Almost everyone has them. Those little fuzzy, translucent bits which float around happily in your eye. Usually when you try to look or focus directly on one, they float away just as quickly as your eye can move. What are they, and are they harmful?

What Are Eye Floaters?

Those little floating blurry particles that appear as bits of fuzzy dust and float around in your eye are usually referred to as ‘floaters’ by doctors but the actual medical term is “muscae volitantes” (fluttering flies in Latin). Muscae volitantes are described or defined as particles, soot, spiders, cobwebs, worms, dark streaks, or rings which float in your field of vision. Nearly everybody experiences them, though in individuals who are nearsighted, they’re much more common. Generally – not always – they’re fairly harmless.

Floaters are believed to be the remnants of the hyaloid artery. It’s an artery which nourished parts of your eye during fetal development. As you matured in the womb, the artery eventually withered away. While it was active and doing its job, the artery floated around in your vitreous humor, which is the fluid that fills your eyeball behind the lens. It ran from the lens in your eye to the other end where the optic nerve comes in. After the third month of fetal development, it began to atrophy. Around the 7th month, the blood stopped flowing through the artery and it slowly disintegrated. Most of the little bits of debris were evacuated by the time you were born, but tiny amounts of it still remain in your vitreous humor and will stay with you for the rest of your life.

Other Causes

Retinal tears in the eye may also cause floaters if red blood cells are released into the eye from leaky blood vessels. Other (more rare) causes for floaters include cystoid macular edema and asteroid hyalosis. Asteroid hyalosis is an anomaly of the vitreous humour, and is caused by calcium clumps attaching themselves to the collagen network. These clumps are different in that they only move slightly with eye movement then return to their fixed position.

Do They Increase With Age?

The number of floaters in your eyes tends to increase with age due to the fibrous clumps and membranes which can form in your vitreous fluid. In some extreme cases, the vitreous material itself may pull away from the inside of your eyeball, which means what you’re seeing may actually be crudniks stuck inside the back of your eyeball. It does sound like cause for concern but is in fact totally benign, and will not impair vision.

Are Eye Floaters Always Benign?

Not always. In some cases, floaters can be stray blood cells which are caused by a hemorrhage of the tiny vessels inside your eye. This can be caused by a simple blow to the head or a multitude of related trauma. Suddenly seeing a shower of spots accompanied by bright flashes of light can also be a sign that you are about to suffer a detached retina. Eye floaters can also be the result of an eye infection.

Do Eye Parasites Exist?

Another non-benign reason for floaters is something that may give you the creeps – intraocular parasites. While extremely rare, and generally not found in first world countries, some parasites do have the capability to live and reside inside your eye. One such parasite is mansonella perstans. Mansonella perstans (also known as Bung eye disease) are little filarial nematodes transmitted by bloodsucking flies in sub-saharan Africa, South America and the Caribbean.

While a parasite living inside your eyeball sounds extremely gross, it doesn’t pose much risk to overall health and is considered one of the more ‘mild’ parasites that a human could acquire. It is also quite easy to treat.

Can Eye Floaters Be Removed?

When a person experiences an extremely large number of eye floaters and vision is being seriously impaired, doctors can perform what is known as a ‘vitrectomy’. This is when the fluid is completely drained out of your eye (and along with it, the floaters) and replaced with a similar but inert substance. Due to it being an extremely delicate process, it is a rare procedure and is only performed in only the most extreme cases.

Photos are available under a Creative Commons Attribution license by Wikicommons.

References:

American Academy of Ophthalmology. “Floaters and Flashes: A Closer Look” San Francisco: AAO, 2006. ISBN 1-56055-371-5

Dictionary of Visual Science – Cline D; Hofstetter HW; Griffin JR. Boston 1997 ISBN 0-7506-9895-0

Wikipedia