This review aims to elucidate the key mechanisms behind the formation of corneal scars, and to give some consideration to the strength of the evidence behind those mechanisms identified. The review will firstly discuss the process of normal wound healing within the cornea that may precede scarring, and then examine three key factors within this process that have been suggested to contribute to corneal scarring: keratocytes and their activation by growth factors, collagen fibril organisation, and the role of neutrophils. Examination of the literature suggests that keratocyte activation by growth factors to their repair phenotype was found to be the most important factor in the formation of scars, while the disorganised deposition of collagen is a more contentious factor, and neutrophils have only relatively recently been thought to play a role and consequently little supporting evidence currently exists. This knowledge has allowed the development of targeted treatments, and perhaps further progress will be made in the future as our understanding of corneal scarring mechanisms improves.