As the name implies, intravitreal injections are injections of medication into the vitreous — the gel that fills the back portion of the eye. A variety of medications can be injected in this manner. Below is a description of the most commonly injected medications.
Severe infection can arise inside the eye. This condition is known as endophthalmitis. Although it is rare, it can cause severe visual loss. It is encountered most often after severe eye injuries, cataract surgery and intravitreal injections of medications like Avastin, Lucentis and triamcinolone. Endophthalmitis is most often caused by bacteria but is occasionally due to fungi. Antibiotics (medications that kill bacteria) are injected into the vitreous to treat bacterial endophthalmitis. The antibiotics most commonly injected are vancomycin and ceftazidime. They are often injected together, because this combination of antibiotics is able to effectively treat nearly all intraocular infections.
Avastin is a medication that is injected into the vitreous of the eye for treatment of a number of disorders, including “wet” macular degeneration, retinal swelling and abnormal blood vessel growth due to diabetic retinopathy, and blockages of retinal veins. Avastin was developed and FDA-approved for the treatment of metastatic colon cancer but is used very frequently in the treatment of eye diseases. It is usually injected about every six weeks when treatment is initiated, and the interval between injections is often lengthened gradually. Because the effect of Avastin declines over time, it often has to be injected indefinitely in order to maintain its beneficial effect on the vision.
Lucentis, like Avastin, is injected into the vitreous of the eye for treatment of a number of disorders, including “wet” macular degeneration, retinal swelling and abnormal blood vessel growth due to diabetic retinopathy, and blockages of retinal veins. It was developed and FDA-approved initially for treatment of “wet” macular degeneration but has also recently been FDA-approved for treatment of branch retinal vein occlusions and central retinal vein occlusions. It may eventually become FDA-approved for treatment of diabetic retinopathy.
Eylea is also injected into the vitreous and inhibits growth of abnormal blood vessels behind the retina in patients with wet macular degeneration and reduces retinal swelling in patients with central retinal vein occlusions and diabetic macular edema, like Avastin and Lucentis, but it works through a different mechanism. It seems to improve and maintain vision at least as well as Avastin and Lucentis and its duration of action seems to be longer. Because of its longer duration of action, it may be able to reduce the burden of treatment for macular degeneration and central retinal vein occlusions on both patients and doctors alike.
Jetrea is a medication that dissolves the connection between the vitreous gel and the retina. It is used to treat symptomatic vitreomacular adhesion, in which the vitreous gel is abnormally adherent to the central retina (macula). The macula often becomes swollen, resulting in visual loss. By relieving the adhesion between the vitreous and the macula, the swelling can often be reduced or eliminated and the vision often improves. Jetrea is injected into the vitreous of the eye, a procedure that can be performed in the office. Symptomatic vitreomacular adhesion has traditionally been managed with vitrectomy, but Jetrea allows the patient to avoid the risk and expense of vitrectomy. Macular holes are thought to be the result of abnormal vitreomacular adhesion, as well, and can also be treated with Jetrea, although the success rate in closing macular holes with Jetrea is substantially less with Jetrea (about 40%) than with vitrectomy (about 90%).
Triamcinolone is a corticosteroid — a type of medication most known for its ability to reduce inflammation. Inflammation develops when the body’s immune system is overly active. Prednisone is the most well-known corticosteroid. It is taken by mouth for a variety of inflammatory diseases. Triamcinolone can be injected into the vitreous to reduce inflammation in the eye (also known as uveitis), but it can also be used to reduce swelling in the retina (also known as macular edema). Common causes of macular edema for which triamcinolone is sometimes injected into the vitreous include diabetic retinopathy, retinal vein occlusions and cystoid macular edema. The main side effects of triamcinolone are glaucoma (elevated eye pressure) and cataracts. There is approximately a 30% chance of glaucoma with intravitreal triamcinolone injections. Cataracts are accelerated in most patients who receive intravitreal triamcinolone injections, but they usually develop quite gradually.
The Ozurdex implant consists of dexamethasone, a corticosteroid like triamcinolone. It slowly dissolves in the vitreous, exerting its therapeutic effect over several months. It is currently FDA-approved for uveitis (inflammation in the eye), retinal vein occlusions and diabetic macular edema. Like triamcinolone, Ozurdex can cause elevation of the eye pressure and progression of cataracts.