Eye Floaters and Flashes of Light: When Are They an Emergency?

Nearly everyone has experienced floaters — those translucent specks, threads, or cobweb-like shapes that drift slowly across your visual field when you look at a bright surface. For most people, most of the time, floaters are a benign and normal part of how the eye ages. But there are specific circumstances in which new or changing floaters represent a serious warning sign that requires immediate evaluation.

What Causes Floaters?

Floaters are shadows cast on the retina by debris within the vitreous — the gel-like substance that fills the interior of the eye. As the vitreous ages, it gradually liquefies and the collagen fibers within it begin to clump. This process, called posterior vitreous detachment (PVD), is a normal part of aging that happens to virtually everyone — typically beginning in the fifties and sixties, but earlier in people with high myopia.

When Floaters Are Normal and Benign

Floaters you have had for months or years, that are stable in number and character, and that do not interfere meaningfully with your daily vision are almost certainly harmless vitreous floaters. Your brain tends to adapt to them over time.

When Floaters Are a Medical Emergency

• A sudden shower of new floaters you have never had before, or a dramatic increase in existing floaters in a short period of time
• Floaters accompanied by flashes of light in your peripheral vision — flashes indicate the vitreous is pulling on the retina, which can cause a tear
• A dark shadow or curtain appearing at the edge of your vision and expanding — this is a sign of retinal detachment
• Any floaters following eye trauma, even if it seemed minor

Understanding Retinal Tears and Detachment

During posterior vitreous detachment, the vitreous usually separates from the retina cleanly. But in some cases — particularly in people with high myopia — the vitreous pulls hard enough to tear the retinal tissue. A retinal tear, if caught early, can typically be sealed using in-office laser photocoagulation. Left untreated, fluid can pass through the tear and lift the retina off the inner wall of the eye, causing retinal detachment that requires surgical repair.