Flashes and floaters

Flashes of light or black floaters that look like spiders or tadpoles and move around as you move your eye are quite commonly seen by people with normal eyes.

What are flashes and floaters?

Floaters are shapes or shadows that people can see drifting across their vision. The exact form and source of these floaters vary – they may appear as small dots or irregularly shaped strands. Floaters are generally harmless and can become less noticeable over time, however in some cases they can be an indication of serious eye conditions especially when they are associated with flashes of light.

What are the causes of flashes and floaters?

The hollow space in the middle of your eyeball is filled by a clear, jelly-like substance called the vitreous humor. As the vitreous ages, it liquifies and becomes less firm, and strands of a protein called collagen become visible within it. These strands swirl gently when the eye moves.

Normally, light travels through the clear gel of vitreous humor in order to reach the retina, 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 onto the retina, giving rise to the perception of floaters.

If you have had an eye operation, such as cataract surgery, you are more likely to experience floater symptoms and related conditions. In some cases, floaters may also be the result of a number of other processes including:

  • Infection
  • Inflammation (uveitis)
  • Eye disease, or
  • Eye injury

In nearly all people, usually over the age of 40, the vitreous humor separates from the retina. When this happens, it can tug on the retina, causing the eye to see flashes of bright white light. A sudden increase (shower) of floaters in the eye can sometimes be seen at the same time. This is process of the vitreous humor separating from the retina is called a posterior vitreous detachment or PVD, and may lead to retinal tears and retinal detachment.

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