Floaters

Floaters often occur as part of the natural ageing process. As you get older, your risk of developing floaters increases. Floaters tend to occur in people who are over 40 years of age. They are most common in people in their 60s and 70s.

Natural debris

The large area in the middle of your eyeball is filled with a clear, jelly-like substance called vitreous humour. As you get older, the vitreous humour can become less firm and strands of a protein called collagen may become visible within it. The collagen strands may appear to swirl as your eye moves.

Normally, light travels through the clear layer of vitreous humour in order to reach the retina. The retina is the light sensitive layer of cells and tissue at the back of your eye which transmits images to your brain via the optic nerve. Any objects, such as floaters, that are in the vitreous humour will cast shadows on to the retina.

Posterior vitreous detachment (PVD)

Posterior vitreous detachment (PVD) can be the result of changes that occur to the vitreous humour of the eye, as the eye gets older. PVD is a common condition that occurs in about 75% of people over 65.

With age, 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 can be another symptom of PVD. Flashing may occur when the outer part of the vitreous humour pulls on the light sensitive tissue of the retina. The pulling stimulates the retina, causing your brain to interpret it as a light signal. This creates the sensation of flashing lights.

Retinal tears

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. The red blood cells may appear as tiny black dots, or they may look like smoke. However, as the blood is re-absorbed back into the retina, floaters that are caused by tears tend to disappear over the course of a few months.

In approximately half of all people, the vitreous humour has separated from the retina by the time they are 50. This doesn't usually cause any problems, and most people aren't even aware that it has happened.

In some cases, the vitreous humour remains attached to parts of the retina and it tears the retina as it pulls away. If the retina tears, blood that escapes into the vitreous humour can cause a ‘shower’ of lots of floaters at once. You may also see flashes of bright, white light in your vision that look a little like lightening 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 ‘zig-zag’ pattern across your field of vision).

Floaters and flashes do not usually cause long-term visual impairment, but if you experience them it is important that you visit an eye care specialist, such as an optometrist, in order to have an eye examination.

Retinal detachment

If you have retinal tears, you will need to be treated as soon as possible because tears can lead to retinal detachment. Retinal detachment occurs when the retina separates from the wall at the back of the eye. If this happens, it can damage your sight.

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

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

Other causes

If you have had eye surgery, such as a cataract operation, you are more likely to experience floaters, PVD, retinal tears, and retinal detachment. In some cases, floaters may also be the result of a number of other causes including:

• infection,
• inflammation (uveitis),
• eye disease, or
• eye injury.

Visiting your optometrist

Even though floaters are usually harmless and do not affect your vision, it is important that you visit an optometrist (optician) on a regular basis (at least once every two years). You should tell your GP, or your optometrist, if you have the symptoms of floaters.

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

Although rare, floaters may be a sign of retinal tears or retinal detachment. The ophthalmologist will be able to check for this by examining your retina.

Eye examination

By looking through your pupil, the ophthalmologist will be able 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 current light conditions.

If your ophthalmologist needs to get a clearer view of your retina, you may have a procedure known as dilation. This is where eye drops are used to make your pupil wider, allowing the whole of your retina to be examined.

The ophthalmologist may use an instrument, called an ophthalmoscope, to examine your eye. An ophthalmoscope has a light on the end and produces a magnified image of your eye. After the examination, your vision may be a little blurry, and you may be sensitive to light for a few hours.

Other tests

In order to get a better understanding of your eye symptoms, the ophthalmologist may also carry out a number of other tests, such as asking you to look in different directions, pushing on your eye using a special instrument, and using a very bright light to examine your retina more closely.

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

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

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

Floaters occur in a variety of forms

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

• dots,
• circles,
• lines,
• cobwebs, or
• other shapes.

You may notice lots of 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 make activities that involve high levels of concentration, such as reading or driving, difficult.

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

In the majority of cases, floaters do not cause any significant problems and do not require treatment. Eye drops, or other similar forms 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. It will cause the vitreous humour in your eye to move around, which may help by shifting the floater elsewhere.

Vitrectomy

If you have floaters which do not improve over time, or if they significantly affect your vision, a surgical procedure, known as a vitrectomy, may be considered.

The aim of a vitrectomy is to remove the vitreous humour in your eye along with any floating debris and replace it with a saline solution. However, vitrectomies are rarely carried out due to the associated risks of eye surgery.

 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 of water, you will not notice any difference after having a vitrectomy.

 Possible complications of a vitrectomy include:

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