Floaters are caused by small pieces of debris that float in the vitreous humour of the eye.

They occur behind the lens and in front of the retina. The lens is a small clear structure that focuses light as it enters the eye. The retina is the light-sensitive tissue that lines the inside surface of the back of the eye.

Vitreous humour is a clear, jelly-like substance that fills the space in the middle of the eyeball. It is mostly (99%) made up of water. The other 1% is made up of substances that help maintain the shape of the vitreous.

Floaters occur as part of the natural ageing process. Some people may have posterior vitreous detachment (PVD), which is where the vitreous jelly comes away from the retina (see below). This may cause a sudden increase in the number of floaters.

Ageing process

As you get older, your risk of developing floaters increases. They tend to occur in people over 40 years of age, and are most common in those in their 60s and 70s. However, some younger people may also develop floaters.

As you get older, the vitreous humour in the middle of your eyeball can become softer, and strands of a protein called collagen may become visible within it. The collagen strands may appear to swirl as your eyes move.

Normally, light travels through the clear layer of vitreous humour to reach the retina. The light-sensitive layer of cells at the back of your eye that form the retina transmit images to your brain via the optic nerve. Any objects that are in the vitreous humour, such as floaters, will cast shadows onto the retina.

Posterior vitreous detachment (PVD)

Floaters can be a symptom of posterior vitreous detachment (PVD). This is a common condition that occurs in around three-quarters of people over 65 years of age. PVD can occur as the result of changes to the vitreous humour as the eye gets older.

As your eye ages, the central part of the vitreous humour becomes more liquid and the outer part, known as the cortex (which contains more collagen), starts to shrink away from the retina. Floaters develop as a result of the collagen thickening and clumping together.

As well as floaters, flashing lights can be another symptom of PVD. This can occur if the outer part of the vitreous humour pulls on the light-sensitive tissue of the retina. The pulling stimulates the retina, which causes your brain to interpret it as a light signal and creates the sensation of flashing lights.

You can read more about PVD on the RNIB website.

Retinal tears

In about half of all people, the vitreous humour has separated from the retina by the time they are 50 years of age. This does not usually cause any problems and most people are not even aware it has happened.

In a few cases of PVD, when the vitreous humour pulls on the retina, it can cause the tiny blood vessels in the retina to burst and bleed into the vitreous humour. The red blood cells may appear as tiny black dots or they may look like smoke. However, as the blood is absorbed back into the retina, these floaters tend to disappear over the course of a few months.

In some cases, the vitreous humour remains attached to parts of the retina and tears the retina as it pulls away. If the retina tears, blood that escapes into the vitreous humour can cause a shower of floaters all at once. You may also see flashes of bright, white light in your field of vision that look similar to lightning streaks.

It is important to be aware that flashes in your vision are not necessarily a sign of retinal tears or retinal detachment (see below). They may have another cause, such as a migraine with aura (a headache with a zigzag pattern across your field of vision).

Floaters and flashes do not usually cause long-term visual impairment. However, if you experience them, you should visit an optician to have your eyes examined.

Find an optician near you.

Retinal detachment

If you have a retinal tear, you will need to be treated as soon as possible because tears can lead to retinal detachment. This is where the retina separates from the wall at the back of the eye which can damage your sight.

Retinal detachment is rare, affecting about 1 in every 10,000 people each year.

After the light has passed through the eye and reaches the retina, the retina changes the light into meaningful electrical signals. The signals are sent through the optic nerve to the brain, where they are translated into the images you see.

If the retina is damaged, the images received by your brain will become patchy or may be lost completely.

In rare cases, floaters may be a sign of retinal detachment. If your retina is detached, you will usually experience:

• a large number of floaters
• bright, flashing lights
• some loss of vision

If you think you may have retinal detachment, seek immediate medical attention from either your GP or optician.

Read more about retinal detachment.

Other causes

If you have had eye surgery, such as cataract surgery, you are more likely to experience floaters, PVD and, more rarely, retinal tears and retinal detachment. In some cases, floaters may also be caused by: 

• infection 
• uveitis
• eye disease 
• eye injury 

Floaters are also more common in people who have:

• short-sightedness (myopia) – where distant objects appear blurred, while close objects can still be seen clearly
• diabetes – a lifelong condition that causes a person’s blood sugar level to become too high

As floaters and flashes can be caused by a number of eye conditions, some of which can affect your vision, it is always best to have your eyes checked by an eye care specialist. You should also visit a specialist if you have floaters or flashes that get worse.

Read more about how floaters are diagnosed.

Although floaters are usually harmless and do not significantly affect your vision, you should have your eyes checked by an optician on a regular basis (at least once every two years).

You can use the post code search facility to find opticians in your local area.

Tell your optician if you have symptoms of floaters. They may ask about your:

• symptoms – including how long you have had floaters
• medical history – for example, whether you have previously injured your eye or had eye surgery

Visit your optician immediately if a new floater suddenly appears or if there is a rapid increase in the number of floaters you can see. They may refer you to an ophthalmologist (a specialist in diagnosing and treating eye conditions).

In rare cases, floaters may be a sign of retinal tears or retinal detachment. The ophthalmologist will check for this by examining your retina (the light-sensitive layer of cells that line the back of the eye).

Examining the retina

By looking through your pupil, the ophthalmologist will be able to see a small part of your retina. The pupil is the hole at the front of your eye that increases and decreases in size depending on the light conditions.

If the ophthalmologist needs a clearer view of your retina, a procedure known as dilation may be used. This is where eye drops are used to widen your pupil so the whole of your retina can be examined.

The ophthalmologist may use an instrument called a slit lamp to examine your eyes. A slit lamp has a lens and a bright light to enable the inside of your eye to be examined. After the examination, your vision may be a little blurry and your eyes will be sensitive to light for a few hours. 

Other tests

To get a better understanding of your eye symptoms, the ophthalmologist may also carry out other tests. For example, they may:

• ask you to look in different directions
• push on your eye using a special instrument
• examine your retina more closely using a very bright light

Eye pressure test (tonometry)

An eye pressure test (tonometry) uses an instrument called a tonometer to measure the pressure inside your eye (intraocular pressure).

During the test, a small amount of anaesthetic and dye will be placed onto your cornea (the transparent layer of tissue that covers the front of the eye).

A blue light from the head of the tonometer will be held against your eye to measure the intraocular pressure. A reduction in intraocular pressure may be a sign of retinal detachment.

Floaters are small shapes that some people see floating in their field of vision.

They can be different shapes and sizes and may look like:

• tiny black dots  
• small, shadowy dots  
• larger cloud-like spots 
• long, narrow strands

The shapes appear to float in front of everything that a person looks at.

Read more about the symptoms of floaters. 

What causes floaters?

Floaters are small pieces of debris that float in the eye’s vitreous humour. Vitreous humour is a clear, jelly-like substance that fills the space in the middle of the eyeball.

The debris casts shadows on to the retina (the light-sensitive tissue lining the back of the eye). If you have floaters, it is these shadows you will see.

Floaters can occur as your eyes change with age. In most cases, they do not cause significant problems and do not require treatment.

In rare cases, floaters may be a sign of a retinal tear or retinal detachment (where the retina starts to pull away from the blood vessels that supply it with oxygen and nutrients).

Read more about the causes of floaters.

Floaters cannot be prevented because they are part of the natural ageing process.

When to seek medical help

Visit your optician immediately if you notice an increase or sudden change in your floaters, particularly if you notice white flashes.

Your optician may refer you to an ophthalmologist (a specialist in diagnosing and treating eye conditions) who can check your retina for tears.

Even though floaters are usually harmless and do not significantly affect your vision, it’s important you have your eyes checked regularly by an optician (at least once every two years).

Read more about diagnosing floaters.

Treating floaters

In most cases, floaters do not cause major problems and do not require treatment. Eye drops or similar types of medication will not make floaters disappear.

After a while, your brain learns to ignore floaters and you may not notice them. If a floater appears in your direct line of vision, moving your eye up and down may help. This causes the vitreous humour in your eye to move around, which can shift the floater elsewhere.

If your floaters do not improve over time, or if they significantly affect your vision, a vitrectomy may be recommended. This is a surgical operation to remove the vitreous humour in your eye along with any floating debris and replace it with a saline (salty) solution.

If your retina has become detached, surgery is the only way to re-attach it. Without surgery, a total loss of vision is almost certain. In 90% of cases, only one operation is needed to re-attach the retina.

Read more about treating floaters.

If you have floaters, you may not notice them all of the time. When your eyes are still or you are gazing into space, you may see them drift slowly across your field of vision.

Floaters are usually grey and semi-transparent. They may appear to move quickly when you move your eyes to look in different directions.

However, floaters do not tend to follow eye movement precisely, and will often seem to dart away as you try to look directly at them.

Floaters are often most noticeable when you are looking at a light-coloured background, such as a white wall or clear sky.

Different forms of floaters

Floaters can occur in a variety of different forms. They may appear as:

• dots 
• circles 
• lines 
• cobwebs 
• other shapes

You may have many small floaters in your field of vision or just one or two larger ones. Most floaters are small and quickly move out of your field of vision.

Larger floaters can be distracting and may make activities involving high levels of concentration, such as reading or driving, difficult.

When to visit your optician

Floaters are usually harmless and do not significantly affect your vision. However, it’s important you have your eyes checked by an optician regularly (at least once every two years).

Find an optician near you.

You should visit your optician immediately if a new floater suddenly appears, or if there is a rapid increase in the number of floaters you can see. They may refer you to an ophthalmologist (a specialist in diagnosing and treating eye conditions).

Occasionally, floaters can be a symptom of retinal tears or retinal detachment. The ophthalmologist will check for this by examining your retina (the light-sensitive cells at the back of the eye).

If your retina is detached, you will usually experience:

• a large number of floaters
• bright, flashing lights
• some loss of vision

If you think you may have retinal detachment, seek immediate medical attention from either your GP or optician.

Read more about diagnosing floaters.

In most cases, floaters do not cause significant problems and do not require treatment.

Eye drops or similar types of medication are ineffective and will not make floaters disappear.

After a while, your brain may learn to ignore floaters and you may not notice them. If a floater appears directly in your line of vision, moving your eye up and down may help. This causes the jelly-like substance inside your eye (the vitreous humour) to move around, which may help shift the floater elsewhere.

Monitoring your condition

If you have floaters, your optician may ask you to return for a follow-up appointment two to six months after your symptoms begin to check that your retina is stable. The retina is the light-sensitive layer of cells that line the inside of the back of your eye.

If your vision is unaffected and your floaters are not getting any worse, you may be advised to have an eye appointment every one to two years. However, if your symptoms worsen at any time, you should seek immediate advice from either your GP or optician.

Vitrectomy

A vitrectomy is a surgical procedure to remove the vitreous humour in your eye along with any floating debris, and replace it with a saline (salty) solution.

A vitrectomy may be recommended as a possible treatment option if you have floaters that do not improve over time, or if they significantly affect your vision. However, vitrectomies are rarely carried out due to risks associated with eye surgery, and the procedure may not be available on the NHS.

Before having a vitrectomy your eye will be numbed with a local anaesthetic. During the procedure, the vitreous humour will be removed from the vitreous body of your eye and replaced with saline solution.

As the vitreous humour is mostly made up of water, you will not notice any difference to your vision after having a vitrectomy. However, possible complications may include:

• retinal tears 
• retinal detachment 
• cataracts (cloudy patches in the lens of the eye)