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Floaters and Flashes: Cause for Concern?

Have you ever looked up at the bright blue sky, or stared at a plain background and noticed little "floaters" dancing around your field of vision? They may look like tiny cobwebs, wiggly floating strands, or tiny dots—and they come and go. Whatever shape they take, these floaters are usually harmless. And though they may look like they're in front of your eye, they're actually inside it.

The Cause

As our eyes age, the vitreous gel inside them may start to thicken or shrink. They pull slightly away from the back wall of the eye, causing clumps or strands inside the vitreous, the clear, gel-like fluid that fills the inside of your eye. These vitreous clumps cast shadows on the retina—the layer of cells lining the back of the eye that senses light and allows you to see. This common cause of floaters is technically called a "posterior vitreous detachment," and is more common in people who:

  • Are middle-age
  • Are nearsighted
  • Have had cataract operations
  • Have had YAG laser surgery
  • Have had inflammation inside the eye

There may be cause for concern if new floaters appear all at once, out of nowhere—especially if you are over 45 years of age. The retina can tear if the shrinking vitreous gel pulls away from the wall of the eye suddenly, and more forcefully than is common. This sometimes causes a small amount of bleeding in the eye that may appear as new floaters. A torn retina is always a serious problem, since it can lead to a retinal detachment. You should see your ophthalmologist as soon as possible if even one new floater or sudden flashes of light appear suddenly.

Flashing Lights

If you've ever been hit in the eye or head and seen "stars," they may have looked like flashing lights or lightning streaks. As we age, this may be another common sensation, also caused when the vitreous gel rubs or pulls on the eye. It can come and go for several weeks or months. But, as is the case with floaters, if you notice a sudden onset of light flashes, contact your ophthalmologist immediately in case the retina has been torn.


Some people experience flashes of light that appear as jagged lines or "heat waves" in both eyes, and they can last for up to 20 minutes. These types of flashes are usually caused by a spasm of blood vessels in the brain, which is called a migraine. If a headache follows the flashes, it's called a migraine headache. If these kinds of flashes occur without a headache, it's called an ophthalmic (or ocular) migraine and you should contact your ophthalmologist. If light is a trigger for your migraines, special filtered lenses may help.