OBJECTIVEThe aim of this review is to comprehensively and unbiasedly summarize the improvements in the techniques for classical corneal collagen cross-linking (CXL) by covering the reasons for this improvement, measure, and effect to approach the future direction of the CXL.

DATA SOURCESAll articles used in this review were mainly retrieved from the PubMed database.

STUDY SELECTIONOriginal articles and reviews were selected if they were related to the improvement in the technique of classical CXL. Data were mainly extracted from 94 articles, which are listed in the reference section of this review.

RESULTSThis innovative research involves every step such as instrument preparation, epithelial management, riboflavin instillation, and UVA irradiation. These clinical and experimental results seem promising.

CONCLUSIONSCXL treatment is the only recent promising method for preventing the progress of keratoconus. The limitations and potential complications that accompany classical CXL such as corneal thickness limitations, ultraviolet-A (UVA) light injury, and the impact of de-epithelialization encourage people to research new improvements in techniques. While this research needs to be further investigated, we hope our review can help related researchers and patients.