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Bio Technology : July 2009
AusBioFEATURE Biotechnology advances for age-related vision loss By Dr Vicky Vallas, Director of Scribblers Inc Macular degeneration accounts for 48% of severe vision loss. It is the primary cause of blindness in Australia, mostly affecting people over 50. Newer treatments can slow the progression of the disease, but it is the bionic eye that will offer a way to improve sight. The Federal Government is set to inject $50.7m towards commercialisation of the bionic eye. Age-related Macular Degeneration (AMD) is caused by damage to the photoreceptors in the centre of the retina, leading to central vision loss. There are two forms of AMD. Non-exudative (“dry”) AMD is more common, representing 80–90% of cases. Dry AMD results from atrophy of cells behind the retina and is characterised by yellow deposits. Exudative (“wet”) AMD is a neovascular disease. Vision loss is caused by abnormal growth of blood vessels that bleed and leak to cause scarring and permanent damage to photoreceptors. Potential therapies for AMD Until recently, wet and dry AMD could not be effectively treated. Like many diseases of aging, a healthy diet and cessation of smoking are recommended. Promising research in Australia and overseas is advancing treatments to slow progression of disease and restore vision. Therapy for wet AMD includes Lucentis, an anti-vascular endothelial growth factor (anti-VEGF) monoclonal antibody fragment. Trials have shown that at least seven out of ten patients maintain their vision or notice improvement. It works by stopping the growth of blood vessels and hence the scarring that results in vision loss. Another potential biopharmaceutical is Avastin, the anti-VEGF monoclonal antibody upon which Lucentis is based. Treatment with these agents involves painful injections of antibody into the eye at up to monthly intervals. Research (including gene therapy) is progressing into less invasive ways to deliver anti-angiogenic agents. Research in the UK uses human embryonic stem cells to derive photoreceptor-like cells for injection into the retina. Clinical trials in humans are due within two years. Surgeons predict the treatment will become a routine one-hour procedure and expect it to be available within seven years. Another approach is transplantation of retinal tissue, but this has the problem of tissue availability. The bionic eye The bionic eye represents an ability to restore vision. The retinal prostheses consist of a microchip containing an array of electrodes. These act as artificial photoreceptors and are implanted into the retina. A camera mounted on spectacles collects images. They are transmitted to a processor that converts the images into a grid of electrical signals. This data is then sent by wireless transmission to the retinal implant. Bionic Vision Australia has an advanced prototype containing 98 electrodes. This model will allow recipients to detect light from dark and to navigate around large objects. It should be ready for human implantation by 2011. The second design, with more than 1000 electrodes, will provide the ability to recognise faces, to read large text and will restore functional central vision. It should be available in 2013. US researchers are currently implanting their prototype devices into patients. Volume 19 • Number 2 • July 2009 Australasian BioTechnology 27