This is sadly another one of those ageing processes. If you imagine that the eye is filled with a cellophane bag full of jelly (the vitreous) – as we get older this degenerates and goes more liquid. Eventually the bag cannot hold itself up and collapses down. It is usually attached to the round optic nerve at the back of the eye (imagine with superglue) – as it pulls away and flops down and you can see the imprint of the “superglue” on the bag and that is the floater. It will persist and cannot be removed (well it can by radical surgery but we wouldn’t undertake that form of surgery for only the inconvenience of the floater). Slowly but surely the brain does adapt to it and begins to ignore it. You may only notice it against a bright or white background or on a very bright day. The more you ignore it the sooner it will not trouble you.
As the jelly comes away and peels off the retina it irritates it causing flashes of light – the retina has no touch or pain nerves and can only respond by light. In some people there are abnormal attachments between the retina and the jelly and when the jelly pulls away it can tug a bit of retina with it resulting in a tear. This can be closed with laser but if it is not picked up and treated then fluid can get underneath and peel the retina away – this would require an operation to stick it back down. It is usually short sighted people who tend to get this problem.
The great majority of people who have a posterior vitreous detachment have absolutely nothing to worry about. If you have flashes and/or floaters it is worth going to your optometrist for an examination after drops to make your pupils big. If they are concerned they can send you to the hospital eye service for a comprehensive examination.
It is prudent to remain vigilant as some people can still develop retinal problems. If you suddenly notice a new hail of tadpole-like floaters or any solid curtain coming across your peripheral vision you should report to the eye casualty immediately. It is extremely unlikely but worth watching out for.