Eye floaters: causes, treatment and when to get urgent help

For most people the answer is that treatment is not needed. Look After Your Eyes says that most of the time floaters are harmless and, although they can be annoying, treatment is not usually advised. The NHS says flashes may eventually stop and floaters often become less noticeable as you get used to them. If you have had floaters for years, your eye and your brain learn to ignore them.

The NHS says that if you have problems with floaters or flashes, your eyes will be checked at an opticians to see if you need to be seen by an eye doctor (ophthalmologist) for more tests or treatment. You will usually only need treatment if you have a problem that could affect your vision.

The one situation where treatment is urgent is a retinal tear or detachment. The NHS says you will be referred to hospital for surgery if tests show your retina may be detached or has started to come away, and that surgery will usually stop your vision getting worse. It may involve sealing the tear with laser or freezing treatment (cryotherapy), injecting a bubble of gas into the eye, attaching a band around the eye, or removing and replacing the jelly inside the eye (vitrectomy). It is usually done with local anaesthetic and you do not normally need to stay in hospital overnight.

The hollow space in the middle of the eyeball is filled by a clear, jelly-like substance called the vitreous. Moorfields Eye Hospital explains that as the vitreous ages it liquifies and becomes less firm, and strands of a protein called collagen become visible within it. Anything floating in the vitreous casts shadows onto the retina, the light-sensitive layer at the back of the eye, which is how you see floaters.

Look After Your Eyes says some people are born with floaters, but most develop as you get older, when the gel naturally shrinks. The gel separates into watery fluid and wavy collagen strands, which you see as line-shaped floaters. Sometimes the gel collapses away from the retina and you may see a large ring-shaped floater.

This separation is the posterior vitreous detachment (PVD). Moorfields says that in nearly all people, usually over the age of 40, the vitreous separates from the retina, and when it tugs on the retina it can cause flashes of bright white light and sometimes a sudden shower of floaters. Look After Your Eyes says PVD is very common and more likely as you get older. Floaters can also be caused by some inflammatory eye conditions, infection, eye disease or eye injury, which is not very common.

Moorfields describes floaters as shapes or shadows that people can see drifting across their vision, appearing as small dots or irregularly shaped strands. Look After Your Eyes says they can look like a hair or small pieces of cobweb, can be semi-transparent or dark, and move away in the direction you move your eye when you try to look at them.

You may only notice them when staring at a light-coloured surface or at the sky during the day. Floaters rarely cause problems with your vision, and some people find they are a nuisance but most get used to them.

Look After Your Eyes says that with a PVD you may see flashes of light in front of one eye, like small sparkles, lightning or fireworks, as the gel touches or tugs the retina. The flashes tend to be in the extreme corners of your vision, come and go, and do not obscure any part of it. You may notice them more when going from a light to a dark environment, and they may continue on and off for weeks or months.

It says these are different from the shimmering or zig-zag lines that may be part of a migraine aura. You can also get flashes after being hit in the eye or if you rub your eyes roughly.

The NHS says to ask for an urgent opticians appointment or get help from NHS 111 if you have floaters or flashes in your vision for the first time, you suddenly get floaters or flashes, the number of floaters or flashes suddenly increases, you have a dark curtain or shadow moving across your vision, you also have blurred vision, you also have eye pain, or floaters start after eye surgery or an eye injury.

These could be signs of a serious problem with the back of the eye, which the NHS says could permanently affect your vision if it is not treated quickly. For a detached retina, the NHS says you can get one more than once, so get medical help as soon as possible if symptoms come back.

Look After Your Eyes says floaters are more common in people who are short-sighted, may increase after an eye operation such as cataract surgery or laser treatment after it, and are more likely with a history of eye injury, infection or inflammation.

The same source lists the risk factors for retinal detachment: eye surgery such as cataract surgery, being short-sighted (with a prescription over -3.00D), an eye injury, a family history of retinal detachment, having had a detachment in either eye, being over 50, certain retinal diseases such as lattice degeneration, and conditions such as Marfan syndrome. The NHS adds that there is nothing you can do to prevent PVD, and it is not clear exactly why it leads to retinal detachment in some people.

Look After Your Eyes says an ophthalmologist or an optometrist will use eye drops and a special microscope to look inside your eyes to check whether your retina is damaged. The NHS says that if you have problems with floaters or flashes, your eyes will be checked at an opticians to see if you need to be seen by an eye doctor for more tests or treatment.

The NHS route for sudden floaters or flashes is an urgent opticians appointment or NHS 111, with onward referral to an eye casualty or hospital eye service if a tear or detachment is suspected. If you cannot reach an optometrist, Look After Your Eyes advises going to an eye casualty department, or A&E if there is none nearby.

Some people also arrange a private eye assessment. Because a retinal detachment can permanently affect vision if not treated quickly, do not wait for a routine appointment when the warning signs above appear.