Corneal collagen crosslinking (CXL) has emerged as a frontline therapy in keratoconus and post-LASIK ectasia. This video lecture series explores the history and current uses of crosslinking, including epithelium-off, transepithelial, and concurrent crosslinking with corneal ring segments. In this segment, Dr. Peter Hersh discusses the clinical outcomes of CXL for keratoconus and corneal ectasia. Dr. Hersh reviews US trial data supporting the optical and visual outcomes, typical clinical course and timeline for visual improvement, and short-term effects on the cornea and epithelium. The studies also provide insight on subjective visual function and help predict which patients will gain the most benefit from CXL.