Managing Corneal Neovascularization
BY WILLIAM L. MILLER, OD, MS, PHD, FAAO
Vascularization of the cornea can have devastating visual consequences. Several infectious diseases, most notably herpes simplex keratitis and trachoma, can lead to profound blood vessel growth. Post-surgical corneas, such as those that have undergone penetrating keratoplasty (PKP) and radial keratotomy (RK), can also exhibit neovascularization; in the case of PKP, this can indicate that the graft is failing.
Neovascularization can occur in cases of contact lens noncompliance and in susceptible lens wearers; it is associated with the lens’ oxygen transmissibility. Between 11% and 18% of hydrogel lens wearers experience neovascularization depending on whether they are in a daily wear or extended wear modality (Keech et al, 1996; Chalmers et al, 2005).
Silicone hydrogel lenses have greatly reduced the incidence of both neovascularization and limbal hyperemia (Dumbleton et al, 2001; Papas et al, 1997). However, every cornea has different oxygen demands and depends on the health status of the tissue, thereby warranting close inspection of any lens wearer for the appearance of neovascularization.
Managing soft lens-induced neovascularization may require discontinuation of contact lens wear. Most cases necessitate a refit into a lens with a higher Dk/t, which in some patients may be a GP lens. Strategies beyond this are rarely indicated unless a patient has a surgically altered cornea, such as post-PKP or post-RK.
In disease- or surgically induced neovascularization, therapeutic intervention is often required regardless of contact lens wearing status. Commonly, this involves topical steroids, which calm the inflammatory cascade’s stimulus to neovascularization. Dosing depends on the level of inflammation and the severity of the neovascularization, but in most cases administration is four times a day. In cases of neovascularization and possible PKP graft rejection, the steroid may be continued for a longer time, albeit fewer times per day.
Figure 1. RK neovascularization in a patient wearing a soft contact lens.
The side effects of topical steroids, such as elevated intraocular pressure, should be monitored over the course of therapy. Nonsteroidal anti-inflammatory topical medications can also be used, especially when side effects of topical steroids are a concern.
Surgical intervention has also been employed, especially in cases of recalcitrant neovascularization. Procedures might include argon laser photocoagulation of the blood vessels, photodynamic therapy, electrocoagulation, and stem cell transplantation (Gordon et al, 2002; Sugisaki et al, 2008; Kwitko et al, 1995).
More recent work has focused on the off-label use of anti-VEGF (vascular endothelial growth factor) therapy. Several clinical trials have shown promising results, but side effects may include corneal thinning and loss of epithelial integrity, likely because of VEGF’s importance in maintaining normal corneal nerve function and normal wound healing (Koenig et al, 2009; Vassileva and Hergeldzhieva, 2009; Uy et al, 2008). It has been administered topically and via subconjunctival and stromal injections. CLS
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Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a consultant or advisor to Alcon and Oasis Medical and has received research funding from CooperVision, Contamac, and SynergEyes and lecture or authorship honoraria from Alcon. You can reach him at email@example.com.