27 Jan Avastin: An Adjunctive Therapy for Proliferative Diabetic Retinopathy
Avastin® is useful for a variety of eye conditions; it is principally used to treat wet macular degeneration and is becoming a popular option to treat diabetic macular edema. On occasion, Avastin has also been useful, in my practice, to treat patients with proliferative diabetic retinopathy.
VEGF (Vascular Endothelial Growth Factor) also causes abnormal blood vessels to grow in cases of “wet” macular degeneration and … proliferative diabetic retinopathy.
Proliferative Diabetic Retinopathy (PDR) is defined by the presence of abnormal “neovascularization.” These are abnormal proliferations of blood vessels that grow inside the eye. In patients with diabetic retinopathy, the VEGF is produced in response retinal ischemia; retinal demand for oxygen exceeds the supply due to poor blood supply. VEGF then causes neovascularization to develop. This neovascularization can cause blindness by causing retinal detachments or neovascular glaucoma.
The traditional treatment for proliferative diabetic retinopathy has been laser photocoagulation. The laser treatment, called pan-retinal photocoagulation (PRP), has been the treatment of choice for years. The PRP destroys enough tissue so that the available blood supply is adequate to meet the oxygen requirements of the tissue. When this occurs the “ischemia” is cured, VEGF is no longer produced and the proliferative retinopathy becomes stable.
Occasionally, I have patients that do not respond well, or completely, to pan-retinal photocoagulation. Lately, on select cases, I have used Avastin as an alternative to pan-retinal photocoagulation for the treatment of proliferative diabetic retinopathy.
So far the treatment works well. The neovascular tissue regresses quickly and I recheck patients every 4-6 weeks. The injections do need to be repeated.
What Does This Mean? Pan-retinal Photocoagulation has been the gold-standard for the treatment of proliferative diabetic retinopathy. The PRP can decrease light to dark adapatation, that is, it takes awhile to get used to light when coming out of a movie theater. It is a difficult procedure to perform, but has been very effective over the years. I consider it a good “fix.”
An alternative therapy is welcomed for two reasons. Avastin injections are certainly easier to perform and seem not too affect the vision. Avastin also treats the disease by a different mechanism and may increase the chances of achieving stability. On the other hand, Avastin does NOT change the relative ischemia in the retina, that is, the oxygen demand is still greater than oxygen supply. It may be less of a permanent “fix.”