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HealthInfo Waitaha Canterbury

Floaters & flashes



See your optometrist, ophthalmologist or general practice team today if you have any of the four Fs.

You need to have these assessed urgently – on the same day. Over the weekend you can be assessed at an after-hours clinic, and they can refer you to an ophthalmologist urgently if necessary.

Dots and lines (floaters) or flashes of light in your vision are common, especially as you get older.

They aren't usually serious, particularly:

The commonest cause is posterior vitreous detachment, which is when the gel-like fluid in the back of your eye shrinks in size and pulls on the inner lining of your eye (retina).


Visual floaters are blobs, thread-like strands, fine cobwebs or just dull shadows and spots in your vision. They're more noticeable when you look at a white wall or plain, light-coloured surface such as the sky.

Floaters are actually particles within the clear gel-like substance that fills the inside of your eyeball (vitreous fluid). These particles cast shadows on your retina, the light-sensitive layer at the back of your eye. As you get older, floaters become more common.

The floaters move as your eye moves but tend to drift away when the movement stops.

Floaters are usually harmless and although annoying, tend to become less noticeable with time.

If you suddenly get new floaters or a big increase in the number of floaters, you should get your eyes checked in case you have a retinal detachment.


Flashes are sparks or strands of light that flicker across your vision.

If you see light flashes in dim light or at night, you do not usually need to worry. But if you see flashes of light during the daytime, you need to have your eyes checked urgently (on the same day) as this can be a sign of an early retinal detachment.

Migraine sufferers can experience a different type of light flash called an aura. An aura is shimmery lights and zigzag patterns in your vision, sometimes followed by blind areas. You may or may not get a headache and nausea after this. If this is new for you, see your general practice team.

On the next page: Retinal detachment

Adapted by HealthInfo clinical advisers. Last reviewed March 2023.


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Review key: HIFRT-139694