الفهرس | Only 14 pages are availabe for public view |
Abstract cornea and cartilage are considered the only tissues in the human body that lack of the blood vessels. The cornea has important mechanisms to maintain its avascularity (corneal angiogenic privilege). Disturbance of the angiogenic privilege of the cornea occursas a result of several diseases: infections as trachoma and herpetic keratitis, hypoxia (as in contact lens), and limbal barrier defects (as in chemical burns). Usually, corneal hem-angiogenesis is accompanied by lymph- angiogenesis. These lead to impairing of vision by inducing lipid keratopathy, stromal edema and hemorrhage. They also contribute in immune graft rejection after keratoplasty. Corneal avascularityis achieved by balancing between angiogenic stimulating factors and angiogenic inhibiting factors, both secreted in normal cornea. However, when the balance is shifted towards angiogenic growth factors such as VEGF, PDGF, FGF, etc., corneal angiogenesis will take place. Pathologic corneal lymphatic vessels are invisible by ordinary examination by the slit-lamp magnification, but can be visualized by specific immunohistochemical markers and confocal microscopy. The new anti-angiogenic and antilymph-angiogenic therapies can inhibit corneal (NV) and improve graft survival after both low and high-risk keratoplasty by inhibition of immune graft rejections. Antiangiogenic therapy includes three categories: angiostatic e.g. steroids, ionidizing radiation, anti-VEGFs, and anti-IRS-1 eye drops; angioregressive e.g. anti-VEGF, endostatin; and angio-occlusive e.g.PDT, fine needle diathermy combined with topical anti-VEGFs. |