Exudative (Wet) Macular Degeneration
Although this accounts for only 10% of macular degeneration, it is responsible for the majority of legal blindness from the disease. It is characterized by a rapid visual loss as abnormal blood vessels grow underneath the retina and leak fluid and bleed. Over time, these vessels have associated scar tissue which can lead to permanent scar formation under the retina. Patients with dry macular degeneration have about a 1-5% chance per year of converting from the dry form to the wet form. Once wet macular degeneration has happened in one eye, the chance of it happening in the other is increased to approximately 5-10% per year.
Treatment
Although we have treatments for macular degeneration, it must be understood that these do not cure the disease or reverse visual loss in most cases. The goal of currently available treatments is to stop leakage, bleeding, and to limit the size of the blind spot to what it is. Generally, if exudative macular degeneration is left untreated, the blood vessels tend to grow which enlarges the blind spot, and the blood vessels continue to leak fluid and occasionally bleed. Scarring and permanent damage generally occurs to some extent in most patients.
Thermal Laser
Thermal laser uses a laser to burn and coagulate blood vessels under the retinas. Drops are used to anesthetize the eye and the laser is used to burn the vessels. The advantage of this technique is that it has been around for many years and is relatively easy on the patient. It does not impose any restrictions post-operatively. The primary disadvantage is that the overlying retina is also burned and coagulated in the process. This is generally reserved for well-defined vessels that are present in areas away from the fovea. Because the inciting cause of the blood vessel growth is not cured by the laser, there is up to a 50% recurrence rate. However, well-designed clinical studies show that patients' vision does better with treatment compared to without.
Photodynamic Therapy
This newer laser treatment uses a light-sensitizing dye injected into a vein to more selectively destroy the vessels and spare the overlying retinal tissue. This is generally used for vessels that involve the direct center of the retina or fovea. The dye, called verteporfin (Visudyne), is infused into the patient's arm over a ten minute period. Five minutes later a laser is used to treat the vessels for an 83 seconds. Because this photosensitizing dye is injected into a patient's vein, the dye travels throughout their body and there are strict restrictions to avoid direct sunlight for five days. Like thermal laser, this treatment does not eliminate the original cause of the vessel growth. On average, patients need approximately three treatments during the first year, two during the second, and one during the third. Patients are seen on an every three month basis with repeat Fluorescein Angiograms. If there is leakage on the angiogram, the laser treatment is repeated. In rare cases where both eyes are affected by these vessels, a treatment can be performed sequentially with the same dye infusion.
Photodynamic therapy (PDT) is an FDA-approved treatment for choroidal neovascularization (CNV) due to age-related macular degeneration (AMD). The primary study in this disease was called the TAP (Treatment of AMD with Photodynamic therapy) study. This was published in the journal Archives of Ophthalmology in 2001. The major results of the 2-year study are as follows:
Year 1 - 3.4 treatments
Year 2 - 2.2 treatments
What Side Effects Can Occur with PDT and Visudyne?
By far, most patients tolerate this procedure without any problems. The most common reported side effects (Visudyne vs. placebo) were visual disturbance (22% vs. 16%), back pain (2.5% vs. 0%), infusion-related problem (16% vs. 6%), photosensitivity (4% vs. 0%), and allergic reactions (2% vs. 4%).
The two most specific problems were back pain and photosensitivity. Back pain can be reduced by having patients drink a couple extra glasses of water before the procedure. Photosensitivity can be avoided by staying out of direct sunlight for the full 5 day period.
Pegaptanib Sodium (Macugen)
Pegaptanib sodium is the only FDA-approved anti-VEGF treatment at this time. It is administered by directly injection into the vitreous cavity every six weeks. Although most patients are initially hesitant, it is a quick and painless procedure that only requires topical and subconjunctival anesthesia. Currently, this is being evaluated as a maintenance therapy after initial control of the lesion by other treatments.
Triamcinolone Acetate (Kenalog)
Triamcinolone Acetate is a long-acting anti-inflammatory steroid which is used in wet macular degeneration for its action against blood vessel growth and retinal swelling. This is often used in conjunction with photodynamic therapy, and has been reported to be successful in improving vision in a European Clinical study. Althought this study used PDT followed by the Kenalog injection, we inject first and perform laser about one week later. In our experience, this works better than PDT alone.
Bevacizumab (Avastin)
Bevacizumab is an anti-VEGF antibody that was originally approved by the FDA for treatment of colorectal cancer. Through pioneering work at the Bascom Palmer Eye institute in Miami, Dr. Phil Rosenfeld and colleagues have shown this to be a very effective treatment for exudative macular degeneration.
Bevacizumab has dramatically improved outcomes in exudative macular degeneration. Because this is still considered an "off-label" use of the drug, it is not currently covered in Indiana by Medicare and most insurance carriers. It has however, been approved for covereage in some Eastern states, and it may eventually be covered here in Indiana.
Ranibizumab (Lucentis)
Ranibizumab is an anti-VEGF antibody that was derived from Bevacizumab and is expected to be approved by the FDA for treatment for exudative macular degeneration in the summer of 2006. Data from two clinical studies (MARINA and FOCUS) reported maintained and/or improved vision for most patients with wet AMD. It is anticipated that this will be administered by monthly intravitreal injections.
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