Longitudinal Trends In Corneal Collagen Cross-Linking (Cxl): Caseload And Demographic Shifts At A London Tertiary Centre (2013–2024)

Corneal collagen cross-linking (CXL) has been the primary treatment for progressive corneal ectasias, most commonly keratoconus, since its introduction in 2003. This is the first study to examine CXL trends over a course of a decade including the impact of the COVID-19 pandemic on case numbers. Understanding both how, and the rate at which CXL caseload is changing can help departments allocate their resources in the future.

A retrospective cohort audit was performed at a tertiary center in London, analysing all 424 CXL procedures on individual eyes conducted between 9th December 2013 and 1st September 2024.

Patient records were identified using Medisoft’s audit tool of CXL procedures since 2013 and subsequently manually reviewed to extract data on age, sex, operation date, and treatment indication. No patients were excluded and there were no incomplete patient records on the above parameters analysed. Trends in procedural volume, mean patient age, sex distribution, and clinical indications over time were evaluated using linear regression analyses (in yearly intervals) on GraphPad.

The number of CXL procedures increased significantly over time from 12 cases performed over 2013- 2014 to 99 cases in 2024 (p=0.00030, R²=0.75). Mean patient age showed a modest, non-significant decline (p=0.082, R²=0.0055) and the proportion of female patients rose significantly (p=0.017, R²=0.45). Keratoconus remained the predominant indication (97% of cases), with an increase in post-LASIK ectasia cases noted in 2023–2024 (80% of cases of subgroup). The other subgroup included patients with pellucid marginal degeneration (2 cases in 2024 only). The timing of the COVID-19 pandemic coincided with a temporary decline in procedural volume in 2020 (28 cases), followed by an increase in 2021–2022 (38 and 41 procedures respectively).

Over the past decade, the volume of CXL procedures has increased significantly, likely due to an expansion in the range of accepted indications, and recent post-pandemic service backlogs. Further multi-center studies are needed to confirm the generalisability of these trends.