An intravitreal injection (IVI) delivers medication directly into the vitreous humor, the clear, gel-like substance filling the center of the eye. This targeted delivery method ensures a high concentration of the drug reaches the retina and underlying tissues, where many vision-threatening diseases originate. The ability to bypass the eye’s natural barriers makes the IVI an effective treatment for conditions affecting the back of the eye. The procedure is quick, performed in an outpatient setting, and is considered a standard and safe practice by retina specialists.
Eye Conditions Requiring Treatment
Intravitreal injections are primarily used to treat retinal diseases that cause fluid leakage, swelling, or the growth of abnormal blood vessels. The most common conditions requiring this therapy are wet age-related macular degeneration (AMD), diabetic retinopathy, and retinal vein occlusions (RVO). These diseases often lead to vision loss by damaging the macula, the part of the retina responsible for sharp, central vision.
Wet AMD is characterized by the formation of fragile, new blood vessels beneath the retina, which leak fluid and blood, causing scar tissue and rapid vision deterioration. Similarly, diabetic retinopathy, particularly diabetic macular edema (DME), involves damaged blood vessels that leak fluid into the macula due to high blood sugar levels. RVO occurs when a vein in the retina is blocked, leading to hemorrhage and fluid buildup in the macula.
The medications delivered via IVI work to counteract these damaging processes. The most frequently used class of drugs is anti-vascular endothelial growth factor (anti-VEGF) agents. Anti-VEGF drugs block this protein, which stimulates the growth of problematic, leaky blood vessels, helping to stop vessel growth, reduce swelling, and decrease fluid leakage.
Corticosteroids are another type of medication used in IVIs, often for persistent swelling or inflammation, such as certain forms of DME, RVO, or uveitis. These steroid compounds modulate the inflammatory response within the eye, helping to decrease macular edema. A combination of anti-VEGF and corticosteroid treatment is sometimes employed for patients who do not respond sufficiently to anti-VEGF monotherapy.
The Intravitreal Injection Procedure
The process is performed in a doctor’s office and takes about 10 to 15 minutes, with the injection itself lasting only a few seconds. Preparation begins with the administration of anesthetic drops or gel to numb the surface of the eye. This topical anesthesia ensures that the patient feels only pressure, rather than pain, during the actual injection.
Next, an antiseptic solution, typically povidone-iodine, is applied to the eye and surrounding eyelids to sterilize the area and minimize the risk of infection. A small instrument called an eyelid speculum is then gently placed to keep the eyelids open and prevent blinking.
The retina specialist will ask the patient to look in a specific direction to expose the injection site, which is typically in the pars plana, the white part of the eye surrounding the iris. The medication is then injected using a very fine needle, approximately 3.5 to 4.0 millimeters from the limbus (the border between the cornea and the sclera). Patients commonly report feeling a brief sensation of pressure.
Immediately following the injection, the speculum is removed, and the eye is cleaned. The doctor may check the intraocular pressure (IOP) because the injected fluid causes a temporary rise in pressure that usually returns to normal within minutes. Antibiotic drops may be administered before the patient is released.
Recovery and Potential Side Effects
After the injection, patients can expect a few common, temporary symptoms as the anesthesia wears off. It is normal to experience a gritty, mildly scratchy, or irritated feeling in the treated eye for a few hours, often a reaction to the antiseptic solution used. Patients may also notice small black spots, bubbles, or floaters in their vision that represent the medication or tiny air bubbles dispersing in the vitreous humor.
A small, red spot of blood, known as a subconjunctival hemorrhage, may appear on the white part of the eye at the injection site. This is harmless and generally resolves on its own within about a week. Lubricating artificial tears can be used to alleviate the mild discomfort and dryness. To prevent contamination, patients are advised to avoid rubbing the eye, wearing contact lenses, or swimming for a couple of days post-injection.
While rare, be aware of the signs of more serious complications that require immediate medical attention. Symptoms such as severe, persistent eye pain, sudden decrease in vision, or increasing redness and discharge could indicate a serious issue like an infection, known as endophthalmitis. Other rare complications include a retinal detachment, which might manifest as new floaters, flashes of light, or a dark curtain obstructing vision. Contacting the retina specialist immediately upon noticing any of these severe signs is crucial for protecting vision.