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No human function lasts forever. The progressive and inevitable decay of both sight and hearing, perhaps the two noblest human senses, is a good example of how the insults of time affect us all, in spite of modern medical advances. Research groups throughout the world are continually searching for ways to extend the average lifespan, allowing humans to live even well beyond the age of 100. This scientifically aided extension of life is not without consequences, especially if the natural deterioration processes underlying different human organs are not seriously considered. The sense of vision serves as a good example of this. It has been calculated, based on both histological (counting the optic nerve axons) and functional (data from different perimetric techniques) studies,1–8 that every human being loses on average approximately 5000 to 9000 optic nerve fibres per year (fig 1). Progressive retinal nerve fibre layer thinning has also been shown with modern imaging techniques.9 10 Considering that a normal optic nerve is composed of one million to one and a half million optic fibres, upon reaching the hypothetical age of 200 a very limited number of retinal ganglion cells and nerve fibres would remain. This would probably lead to a condition of “physiological” blindness, unless truly effective neuroprotective …
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