Web ExclusiveQ: Recently, I started to notice tiny threadlike shapes in my field of vision. My doctor says they are “floaters.” Should I be concerned?

A: “Floaters” is a catchall term for what look like dots, threads, or cobwebs drifting across your line of vision.

Floaters are tiny clusters of cells or flecks of protein that form in the vitreous, the fluid that fills the eyeball. What you’re actually seeing is the shadow these bits cast on the retina, the light-sensitive tissue at the back of the eye that allows us to see. Some people also see flashes of light. These occur when the vitreous bumps, rubs, or tugs against the retina. Most floaters and flashes are harmless and occur as a result of normal aging and shrinking of the vitreous.

Sometimes, though, the shrinking vitreous tugs on the retina and pulls away from it a little bit. This is called vitreous detachment. It triggers new floaters and flashes. Vitreous detachment usually doesn’t threaten vision. In about 15% of cases, vitreous detachment tears the retina. That tear can lead to a detached retina, a much more serious condition that can lead to vision loss. 

If you notice new floaters or flashes, call your doctor and arrange to see an eye specialist (ophthalmologist) as soon as possible. Prompt treatment can help prevent retinal detachment — and protect your sight.

For more information on common eye conditions in older adults, buy The Aging Eye, a Special Health Report from Harvard Medical School.