Intravitreal Anti Vascular Endothelial Growth Factor (VEGF) therapy
Age-related macular degeneration (AMD) is the leading cause of blindness in people over 50 years of age. There are two types of macular degeneration: dry and wet. In the “wet” form of AMD, abnormal blood vessels grow in the back of the eye. Sometimes these vessels leak blood or fluid that causes blurred or distorted vision. Without treatment, vision loss may be quick and severe.
There are other eye conditions that cause loss of vision due to abnormal growth of blood vessels in the back of the eye. These can occur even in young patients, and include, but are not limited to, conditions such as high myopia (nearsightedness), histoplasmosis, angioid streaks, and eye injury. Sometimes there is no known reason for the abnormal blood vessels. Without treatment, vision loss may be quick and severe.
Refractory macular edema, or swelling around the macula, is edema that affects vision but does not respond adequately to the usual treatment methods. It can occur with conditions such as central retinal vein occlusion and diabetic retinopathy. Without effective treatment, vision loss could progress and become permanent.
Types of Anti VEGF agents
Lucentis (ranibizumab) is a humanized anti-VEGF antibody fragment that inhibits VEGF activity by competitively binding with VEGF. The Food and Drug Administration (FDA) has approved Lucentis treatment for wet macular degeneration patients.
About 95% patients with wet macular degeneration maintain their baseline vision after 12 months of treatment with Lucentis. The vision loss, if any, is less than 15 letters of visual acuity. This level of vision loss is considered to be not clinically significant. This is an important treatment effect because to date all other available treatment options at best delay the inevitable vision loss but do not prevent ongoing vision loss. The results from Lucentis clinical trials support its use to prevent further vision loss from wet macular degeneration.
About one-third patients gain vision after 12 months of treatment with Lucentis. This vision gain is clinically significant - defined as gaining more than 15 letters of visual acuity. This is perhaps the most significant reason for initiating Lucentis treatment in wet macular degeneration. The vision gain after Lucentis treatment enables the patients to doing things like reading again, however not everyone will get such a positive outcome. There is no other macular degeneration treatment that has been shown to improve vision in the settings of a FDA controlled clinical trial.
- Long term data is not available to fully assess the effects of Lucentis.
Macugen (Pegaptanib) is a selective Vascular Endothelial Growth Factor (VEGF) antagonist to VEGF isoform 165. Macugen blocks VEGF actions and prevents the growth of abnormal new vessels and prevents leakage of fluid and blood in the retina. Macugen was approved by the FDA for use in wet macular degeneration in December 2004. The recommended dose of Macugen is 0.3 mg of intravitreous injection administered once every 6 weeks. In the clinical trials, after 1 year, 45% eyes developed moderate vision loss and 22% developed severe vision loss if no treatment was given. If treated with Macugen, the probability of developing moderate vision loss over a period of 1 year is reduced by about 15% and the probability of developing severe vision loss is reduced by about 50%. This implies that the rate of vision decline with Macugen treatment is slower than the rate in patients who do not receive macugen treatment.
Avastin TMwas not initially developed to treat eye conditions. Based upon the results of clinical trials that demonstrated its safety and effectiveness, Avastin TM was approved by the Food and Drug Administration (FDA) for the treatment of metastatic colorectal cancer. As a condition of approval, the manufacturer produced a “label” explaining the indications, risks, and benefits. Ophthalmologists are using Avastin TM “off-label” to treat AMD and similar conditions since research indicates that VEGF is one of the causes for the growth of the abnormal vessels that cause these conditions. Some patients treated with Avastin TMhad less fluid and more normal-appearing maculas, and their vision improved. Avastin TM is also used, therefore, to treat macular edema, or swelling of the macula
Possible complications and side effects of the procedure and administration of Anti VEGF therapyinclude but are not limited to retinal detachment, cataract formation (clouding of the lens of the eye), glaucoma (increased pressure in the eye), hypotony (reduced pressure in the eye), damage to the retina or cornea (structures of the eye), and bleeding. There is also the possibility of an eye infection (endophthalmitis). Any of these rare complications may lead to severe, permanent loss of vision.