Late-onset corneal haze and myopic regression after photorefractive keratectomy (PRK)

Wound healing in the cornea: a review of refractive surgery complications and new prospects for therapy

PURPOSE

The corneal wound healing response is of particular relevance for refractive surgical procedures since it is a major determinant of efficacy and safety. The purpose of this review is to provide an overview of the healing response in refractive surgery procedures.

METHODS

Literature review.

RESULTS

LASIK and PRK are the most common refractive procedures; however, alternative techniques, including LASEK, PRK with mitomycin C, and Epi-LASIK, have been developed in an attempt to overcome common complications. Clinical outcomes and a number of common complications are directly related to the healing process and the unpredictable nature of the associated corneal cellular response. These complications include overcorrection, undercorrection, regression, corneal stroma opacification, and many other side effects that have their roots in the biologic response to surgery. The corneal epithelium, stroma, nerves, inflammatory cells, and lacrimal glands are the main tissues and organs involved in the wound healing response to corneal surgical procedures. Complex cellular interactions mediated by cytokines and growth factors occur among the cells of the cornea, resulting in a highly variable biologic response. Among the best characterized processes are keratocyte apoptosis, keratocyte necrosis, keratocyte proliferation, migration of inflammatory cells, and myofibroblast generation. These cellular interactions are involved in extracellular matrix reorganization, stromal remodeling, wound contraction, and several other responses to surgical injury.

CONCLUSIONS

A better understanding of the complete cascade of events involved in the corneal wound healing process and anomalies that lead to complications is critical to improve the efficacy and safety of refractive surgical procedures. Recent advances in understanding the biologic and molecular processes that contribute to the healing response bring hope that safe and effective pharmacologic modulators of the corneal wound healing response may soon be developed.

Corneal wound healing

PURPOSE

To examine the latest theories in understanding wound healing, primarily as it pertains to refractive surgery but also, briefly, incisional surgery and nonsurgical corneal conditions (iatrogenic injury and noninfectious corneal ulcers).

RECENT FINDINGS

Corneal wound healing involves transformation of fibroblasts; intercellular signaling-for example between epithelial and stromal cells-from cytokines, neuropeptides, growth factors, and chemokines; action of matrix metalloproteinases; and protection of tissue from free radical damage. There may be a common wound healing pathway after different types of surgery and injury to the cornea-for example, the wound healing cascades after laser in situ keratomileusis and photorefractive keratectomy may be similar, and yet the effects on the cornea differ because of the extent of disruption to the basement membrane-but the outcomes may depend on small differences in the cascade.

SUMMARY

Interest in the study of corneal wound healing has increased with the proliferation of keratorefractive surgery. Important contributions come from intercellular signaling, fibroblast transformation, remodeling of the extracellular matrix, and free radical scavengers. Despite these advances, a formalized, unified vision of the wound healing cascade remains elusive.