Corneal neovascularization. Pathogenesis and inhibition.

Corneal neovascularization (CNV) can cause significant visual loss because of the scarring and lipid deposition that frequently accompany it. In addition, penetrating keratoplasty in a vascularized recipient carries a significant risk of failure from allograft rejection. Frequently CNV is induced by nonspecific inflammatory stimuli, mediated primarily by polymorphonuclear neutrophils. Neovascularization can also be associated with specific corneal immune reactions, such as herpes simplex keratitis. Immunologically mediated CNV may be more amenable to treatment than CNV that results from nonspecific inflammation. Photodynamic therapy (PDT) following the intravenous injection of hematoporphyrin derivative or purified dihematoporphyrin ether (DHE) has been shown to suppress tumor growth and blood vessel growth in the eye. We have developed a murine model of CNV induced by the intrastromal injection of stimulated lymphocytes or interleukin-2 (IL-2). We have noted corneal DHE retention following its intravenous injection in mice with IL-2 induced CNV. Preliminary studies indicate that PDT can induce regression of CNV in these mice. Other recent studies that have enhanced our understanding of the pathogenesis and treatment of CNV are reviewed, and directions for future research are discussed.