Corneal neo- (new) -vascularization (blood vessel growth), an in-growth of superficial or deep blood vessels into the cornea, is a sign of corneal oxygen deprivation and stress. This condition is most often associated with contact lens overwear. It can also be caused by toxic effects from lens or solutions, or traumatic causes such as damaged or heavily deposited lenses. It typically involves both eyes. Many cases of corneal neovascularization are asymptomatic, with some patients noticing redness around the cornea. Other symptoms include: eye pain, tearing and photophobia (light sensitivity), red redness, contact lens intolerance after a few hours of wear, and decreased vision.
Contact lens wear and corneal neovascularization
Most contact lenses interfere with oxygen transport to the cornea. The longer a lens is worn, the greater the risk for developing corneal hypoxia (lack of oxygen to the cornea), which induces metabolic changes in the corneal epithelium. In response to this oxygen depletion, blood vessels grow into the cornea in a dramatic attempt to help supply needed nutrients to the impoverished corneal tissues.
Prolonged lens wear (> 10hrs/day) carries a greater risk of corneal neovascularization than part-time wear, due to the continual presence of the lens on the eye. Increased blood vessel proliferation and redness are common findings in association with extended contact lens wear. Blood vessels extending beyond 2mm from the cornea margin, should be viewed with concern, as further progression can result in permanent contact lens intolerance and vision loss.
Depending on the severity of the condition, the management differs. It may range from the reduction of wearing time by a few hours to a temporary cessation of lens wear. Adequate time out of lenses will facilitate the healing of decompensated tissues.
The following should be considered when treating corneal neovascularization:
- Decrease wearing time
- Refit into high oxygen transmissibility lens material (high DK material). New silicon hydrogel material is 5-7X more oxygen permeable compared to the traditional soft plastics (eg Acuvue2). It will stop the progression of neovascularization and maybe worn for up to 24hrs a day without complications.
- Follow-up visits for progress check