Update on Therapeutic Approaches to Corneal Neovascularisation

Abstract

A healthy cornea is a nonvascularized, transparent tissue. It is nourished by diffusion through the tear film, aqueous fluid and neurotrophins supplied by the corneal innervation. The cornea is devoid of both blood and lymphatic vessels, which makes it an immunologi-cally privileged tissue. Corneal neovascularization develops due to an imbalance between angiogenic and anti-angiogenic factors and can lead to a significant decrease in visual acui-ty. It may cause scarring, lipid keratopathy, and corneal edema. The resulting pathological vascularization of the cornea reduces its immune privilege and significantly worsens the prognosis after subsequent penetrating keratoplasty, increasing the risk of rejection of the transplanted flap. Neovascularization is favored by many disease processes, including auto-immune diseases, viral inflammations, mainly herpes and varicella-zoster, and blepharitis [1]. There are several options to treat corneal neovascularization, both pharmacological and surgical. Angiostatic treatment involves inhibiting the growth of new vessels by suppressing inflammatory responses. VEGF inhibitors, steroids, cyclosporine A, and amniotic membrane grafts secured to the cornea work this way. VEGF inhibitors are the agents with the direct and most potent angiostatic effect. Angioregressive treatment, on the other hand, results in the regression of already existing pathological vessels. This therapy is also based on VEGF inhibitors, which, however, have the most potent effect on newly formed and small vessels but are less effective in reducing large-caliber and mature vessels. A more effective method for such vessels is ablation, which involves surgical closure. The most commonly used an-gio-occlusive method is needle diathermy and argon or yellow laser therapy. In advanced corneal neovascularization, corneal transplant surgery may be necessary. It is best performed after pretreatment with anti-VEGF preparations, often continued after corneal transplanta-tion to reduce the risk of transplant rejection [2]. This paper discusses the pathogenesis of corneal neovascularization and the current and future trends in its treatment.