Flashing lights can also be an early warning for migraines.'Flashing lights that last for 15 to 30 minutes are often symptomatic of ocular migraines, which are headaches that also cause coloured lights usually in both eyes,' he says.Floaters are a normal part of everyone's vision and usually nothing to worry about, says Dr Blakeney.'What you're actually seeing are shadows cast by rogue strands of collagen.
'If you stare at a n very bright light, such as the sun or a welding torch, for long enough, those images can burn into your retina, damaging your long- term sight , ' says Mr Constantine-Smith.
Floaters are harmless, but if they start to have a real impact on sight, they can be rectified with a vitrectomy.
Normally performed under a general anaesthetic, this replaces the vitrous jelly with saline solution. If the occasional floater turns into a sudden 'cobweb' of squiggles, especially with associated flashes, or one single, large floater that won't disappear.
But when people start losing their sight - most commonly due to age- related macular degeneration or sometimes glaucoma - their brains don't receive as many pictures and new fantasy pictures or old pictures stored in our brains are released and experienced as real objects.
'It's a condition known as Charles Bonnet Syndrome (CBS), named after the Swiss philosopher who noticed his blind grandfather having hallucinations of things that obviously weren't there,' says Mr Moriarty.
'This is a sign of vitreous detachment, where the vitreous jelly pulls away from the retina,' says Dr Blakeney.