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Older people who have cataract surgery to improve their eyesight are less likely to develop dementia afterwards. From a report: The effect could be because people who lose their eyesight typically spend more time at home, and so get less mental stimulation -- or it could be down to a strange effect that cataracts have on the colours that reach the retina at the back of the eye. Cataracts, which involve the lens of the eye becoming more cloudy with age, are one of the most common causes of vision loss in older people. They can be fixed by surgically removing the lens to replace it with a plastic one. Sight loss was already known to be a risk factor for developing Alzheimer's disease and other forms of dementia. Cecilia Lee at the University of Washington in Seattle wondered whether cataract surgery would have a noticeable correlation with dementia incidence.