Avastin (bevacizumab) is a medication originally developed and approved for treating various types of cancer. Although initially intended for oncology, Avastin has been widely repurposed in ophthalmology to treat serious, vision-threatening eye diseases. The drug is administered via an injection directly into the eye, a practice considered “off-label” by the FDA but broadly accepted due to extensive clinical evidence of its safety and effectiveness.
How the Medication Works
The efficacy of bevacizumab in the eye centers on its role as an anti-vascular endothelial growth factor (anti-VEGF) agent. Vascular Endothelial Growth Factor (VEGF) is a protein that, when produced in excess in the eye, signals for the growth of abnormal and leaky blood vessels. This process, known as neovascularization, leads to fluid leakage and swelling at the back of the eye, severely affecting vision.
Avastin is a monoclonal antibody designed to bind to and neutralize active forms of VEGF. By blocking this protein, the medication prevents VEGF from interacting with receptors on endothelial cells, the building blocks of blood vessels. Blocking this interaction halts the proliferation of abnormal vessels and reduces the fluid they leak into the macula, helping to stabilize or improve vision. The drug is injected directly into the vitreous cavity to achieve high local concentrations where the pathology is occurring.
Eye Conditions Treated
The primary conditions treated with Avastin injections are characterized by the damaging effects of excessive VEGF activity. Wet Age-Related Macular Degeneration (Wet AMD) is a leading indication, where abnormal blood vessels grow beneath the retina and macula. This causes rapid vision loss through bleeding and fluid leakage. Anti-VEGF therapy shrinks these new vessels, preventing further damage to the macula, which is responsible for sharp, central vision.
Avastin is also a common treatment for Diabetic Macular Edema (DME), a complication of diabetic retinopathy. In DME, damaged blood vessels leak fluid into the macula, causing the retina to swell and distort central vision. The injection stops the leakage, allowing the swelling to subside.
Retinal Vein Occlusion (RVO), including Central and Branch Retinal Vein Occlusions, is another condition treated with Avastin. When a retinal vein is blocked, pressure builds up, leading to fluid and blood leakage into the retina and resulting in macular edema. The anti-VEGF action reduces this secondary swelling caused by poor blood flow.
What Happens During the Injection Procedure
The intravitreal injection procedure is typically performed in an office setting and takes only a few minutes, though the overall visit is longer due to preparation. The process begins with topical anesthetic drops to thoroughly numb the eye’s surface, ensuring minimal discomfort during the injection. The eye and surrounding area are meticulously cleansed using an antiseptic solution, most commonly povidone-iodine, to reduce the risk of infection.
A small instrument called an eyelid speculum is often used to gently keep the eyelids open and prevent blinking during the brief procedure. The ophthalmologist asks the patient to look in a specific direction, and a tiny needle containing the Avastin is inserted into the vitreous cavity through the sclera (the white part of the eye). The injection site is carefully measured, usually 3.5 to 4 millimeters from the limbus (the edge of the cornea), to avoid damaging the lens or the retina.
The drug is slowly released into the back of the eye, and the needle is immediately removed. Most patients feel only a sensation of pressure. Following the injection, the patient may notice temporary floaters or a small bubble in their vision, which is the medication dissolving. Because Avastin’s effect is temporary, often lasting only a few weeks, patients require a series of serial injections, frequently on a monthly or bi-monthly basis, to control the underlying condition and maintain vision.
Understanding Risks and Monitoring
While the procedure is common and generally safe, patients should be aware of expected temporary effects and rare, serious complications. Common, mild side effects experienced immediately after the injection include temporary eye redness, grittiness or foreign body sensation, and small floaters. These effects typically resolve within a few days and are managed with simple post-procedure instructions, such as resting the eyes and avoiding rubbing.
A frequent occurrence is a temporary rise in intraocular pressure immediately following the injection due to the small volume of fluid added to the eye. Rare but serious complications require immediate medical attention. The most severe is endophthalmitis, a serious internal eye infection that occurs in about 1 in 1,000 injections. Other rare risks include retinal detachment and vitreous hemorrhage.
To manage these risks, follow-up monitoring is mandatory. Patients are instructed to contact their ophthalmologist immediately if they experience severe pain, worsening vision, increased light sensitivity, or persistent redness days after the procedure. Regular monitoring ensures that any potential complications or lack of response to the medication are detected and managed promptly.