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Investigational Treatments
There are various therapies, still under investigation, used in treating ARMD. Discussion with your ophthalmologist is highly recommended before turning to these investigational treatments.
Nonexudative
PTAMD - "Prophylactic treatment of Age-Related Macular Degeneration". This multicentre clinical control trial is based on a pilot study called CAPT - "Complications of AMD Prevention Trial". In the pilot study, improvement in visual acuity and reduction in drusen were noticed with treatment from light treatment with an infrared laser.
Rheopheresis - This treatment is based on blood filtration. The proposed mechanism of action is that the removal of certain proteins and lipids allows for a reduction of the blood viscosity; improvement of capillary blood flow, improved endothelial cell function and enhancement of choriocapillary perfusion. Each of these is thought to lead to improved photoreceptor function, resulting in better vision. MIRA-1 is a multi-centre clinical trial of this procedure, and is still enrolling patients. Presently only US sites are involved.
Exudative
Anti-Angiogenesis
- Thalidomide - This drug, once used for nausea in pregnant mothers and remembered for the children with malformed limbs it created, is being reinvestigated. It appears that this drug reduces the growth of new blood vessels. Various studies are now being conducted to see if it is beneficial in the wet form of ARMD. A known side effect is the development of a nerve conduction problem in approximately 25% of patients.
- PKC 412 - Is one of the new classes of drugs that stop new blood vessel growth. Recruitment trials are to begin at the Wilmer Eye Institute at Johns Hopkins University in Baltimore.
Radiation - Theoretically, closure of a CNVM may occur by precisely localizing the radiation beams. The side effect is the unknown risk in the future to the surrounding tissue, including the brain. A randomized multicentre clinical control study provided evidence that radiation treatment showed no benefit as a treatment for subfoveal CNVM secondary to ARMD at 1 year. (Ophthalmology 1999 Dec;106(12):2239-47)
Submacular Surgery - In this type of surgery, a hole is made in the retina and the CNVM is grasped with tiny forceps and removed. In some situations it may be effective, but the long-term results are not promising in ARMD compared to CNVM in other diseases. There is a major rate of reoccurrence. In addition, complications of surgery are possible, including infection, bleeding and retinal detachment. A multicentre clinical trial is presently reviewing the success rate of this procedure.
Macular Translocation - This surgical procedure essentially consists of detaching the retina from the RPE and rotating the macular retinal tissue to healthy RPE. A gas bubble is used to hold the retina in place until a natural seal is reestablished. The gas disappears in several weeks. Conventional laser is applied, usually through the bubble to destroy the CNVM; however, since the fovea has been moved, damage to non-foveal areas occurs. The result is a preservation of the vision from the fovea. The procedure holds promise, but multiple complications may occur, including infection, bleeding, retinal detachment, and misalignment of the eyes. The type of misalignment is seen as a tilt in the vision by the patient. Patients may compensate with a head tilt and may require other procedures to rectify this. Only certain patients qualify due to the risks.
Gene Therapy - VEGF (Vascular Endothelial Growth Factor) is one of the series of growth factors that strongly stimulates new blood vessel growth (angiogenesis). VEGF gene therapy is being used in patients with blockages in the heart and leg vessels. For ARMD, an antibody to this growth factor is required - i.e. an anti-VEGF. Present work is looking into this. There is much promise in this technology.
RPE transplantation - Theoretically, replacing the damaged RPE may stop or reverse the disease process. The problem is where to obtain RPE cells and how to implant them. Presently, RPE from aborted fetuses are used. Implantation is also a problem, as RPE cells have a top and bottom. The present technology is unable to implant all these cells in the proper orientation. Furthermore, rejection of the tissue is of concern.
Artificial Retina - Someday it may be possible for technology to produce an artificial retina or eye for everyday human use but this development is a long road away. Preliminary research is looking into implanting light-sensitive chips.
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