Floaters and Flashes


Artist’s impression of floaters when looking at the sky

Floaters appear as black spots or something that looks like a hair or small pieces of cobweb. These can be semi-transparent or dark and appear to float in front of your vision. If you have had these for years, your eye and your brain learn to ignore them. Sometimes the number of floaters increases as you get older. Occasionally an increase in floaters can be a sign of problems inside the eye.

Because they ‘float’ in the jelly of your eye, you will find that if you move your eye to try to look at a floater it will move away in the direction you move your eye. You might only see the floater if you are staring at a light coloured surface or at the sky during the day.

Some people find that floaters can be a nuisance, but most people become used to them. They rarely cause problems with your vision.

Why do floaters occur?

Some people are born with floaters. Other floaters occur as you get older when the gel in the eye, the vitreous humour, naturally shrinks. The gel separates into a watery fluid and wavy collagen fibrils. The fibrils are seen as line-shaped floaters. Sometimes the gel shrinks enough to collapse away from the light sensitive lining at the back of your eye, which is called the retina. Once the gel has collapsed, some people see a large ring-shaped floater.

The collapse of vitreous gel can pull on your retina. If this happens you would see this as flashes of light – see ‘flashes’ below.

Floaters can also caused by some eye diseases that cause inflammation. This is not very common.

People at risk may include:

  • Short-sighted people
  • People that have had an eye operation such as cataract surgery
  • People that have had laser treatment after cataract surgery

 What should I do if I have floaters?

Most of the time floaters are harmless. Sometimes they may be annoying, but treatment is not advised.

Occasionally a sudden increase in floaters – either one or more large ones or a shower of tiny ones – may be a sign of a more serious eye disease such as retinal detachment – see ‘retinal detachment’ below. If that occurs you should consult your optometrist.


Some people may see flashes of light in front of one of their eyes, like small sparkles, lightening or fireworks. These tend to be in the extreme corners of your vision, come and go, and don’t obscure any part of your vision. The flashes don’t last for a defined length of time, and you may notice them more if you go from a light to a dark environment. They may continue for several months.

Flashes can occur when the gel in your eye becomes more liquid and “tugs” on the retina or may occur if you receive a hit in the eye. However, constant flashes may indicate a retinal tear or detachment and may be accompanied by a shadow at the edge of your vision. If this happens you should consult your optometrist straight away.

Flashes and migraines

Flashes are different to the shimmering or zig-zag lines that may be part of migraine. Migraine shimmers are a flickering of light, often only on one side of your vision with a sort of jagged pattern. This will often obscure a t least part of your vision (the left or right side). The shimmers usually go away after 10-20 minutes and may be followed by a headache, although some people may get migraine shimmers even if they do not have a headache afterwards.

Retinal detachment is when your retina pulls away from the back of your eye. A retinal tear or retinal detachment may lead to a sudden increase in floaters as well as flashes. You might notice a shadow at the edge of your vision too.

Who is at risk of retinal detachment?

Some people are more at risk of retinal detachment. These are people who:

  • Have had eye surgery, such as cataract operation or laser surgery after a cataract operation
  • Are moderately short sighted (over -3.00D)
  • Have had a previous eye injury
  • Have a family history of retinal detachment
  • Have had a previous retinal detachment in that eye or the other eye
  • Are over the age of 50
  • Have certain retinal diseases such as lattice or other retinal degeneration
  • Have certain systematic diseases such as Marfan syndrome.


Retinal detachment needs immediate attention. If you notice these symptoms you should contact your optometrist straight away. If you cannot do this you should seek urgent attention from an eye casualty department at the hospital. If there is not eye casualty department nearby you can go to your usual hospital casualty department, but it is best to go to an eye casualty department if you can. An ophthalmologist, a specialist eye doctor, will need to us eye drops and a special light to look inside your eyes to check if your retina is damaged.


This information is provided by the College of Optometrists. The College – a registered charity – is the professional body for optometry in the UK, working for the public benefit. It is a membership organisation and the most qualified practising optometrists in the UK are members. Membership of the College shows a commitment to the very highest clinical, ethical and professional standards.  Look for the letters MCOptom or FCOptom to see if your optometrist is a member.