Ask Dr. K: Most eye ‘floaters’ are a harmless nuisance

To understand floaters, here’s a quick refresher on how your eyes are built. The light that enters your eyes through the pupil passes through a crystalline lens inside the eye. The lens focuses the light on the back of your eye: the retina. It’s similar to the lens on a camera focusing light on the film (or, these days, on the digital sensor).

The retina is the light-sensitive area where the whole image is registered before it is sent to the brain. The brain then interprets the image. The retina registers the tennis ball coming toward you; the brain estimates where it will be within the next second so that you can move there to hit it.

Between the lens and the retina is a fluid called the vitreous. Floaters form in the vitreous. They are tiny clusters of cells or flecks of protein. When light coming into your eyes hits one of these little floaters, it casts a shadow on the retina. It’s that shadow that you see, and call a floater.

Most floaters are harmless. As you age, the vitreous fluid starts to get thicker and denser, leading to the clumps of cells and proteins. These changes in the vitreous also can cause suction that tugs on the retina. That can cause the retina to tear or to become detached. When that happens, a person suddenly sees new floaters and flashing lights. In addition, the person often has impaired vision out of the affected eye. That is not harmless: It’s a medical emergency. Prompt diagnosis and treatment can save a person’s vision.

So if you have a sudden change in the number of floaters or flashing lights, or sudden poor vision, get help immediately. If nothing has changed with your floaters, then the question is how much do they bother you. Floaters may break apart and dissolve naturally. On the other hand, new floaters can form.

Floaters can be removed with surgery. Eye surgery these days is much more effective and safe than it was decades ago, but there is always a risk with surgery. One of my patients had surgery and has been forever grateful.

Most of my patients just learn to live with floaters. If they become a nuisance, moving your eye up and down or left and right may shift the floaters and provide temporary relief.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.