Wet or neovascular Macular Degeneration (AMD) is one of the most common causes for severe loss of vision. Wet AMD is responsible for 10-20% of all cases of AMD yet it accounts for 75% of the vision loss associated with AMD.
In the past treatment for Macular Degeneration consisted of using laser therapy to burn parts of the retina to save the remaining vision. The small blood vessels of the retina that grow in response to AMD are not like other blood vessels. They grow in response to the retina sending out signals that it is starving for oxygen. A factor called Vascular Endothelial Growth Factor (VEGF) causes new, small, leaky blood vessels to grow in the retina. These leaky vessels do more harm than good and cause more damage to the retina. The newest and most promising treatments involve blocking VEGF to stop the eye from producing new vessels.
Laser Photocoagulation
The oldest form of treatment started in the 1970′s and involved using a so called “hot” laser to burn the retina and its growth of new vessels to try and halt progression. The amount of vision saved was often moderate at best. After 5 years it was not uncommon for a treated patient to lose 5 lines of vision whereas an untreated patient lost 7 lines. Treatment did not guarantee against recurrence of new blood vessels. Recurrence is most likely to occur within the first 6-12 months after treatment.
Photodynamic Therapy (PDT)
While still being a laser treatment, PDT is more targeted for the blood vessels that cause the problem. The older photocoagulation burned everything it came in contact with, healthy retina as well as neovascular tissue. PDT involves using an injected photosensitizing chemical that is activated in response to certain wavelengths of light, in this case the laser used for treatment. It has an affinity for the blood vessels causing the damage and result in less collateral damage to surrounding tissue. It is sometimes referred to as a “cold” laser, even though destruction of tissue is still happening. Recurrence is again common with PDT therapy. An average patient will need 2-3 treatments their first year and 1-2 treatments the following year.
Anti-VEGF Drugs
Tumors thrive in an environment where they have access to a lot of blood. They need the constant source of nutrients to grow and replicate. The vessels of tumors release the same growth factor that the retina does. Some very bright doctors decided to try injecting the same anti-VEGF drugs that were used to fight cancer into the eye to fight wet AMD. The current therapy for AMD involves monthly injections of an anti-VEGF drug like Avastin or Macugen. AMD will progress without the consistent injections. However the benefits are much greater than with laser therapy. It is not uncommon for vision to actually increase a line or two instead of merely losing less lines than with no therapy at all.