A new study has shown that older people who have cataract surgery to improve their eyesight are less likely to develop dementia. Cataracts involve the lens of the eye becoming more cloudy with age, and they are one of the most common causes of vision loss in the elderly. The problem can be fixed by surgically removing the lens and replacing it with a plastic one. The reason that this is connected to lower incidence of dementia is not clear. It could be because better eyesight gives people the opportunity for more mental stimulation. Alternatively, it may be related to a strange effect that cataracts have on the colours that reach the retina at the back of the eye.



Dr Cecilia Lee of the University of Washington (US) conducted the study which looked at over 3,000 patients. She said, “The surgery clearly lowers the risk of dementia. This may happen because higher quality sensory input to the retina improves stimulus to the brain”. The other possibility stems from the fact that cataracts filter out blue light. This disrupts cells in the eye which help to govern our normal circadian rhythm – a condition which has previously been linked to dementia. “Cataract surgery may restore the blue light to reactivate those cells, and thus protect against cognitive decline,” says Lee. “There is much that we do not know yet.”