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What's the difference between eye floaters and flashes?

view of a little girl from a person experiencing eye floaters and eye flashes

Eye floaters and eye flashes are examples of entoptic phenomena — which means they are visual effects whose source is within the eye itself.

The key differences between eye floaters and flashes are their appearance and causes:

Appearance 

Eye floaters are shadowy spots, clumps, and irregular linear and fuzzball-like shapes (like the “pilling” of the fibers of a sweater) that drift slowly across your field of view — which makes them appear as though they are floating in front of your eyes.

Eye flashes appear just as their name suggests — they are bright (often arc-shaped or jagged) flashes of light, which tend to appear more frequently in your peripheral vision.

Causes

Eye floaters are caused by discrete clusters of a protein called collagen within the vitreous of the eye. The vitreous is a gel-like fluid that fills the large cavity inside the back of the eye (the space between the lens and the retina). 

These clusters of collagen are opaque and cast shadows on the retina when light enters the eye. It is these shadows that we perceive as floaters in our vision.

Eye flashes are caused by the traction (pulling) on the surface of the retina that occurs when the back portion of the vitreous begins to separate from the retina. This is a normal aging change that coincides with the vitreous becoming more liquid and less gel-like in nature. 

This liquefaction of the vitreous is also what causes normally clear and transparent collagen fibers to clump together and form opaque clusters that lead to floaters. 

Eye floaters and eye flashes can appear suddenly and may occur separately or together. 

Floaters are very common and usually are not a symptom that anything is seriously wrong with your eyes (especially if you notice only a few floaters and they aren’t accompanied by flashes of light). 

Eye flashes, on the other hand, could signal you are at risk of a retinal detachment, which is a medical emergency. If you suddenly see flashes of light and a large number of floaters, see an eye doctor immediately to rule out the beginning of a detached retina.   

SEE RELATED: What causes floaters?

Eye floaters are almost always permanent, but they usually fade or become less noticeable over time. Frequently, they may eventually move out of your field of view, appearing to go away on their own.

Eye flashes, on the other hand, occur erratically and tend to be temporary. If the vitreous pulls away from the retina (a condition called posterior vitreous detachment) without causing a retinal tear or detachment, the flashes usually stop. This can occur within hours, days or weeks. 

Ocular migraines or migraines with aura can also cause the appearance of flashing lights. If light flashes go on for longer than 30 minutes and aren’t accompanied by other migraine symptoms, it’s unlikely that one of these migraines is causing your flashes.

Migraines can cause other visual sensations as well, but eye floaters aren’t one of them.

Though there are differences between flashes and floaters, they both tend to occur more frequently as people age, but they can also show up in younger people. People who are nearsighted or have had cataract surgery are more at risk to develop eye floaters or periodic eye flashes in their lifetimes.

Flashes and floaters are usually harmless, but they can also be symptoms of a retinal tear or detachment (or that you are at elevated risk of these serious conditions).

If you suddenly experience flashes of light or a sudden and significant increase in floaters — particularly if you also notice a darkening of part of your visual field — see an eye doctor immediately. 

READ MORE: Eye floaters treatment

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Gary Heiting, OD

Gary Heiting, OD, is a former senior editor of AllAboutVision.com. Dr. Heiting has more than 30 years of experience as an eye care provider, health educator and consultant to the eyewear ... Read more