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Patient Education: Flashes and Floaters


What are flashes?

Flashes are experienced as quick flashes of light which you see in your field of vision and may occur intermittently over days, weeks or months.

What causes flashes?

Filling the inside of your eye is a gel-like fluid called the vitreous.  The vitreous is attached to the nerve layer which lines the back of your eye, called the retina.

Flashes are a symptom of your retina being irritated or stimulated by something.

As we grow older the vitreous gel changes in consistency and may separate from the retina.  As the vitreous comes away from the retina it may pull at this delicate layer and cause flashes of light.  This process is normal and only causes a problem if the vitreous is so firmly attached that the pulling creates a tear in the retina.  The separation of the vitreous from the retina is called a posterior vitreous detachment.

As well as being part of the ageing process flashes may also occur in people who:

·        Have experienced trauma to the head/eye

·        Are near sighted (myopic)

·        Have undergone laser or surgical procedures on the eye

·        Have had inflammation inside the eye

Flashes may also be caused by migraine.  These flashes normally appear in both eyes, may last for up to 20 minutes at a time and often look like jagged lines or “heat waves”.  A migraine is caused by a spasm of blood vessels in the brain.  If a headache follows the flashes we call this a migraine headache.  If the flashes occur without the presence of a headache we call this ocular migraine.  These flashes are not caused by the vitreous pulling at the retina.

Are flashes ever serious?

Flashes themselves are not serious but may be a warning sign that something serious is occurring inside your eye.  If you notice a sudden onset of flashes you should see your ophthalmologist as soon as possible for an examination of the retina.

How are flashes treated?

Flashes themselves cannot be treated.  They are normally a symptom of detachment of the vitreous.  If the vitreous tears the retina while it is detaching this can cause serious problems such as bleeding and detachment of the retina itself.  These are serious complications and must be treated by an ophthalmologist as soon as possible.

What are floaters?

Floaters are tiny clumps of gel or cells inside the vitreous (the clear jelly-like fluid that fills the inside of your eye).  You may see these as small specks or clouds moving in your field of vision.  Often they are more obvious if you are looking at a plain background, like a blank wall or clear blue sky.

Even though the floaters look like they are in front of your eye, they are actually floating inside.  What you see are the shadows they cast on the retina.

Floaters can have different shapes such as little dots, circles, lines, clouds or cobwebs.

What causes floaters?

When people reach middle age the vitreous gel may start to thicken or shrink, forming clumps or strands inside the eye and may pull away from the retina (posterior vitreous detachment).  This is a common cause of floaters.

Are floaters ever serious?

Most people by the time they reach middle age will have floaters.  Floaters themselves are not a serious problem but may be a warning sign that there is a serious problem occurring inside the eye.  The detachment of the vitreous from the retina can cause tears and complications such as bleeding or retinal detachment.  Retinal tears, bleeding and retinal detachment are very serious problems and must be examined by an Ophthalmologist.  Urgent treatment such as laser or surgery may be required.

It is extremely important that if you notice sudden onset of floaters, an increase in existing floaters, or a shadow developing in your peripheral vision, you should contact your ophthalmologist right away.

How are floaters treated?

If the floaters are due to the changing consistency of the vitreous as part of the ageing process no treatment is required.  Sometimes the floaters may interfere with work or activities of daily living and may be surgically removed. 

If the floaters are a symptom of a more serious problem your ophthalmologist will discuss treatment options with you.