faculty of Medicine,Ankara,Türkiye
Purpose
This study aimed to evaluate the occurrence of extreme corneal flattening after CXL and to determine whether patients at risk can be identified based on early clinical and tomographic parameters.
Setting
Department of Ophthalmology, Gazi University, Ankara, Türkiye
Methods
This retrospective study included 94 patients with progressive keratoconus who underwent corneal collagen cross-linking (CXL) at Gazi University Faculty of Medicine between 2018 and 2022. Eyes treated with different CXL protocols including standard epithelium-off CXL, transepithelial diluted alcohol–assisted iontophoresis CXL, and sub400 CXL, and outcomes compared among the different protocols.
Maximum keratometry (Kmax) and thinnest corneal thickness values were recorded. Preoperative and final follow-up Kmax values used for analysis. Extreme corneal flattening was defined as reduction in Kmax greater than 5.0 diopters (D) during the follow-up. Patients divided into two groups based on the presence or absence of extreme corneal flattening.
Results
The study included 69(%73.4) male and 25(%26.6) female patients, with a mean age of 21.9±6.7 years and a mean follow-up of 3.53±2.09 years.
Extreme corneal flattening was observed in 13.8% (n=13) of eyes. Demographics, family history and ocular rubbing was similar among eyes with and without extreme flattening. On univariate analysis, preoperative Kmax (56.40±9.01) and thinnest corneal thickness (444.7±54.1) were significantly associated with extreme corneal flattening (both p<0.001). Higher preoperative Kmax was the only independent predictor of extreme corneal flattening (OR,1.45; p=0.003).No significant correlation was observed between follow-up duration and the degree of flattening (ρ=0.06, p=0.68), with a mean flattening of 3.67±2.87 D.
Conclusions
Extreme corneal flattening after CXL is mainly related to baseline corneal characteristics rather than demographic factors or the type of CXL protocol. Eyes with higher preoperative Kmax values and thinner corneas show a greater tendency toward extreme flattening during time. Recognizing this response pattern may help clinicians better anticipate postoperative corneal behavior and interpret long-term outcomes.