Corneal neovascularisation (NV) represents the main risk factor for immune rejection after corneal transplantation.^1,2 The healthy cornea devoid of blood vessels is said to be immune-privileged and when corneal grafts are placed into an avascular recipient corneal bed (low-risk keratoplasty) the two-year survival approaches 90% under treatment with a topical corticosteroid. However, a shift in the balance between angiogenic and anti-angiogenic stimuli, as can occur in the setting of infection, immune disregulation, or trauma, can lead to corneal NV.^1,3 The survival rates of corneal grafts placed onto vascularized recipient beds (high-risk keratoplasty) decrease significantly to below 50%.^{1, 4-6} Additionally, even in the low risk setting, mild angiogenesis develops after keratoplasty and increases the risk for immune rejection.

Several medical therapies including lubrication, non-steroidal anti-inflammatory medications, and corticosteroids have been used in an attempt to prevent progression of corneal NV with limited effect.⁷ Surgical therapies such as laser photocoagulation, diathermy and cauterisation of the vessels have also been shown to have positive but have had limited effect at regressing vessel growth.^8-10 However, new VEGF specific inhibitors have had very encouraging results in the treatment of neoplasia and more recently NV of the choroid and retina.

Bevacizumab (Avastin; Genentech, San Francisco, CA) is a humanised monoclonal antibody that binds and neutralises all human VEGF-A isoforms. It has already been approved by the US Food and Drug Administration (FDA) for the treatment of colon^11-12 cancer and has been reported to be effective in the treatment of choroidal, retinal, and iris neovascularisation from macular degeneration and diabetic retinopathy.^13-15 It has also been proven safe for intracameral injection as adjunctive treatment of neovascular glaucoma.¹⁶

Figure 1a: Patient 1 had a one-year history of ocular trauma and diffuse superficial and deep corneal NV with carbon debris in the conjunctiva and a cornea that was unresponsive to 8 months of topical 1% prednisolone acetate.

Given its clinical effect in the retina and systemic safety profile, we studied the use of topical bevacizumab as a potential treatment for inhibition and possible reversal of corneal NV in human subjects prior to corneal transplantation with the goal of improving the prognosis of graft survival in these subjects.

Study design & patient profiles

Our study was designed as an interventional case series and was approved by the Independent Review Board committee of Duke University. The off-label and compassionate use of bevacizumab as well as the potential risks, benefits and side effects of this medication were discussed extensively with each patient and their informed consent was obtained.

Figure 1b: Following treatment topically x4 daily for 25 days the superficial and deep stromal cornel NV was markedly reduced.

The formulation of bevacizumab for topical use was established by mixing the commercially available bevacizumab (Avastin 400 mg, 25mg/mL) with 0.5% (5 mg/mL) stock benzalkonium chloride (BAK) and sterile saline 0.9%. The final formulation yielded a concentration of bevacizumab 10 mg/mL (1.0%) in 0.01% BAK with a pH of 6.2. The solution was dispensed in 5 mL vials.

Figure 2a: Patient 2 had a history of ocular cicatricial pemphigoid complicated by a neurotrophic ulcer that healed with diffuse corneal NV, as well as punctuate and band keratopathy.

Two patients with moderate corneal NV and who were high risk for corneal transplantation were treated. Patient 1 was a 20 year-old male with a one-year history of ocular trauma and diffuse superficial and deep corneal NV with carbon debris in the conjunctiva and a cornea that was unresponsive to eight months of topical 1% prednisolone acetate (Figure 1A). Patient 2 was a 41 year-old male with history of ocular cicatricial pemphigoid complicated by a neurotrophic ulcer that healed with diffuse corneal NV, as well as punctuate and band keratopathy (Figure 2A). The NV was also unresponsive to a course of topical corticosteroids. Both patients had finger count vision in the affected eye.

Both patients were treated topically four times a day for 25 days. Each patient was examined at 3 days, 1 and 2 weeks, and 25 days. Superficial and deep stromal corneal NV was markedly reduced in Patient 1 (Figure 1B) and to a lesser degree in Patient 2 (Figure 2B). Systemic blood pressure remained at baseline level during the treatment period in both patients. No adverse ocular effects, such as conjunctivitis, increased epitheliopathy, conjunctival hyperemia, increased scarring, periocular changes, or burning on instillation, were noted. Patient 1 was followed for 9 months post-topical treatment and the corneal NV level returned, but to a level lower than pre-treatment baseline (Figure 3).