Ranibizumab is a prescribed medication administered by intraocular injection to treat specific conditions affecting the retina, the light-sensitive tissue at the back of the eye. Marketed as Lucentis, it is a therapy that manages diseases that can lead to vision loss if not addressed. The medication is prepared and delivered in a clinical setting by an ophthalmologist specializing in retinal diseases.
Mechanism of Action
Many sight-threatening retinal conditions are driven by a protein called Vascular Endothelial Growth Factor, or VEGF. In a healthy eye, VEGF functions in the normal maintenance of blood vessels. However, in certain diseases, an excess amount of this protein triggers the growth of new, abnormal blood vessels that are weak and leak fluid and blood into the retina. This leakage causes swelling and damage to the macula, the part of the retina responsible for sharp, central vision.
Ranibizumab is classified as an anti-VEGF therapy. It works by targeting and inhibiting the VEGF-A protein. The medication is a recombinant humanized monoclonal antibody fragment, which is a piece of a specially designed antibody that binds directly to the VEGF-A molecules in the eye. By attaching to VEGF, ranibizumab prevents the protein from signaling for the formation of these destructive new blood vessels and reduces their permeability. This action helps to stop leakage, decrease retinal swelling, and slow the progression of vision loss.
Following an injection into the vitreous cavity of the eye, the medication rapidly penetrates the retinal layers to reach its target. This targeted delivery allows the drug to act directly where it is needed while minimizing exposure to the rest of the body.
Conditions Treated
Ranibizumab is approved to treat several retinal diseases rooted in abnormal blood vessel growth and leakage.
- Neovascular or “wet” age-related macular degeneration (AMD), where new, fragile blood vessels grow under the macula in a process called choroidal neovascularization (CNV), leading to rapid central vision loss.
- Diabetic macular edema (DME), a complication of diabetes where damaged retinal blood vessels leak fluid into the macula. This swelling thickens the macula and impairs clear vision.
- Macular edema following retinal vein occlusion (RVO), where a blockage of a retinal vein leads to a backup of pressure, causing fluid and blood to leak into the macula.
- Myopic choroidal neovascularization (mCNV), which occurs in individuals with severe nearsightedness. The elongated shape of the eyeball can cause cracks beneath the retina, allowing abnormal blood vessels to grow and leak.
The Administration Process
The prospect of an eye injection can cause apprehension, but the process is carefully managed to ensure patient comfort and safety. Before the procedure, the eye is prepared with anesthetic drops to numb its surface. The pupil may also be dilated to give the doctor a better view of the back of the eye, and these steps ensure the patient feels little to no pain.
During the procedure, the area around the eye is thoroughly cleaned with an antiseptic solution to prevent infection. An instrument called an eyelid speculum is then gently placed to hold the eyelids open, preventing blinking. The ophthalmologist then performs the injection, which involves a very fine needle inserted through the sclera, the white part of the eye. The injection itself is very quick, lasting only a few seconds, and patients report feeling a sense of pressure rather than sharp pain.
After the injection, it is common to experience some temporary and mild sensations, such as a gritty or foreign body sensation, slight redness, or watery eyes. Many patients also notice new floaters in their vision, which may appear as small dots or bubbles. These are often tiny air bubbles from the injection or the medication itself and resolve within a day or two. The doctor will provide antibiotic eye drops to use for a few days post-procedure to minimize the risk of infection. Patients are advised to avoid rubbing their eyes but can resume most normal activities shortly after the appointment.
Potential Side Effects and Risks
Following a ranibizumab injection, some side effects are common and not a cause for alarm. Frequently reported reactions include mild eye pain or discomfort, conjunctival hemorrhage (a small, bright red spot on the white of the eye), and the appearance of vitreous floaters. Increased eye pressure is also a known side effect, and the doctor will monitor this before and after the injection. These issues are temporary and resolve on their own as the eye recovers.
While the majority of injections are performed without issue, there are rare but serious risks that require immediate medical attention. One of the most significant is endophthalmitis, a severe infection inside the eye. Symptoms of endophthalmitis include significant, worsening eye pain, increased redness, swelling of the eyelid, and decreased vision.
Other serious but infrequent complications include retinal detachment and iatrogenic traumatic cataract. A retinal detachment may present with symptoms like a sudden increase in floaters, flashes of light, or the appearance of a dark curtain moving across your vision. Any of these warning signs should prompt an immediate call to the ophthalmologist. Although there is a potential risk for arterial thromboembolic events, such as nonfatal strokes, clinical trials have shown this rate to be low.
Comparison with Other Anti-VEGF Treatments
Ranibizumab is one of several anti-VEGF medications available for treating retinal conditions. Patients may also hear about aflibercept (marketed as Eylea) and bevacizumab (marketed as Avastin). All three drugs work by inhibiting VEGF, but there are differences between them that influence a doctor’s recommendation for a patient.
Bevacizumab was originally developed as a cancer treatment and its use in eye care is considered “off-label,” though it is widely used and has been studied extensively for this purpose. A primary advantage of bevacizumab is its significantly lower cost compared to the other options. Aflibercept may bind to the VEGF protein more tightly and also targets another protein called Placental Growth Factor (PlGF). For some patients, this might allow for a less frequent injection schedule compared to ranibizumab or bevacizumab after an initial series of treatments.
All three medications have been shown to be effective in managing these retinal diseases and improving vision compared to no treatment. Studies comparing the drugs have found that while there can be subtle differences in outcomes, all are safe and effective choices. A retinal specialist will consider clinical findings, medical history, and treatment response when deciding which agent is most appropriate.