The phrase “eye stroke” has recently appeared in news reports about a very rare side-effect of weight-loss injections. It’s not a formal medical diagnosis, but a shorthand used to describe a condition in which reduced blood flow damages the optic nerve and causes sudden vision loss.

The phrase might be misleading. Unlike a conventional stroke – which can cause someone to lose the ability to move their limbs or speak – an eye stroke can be harder to recognise at first. Vision can be lost entirely or partially, in one or both eyes, with no numbness or paralysis.

The word “stroke” is used because, as with the more familiar condition, the underlying cause is a loss of blood supply that leads to cell death and tissue damage. The correct medical term for an eye stroke is non-arteritic anterior ischaemic optic neuropathy (Naion).

The recent connection between Naion and weight-loss treatments has made headlines following a large study examining semaglutide, the active ingredient in several popular weight-loss drugs.

Researchers analyse more than 30 million side-effects reported to the US Food and Drug Administration and found that 31,774 involved semaglutide. One drug in particular stood out: Wegovy was found to have a far stronger association with Naion than other........

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