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Old and New Treatments for Macular Degeneration

Until recently the only available treatment to seal these leaking blood vessels was with a laser. The earliest treatment was Laser Photocoagulation. This was followed by Photodynamic Therapy (PDT) with Visudyne™ (a drug injected intravenously and used to help direct the laser to the affected area) and was not suitable for all types of lesions. The blood vessels may again begin to leak and further treatment may be required. The laser treatment itself may cause scarring. Researchers and physicians have looked for a follow-up to this treatment that might maintain vision for a longer period of time without repeated laser use. They are also looking for new therapies which would be effective for all types of wet AMD.

One line of thought stems from cancer research and the causes of angiogenesis—the growth of new blood vessels. It was discovered that there is a protein in the eye which encourages the development of blood vessels called "vascular endothelial growth factor" (VEGF) and drugs are being developed to inhibit VEGF by trapping it or preventing it from binding with elements which will stimulate growth. Chemically synthesized short strands of RNA (nucleic acid) called "aptamers" prevent the binding of VEGF to its receptor.

Presently three types of VEGF inhibitors are in use: Macugen, Lucentis and Avastin. All are given by intraocular injection. A number of injections must be given over an extended period of time. If treatment commences early in the development of the disease, positive results have been shown in slowing progression and in some cases, improving visual acuity. Side effects of intravetreal injections may include:

Serious eye infection that may include eye pain, light sensitivity, vision changes.

Increased eye pressure

Retinal detachment

Vitreous floaters

Consult with your retinal specialist to make certain you understand what all the side effects might be.

Laser Photocoagulation

Between 1979 and 1994, the Macular Photocoagulation Study Group conducted a number of clinical trials that enrolled patients with CNV lesions (Choroidal Neovascularization) in one or both eyes. Each affected eye was randomly assigned to either laser treatment or observation. For eligible eyes with CNV in extrafoveal, juxtafoveal and subfoveal locations, laser treatment reduced the risk of severe visual loss.

There are three major limitations of laser photocoagulation treatments. First, not more than 10-15% of CNV lesions are small enough and sufficiently delineated by fluorescent angiography to be eligible for laser treatment. Second, even if laser treatment is initially successful, there is at least 50% chance that leakage will recur during the next two years. Many such recurrences are amenable to additional treatment if detected early, which means that patients need careful monitoring after the first treatment. Finally, at least half of patients post-treatment with sufficiently well-circumscribed CNV lesions still have some leakage beneath the center of the fovea. Laser treatment leads to immediate reduction in central vision in these patients with leakages, but with sufficient follow up, the extent of visual loss is less in laser treated eyes than in untreated eyes. These existing laser therapies are limited in their effectiveness and may also lead to scarring of the macula and additional vision loss.

Photodynamic Therapy with Visudyne™

During April 2000, the FDA approved a new treatment, Photodynamic Laser Therapy, which uses a light-activated drug called Visudyne™(verteporfin for injection). Visudyne™ therapy is a two-step procedure that can be performed in a doctor's office. First, Visudyne™ is injected intravenously into the patient’s arm. The drug is then activated by shining non-thermal laser light into the patient’s eye. Visudyne™ therapy involves the use of a specifically-designed laser that produces the low-level, non-thermal light required to activate the drug which results in a selective destruction of the unwanted leaking vessels. The procedure seals off leaking vessels while leaving healthy ones intact and is believed to be a major improvement over previous laser treatments. In one large clinical trial, photodynamic therapy with Visudyne™ photosensitizer delayed or prevented loss of vision during at least one year follow up in patients with predominantly classic CNV lesions. Unfortunately, even the most successful treatments do not preclude reoccurrence, making multiple treatments likely. However, the rate of vision loss may be slowed down and some sight may be preserved. It is important to understand that this drug is not a cure. At best it preserves the status quo: It will not restore vision that has already been lost.