Corneal neovascularization is a vision-threatening condition in which delicate blood vessels grow into the normally avascular cornea (the cornea has no blood vessels of its own). These vessels can extend from the limbus into the superficial or deep areas of the cornea, compromising its transparency.
It can be caused by inflammation related to infection, chemical injury, autoimmune conditions, immune hypersensitivity, corneal transplantation, trauma, contact lens complications, and other ocular pathologies. Immature new blood vessels may lead to lipid exudation, persistent inflammation, and scarring, thus threatening corneal transparency and visual acuity.
Contact lenses are the most common cause
Most corneal neovascularization is the result of extended contact lens wear that compromises the amount of oxygen reaching the cornea. Early, contact-lens-related corneal neovascularization usually presents as a superficial pannus, commonly at the superior limbus, under the upper lid, most likely related to hypoxia.
The role of hypoxia
Hypoxia occurs when the cornea does not get enough oxygen. It is the most common complication of contact lens wear, especially with extended-wear lenses. Because the cornea has no blood supply of its own, it receives oxygen only from the tears and directly from the atmosphere.
Physiologically, hypoxia causes cells to release inflammatory cytokines that can induce new vascular growth, which is as true in the cornea as it is in the retina. When the cornea is deprived of enough oxygen, the endothelial pump loses efficiency and can no longer maintain the relatively dehydrated state of the corneal tissue, so it begins to swell. When the decrease in available oxygen becomes chronic, the cornea responds by allowing tiny new blood vessels to grow. This is corneal neovascularization.
Occasionally, toric hydrogel contact lenses can also trigger a pannus, but at the lower limbus, where these lenses are thickest by design. Gas-permeable (GP) contact lenses carry a minimal risk of causing neovascularization, though they may if their oxygen permeability is low.
Who is at risk
- Contact lens wearers, especially those who are not compliant with lens care
- People with large amounts of nearsightedness (myopia)
- People who suffer from dry eye disease
- People with an ocular surface disease (rosacea, lupus)
- People with an underlying inflammatory disease (multiple sclerosis, Crohn’s disease)
- People with an untreated, or inadequately treated, infection of any ocular tissue
Treatment
Treating corneal neovascularization is challenging. However, a variety of treatment approaches, such as topical treatments, have shown varying degrees of effectiveness.
Many patients can be helped simply by decreasing wear from extended to daily use, and perhaps by increasing the oxygen permeability of their lenses, refitting from a hydrogel to a silicone hydrogel contact lens. The final clinical measure would be to discontinue contact lens wear altogether.
If vision dysfunction is severe, especially if it is due to lipid deposition at the corneal apex, the patient will most likely require a corneal transplant, whether lamellar or penetrating, to restore vision. You can learn more about the eye surgeries we offer in Roatan. A related contact-lens infection to be aware of is a corneal ulcer.
Prognosis
Once blood vessels have grown into the corneal tissue, they will not disappear completely. By increasing the oxygen reaching the cornea, it is possible to stop their growth, but even the best result will leave ghost vessels behind. If the cornea is again compromised for lack of oxygen, those vessels will fill up and begin to grow again.
Protect your vision
If you wear contact lenses and notice redness, irritation, or changes in your vision, don’t wait. At Dr. Reichmann’s clinic in Roatan we provide a complete eye exam and all of our eye care services. Book your appointment today to keep your eyes healthy.