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Corneal neovascularization occurs when blood vessels grow in the cornea, usually due to oxygen deprivation. Contact lens wear is a common cause, with higher risk for those with underlying conditions. Treatment may include discontinuing contact use, topical corticosteroids, or corneal transplantation. Pre-transplant, aggressive treatment of neovascularization is necessary to reduce rejection risk.
Corneal neovascularization refers to the growth of blood vessels in the cornea, which is normally devoid of blood vessels. This most frequently results from corneal oxygen deprivation or hypoxia. In response to this hypoxia, the body attempts to supply the deprived corneal tissues with needed nutrients and oxygen by creating new blood vessels. During the early stages, this abnormal blood vessel growth may produce no signs or may cause a variety of symptoms, including eye pain and excessive tearing, sensitivity to light, redness, intolerance to contact lenses, and decreased vision.
Normally, the cornea is avascular, or without blood vessels, because it needs to be transparent to allow light to pass through for proper focus and vision. This lack of blood vessels means that the cornea has to absorb oxygen from the air, and therefore any process that inhibits this absorption can cause corneal neovascularization. Most commonly, this condition is caused by contact lens wear, with a higher incidence in prolonged contact lens wearers, anything over about 10 hours a day.
Reported prevalence ranges from 1 to 30% among contact lens wearers, with a higher incidence in those wearing traditional soft plastic lenses than in those wearing newer, oxygen permeable lenses. An increased risk is reported in contact lens wearers who have several underlying conditions, including high myopia, chronic dry eye, or ocular surface disease, which generally defines a group of disease processes affecting the cornea and/or conjunctiva. Other causes of corneal neovascularization include eye trauma, toxic chemical injury, immunologic disease, infectious diseases such as keratitis, and corneal graft rejection.
In many cases, contact lens wearers who experience only superficial neovascularization can promote healing by discontinuing contact use or decreasing wear time and switching to oxygen permeable lenses. For cases of nonsuperficial neovascularization, more aggressive treatments, such as the application of topical corticosteroids, hyperbaric oxygen treatment, or photodynamic therapy, may be required. Occasionally severe corneal neovascularization can cause corneal scarring, leading to corneal opacity and severe vision problems, in which cases corneal transplantation may be necessary.
A cornea transplant, also known as a corneal graft or keratoplasty, is a surgical procedure that replaces a damaged cornea with corneal tissue from a recently deceased donor. These transplants often have a much lower rejection rate than other transplant procedures because the cornea is usually devoid of blood and lymph vessels; therefore, the presence of these blood vessels before transplantation is a risk factor for rejection. Furthermore, even patients who have not had corneal neovascularization before surgery can develop this condition after undergoing a corneal transplant, leading to an increased risk of rejection. For this reason, aggressive treatment of the neovascularization may be necessary prior to corneal transplant surgery to ensure a lower chance of graft rejection.
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