Wound Healing In Glaucoma

The goal of wound healing in most surgeries is to bring the injured tissue back to its original state to prevent the wound from reopening. However, in glaucoma surgery, the goal is to have incomplete wound healing. Scar formation prevents the filtering mechanism and bleb from functioning properly, leading to poor pressure control and failure of the surgery. However, if there is too little wound healing, surgical failure may be marked by overfiltration and hypotony. Several modulators are currently used in conjunction with glaucoma surgery, and new targets are under investigation to improve our ability to control the healing process. Normal wound healing occurs in 3 phases: the inflammatory phase, the proliferative/repair phase, and the remodeling phase. In the inflammatory phase, blood cells and plasma proteins are released around the wound site. These proteins attract other wound healing factors, such as cytokines and growth factors. White blood cells are also recruited to the site, clearing out undesired cellular debris through phagocytosis. Additionally, platelet aggregation and fibrin clot formation occur. In the proliferative/repair phase, fibroblasts, crucial cells for tissue repair and scarring, begin reforming the extracellular matrix (ECM) and other components of connective tissue. Angiogenesis also occurs, and the wound begins to close. In the final phase, blood vessels are resorbed and fibroblasts disperse. Fibroblasts produce matrix metalloproteinases that, along with collagen and elastin, allowing for wound remodeling and scar formation. The modulators used in glaucoma surgery, as well as new agents in development, disrupt various aspects of this cycle. Use of topical corticosteroids in conjunction with filtering surgery is a routine part of postoperative management and has been for many decades. Corticosteroids blunt the wound healing response by altering the inflammatory phase through reducing the amount of inflammatory cells and cytokines that migrate to the wound site. Corticosteroids also prevent the complexing and conversion of inflammatory mediators, as well as reduce vascular permeability to limit mobility of wound healing factors to the wound site.