Original research article EJO European Journal of Ophthalmology Ten years experience of corneal collagen cross-linking: An observational study of 6120 cases Ahmed Elmassry 1 , Osama Ibrahim Said Ahmed 1 , Moones F Abdalla 1 and Karim Gaballah 2 Abstract Purpose: To study the effect of corneal collagen cross-linking (CXL) using riboflavin and ultraviolet rays on cases of corneal ectasia in keratoconus cases, post-laser–assisted in situ keratomileusis ectasia, and pellucid marginal degener- ation and to present its long-term results over many years. Methods: This study was conducted throughout 10 “years” experience in corneal collagen CXL, including 6120 cases. The study consists of two parts: a retrospective and a prospective part. All patients in the retrospective part were operated by epi-off, while in the prospective part, the epi-on procedure was used. Also, other machines were used as Peschke Vario, Peschke Phoenix, and different types of riboflavin. The results were analyzed using SPSS. Results: The study showed stabilization ectasia in 95% of cases using our standard protocol, and this was proved by topography, pachymetry, refraction, and visual acuity. The effect of CXL was continued in 20%of cases, over a period of 3–5 years, some cases needed to repeat CXL due to the progression of corneal ectasia after cross-linking, in six eyes, that were rubbing their eyes and/or hormonal disturbance. Conclusion: Corneal collagen cross-linking CXL is an effective method to prevent the progression of corneal ectasia, whether primary or post-laser–assisted in situ keratomileusis, and the effect was stable over the years of study. Keywords Keratoconus, corneal ectasia, corneal collagen cross-linking, observational study Date received: 24 September 2019; accepted: 30 April 2020 Introduction Keratoconus is a progressive, non-inflammatory, bilat- eral, asymmetric disease, characterized by paraxial stromal thinning and weakening that leads to corneal surface distortion. 1 The problem of keratoconus has remained one of the major problems, affecting sight, with progress in corneal ectasia, and so the progression of myopia and astigmatism. 2 For many years, this problem had many trials to help the patient to have a useful vision, starting with glasses, contact lenses, and up to performing keratoplasty. 3,4 One of the other ectatic conditions, pellucid margin- al degeneration, is a bilateral, non-inflammatory disor- der, characterized by a peripheral band of thinning of the inferior cornea. 5,6 Also, after the evolution and the widespread of refractive surgery and the multiple fac- tors affecting the post-operative outcome, some related to the cornea as the corneal hysteresis, biomechanics, and corneal thickness, and others related to the opera- tive procedure of refractive surgery, amount of 1 Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt 2 Department of Ophthalmology, Helwan University, Helwan, Egypt Corresponding author: Ahmed Elmassry, Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Champollion Street, Al Mesallah Sharq, Al Attarin, 600 Horeya street, Zeezenia, Alexandria, Egypt, 21111. Email: ahmad.elmassry@gmail.com European Journal of Ophthalmology 0(0) 1–8 ! The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1120672120928921 journals.sagepub.com/home/ejo