Black floaters in your eyes are almost always caused by tiny clumps of collagen fiber inside the gel that fills your eyeball. As this gel ages and breaks down, those clumps cast shadows on the light-sensitive tissue at the back of your eye, and your brain registers them as dark spots, strings, or cobweb-like shapes drifting across your vision. Most floaters are harmless, but in some cases they signal something more serious happening inside the eye.
How Floaters Form Inside the Eye
Your eye is filled with a clear, jelly-like substance called the vitreous. It’s 99% water, held together by a sparse scaffolding of collagen fibers and a molecule called hyaluronic acid. When you’re young, this gel is stable and transparent. Over time, however, the gel begins to liquefy and shrink, a process called vitreous syneresis. As it breaks down, collagen fibers that were once evenly distributed start clumping together into tiny aggregates.
These clumps float freely inside the vitreous cavity. When light enters your eye, the clumps scatter it and cast shadows onto the retina. That’s what you perceive as a floater: not an object in front of your eye, but a shadow inside it. The shapes can look like specks, threads, worm-like squiggles, or cobwebs, and they drift when you move your eyes. If you try to look directly at one, it appears to dart away because the clump moves with the fluid inside your eye.
Age-Related Vitreous Detachment
The most common trigger for a noticeable increase in floaters is posterior vitreous detachment (PVD). As the vitreous gel continues to shrink, it eventually can no longer fill the entire cavity of the eye. The gel pulls away from the retina, sometimes all at once, sometimes gradually. When it separates, the detached vitreous itself becomes a large, irregular floater that can cast a prominent shadow.
PVD is extremely common in older adults. After age 50, roughly 53% of people have some degree of vitreous detachment. Between ages 66 and 86, that figure rises to about 66%. Postmortem studies found PVD in 27% of eyes by the seventh decade of life and 63% by the eighth. In most cases, PVD completes without complications and the floaters become less noticeable over weeks to months as the brain adapts.
Nearsightedness and Younger Eyes
Floaters aren’t exclusive to older adults. People who are nearsighted (myopic) tend to develop them earlier because their eyes are longer than average, which puts extra mechanical stress on the vitreous gel. That stress accelerates collagen fiber aggregation, producing the same clumping and shadow-casting process that normally takes decades. If you’re significantly nearsighted and noticing floaters in your 20s or 30s, the underlying mechanism is the same, just happening on a faster timeline.
Bleeding Inside the Eye
Not all floaters come from collagen clumps. Blood that leaks into the vitreous cavity can also appear as dark floaters, cobwebs, or a red-tinted haze across your vision. This is called a vitreous hemorrhage, and it typically causes a sudden, painless drop in visual clarity along with new floating shapes.
The most frequent cause in people over 40 is proliferative diabetic retinopathy. Diabetes damages the small blood vessels of the retina, and the eye responds by growing new, fragile replacement vessels. These new vessels lack the structural integrity of normal ones and bleed easily, releasing blood into the vitreous. Retinal vein blockages and sickle cell disease can trigger the same process.
In people under 40, the leading cause of vitreous hemorrhage is eye trauma. A blunt hit or penetrating injury can rupture normal retinal blood vessels directly, flooding the vitreous with blood. The onset is immediate and obvious.
Eye Inflammation (Uveitis)
Inflammation inside the eye can produce floaters that aren’t collagen or blood at all, but white blood cells and inflammatory debris. A condition called intermediate uveitis causes immune cells to accumulate in the vitreous, where they float freely and scatter light much like collagen clumps do. Larger collections of these cells, sometimes called “snowballs,” can also form.
Uveitis-related floaters are usually accompanied by blurred vision and sometimes eye redness or pain, depending on which part of the eye is inflamed. The condition can be linked to autoimmune diseases, infections, or sometimes no identifiable cause. Unlike age-related floaters, these require treatment to control the underlying inflammation.
When Floaters Signal a Retinal Tear
The reason eye specialists take sudden floaters seriously is the risk of a retinal tear. During posterior vitreous detachment, the shrinking gel tugs on the retina as it separates. If the retina is thin or the adhesion is strong, the pulling can rip a small hole in the tissue. Fluid from the liquefied vitreous can then seep through the tear and peel the retina away from its supporting layer, like wallpaper lifting off a wall. That progression from tear to retinal detachment can cause permanent vision loss if not treated quickly.
A retinal tear sometimes produces no symptoms at all. When it does, the warning signs are distinct: a sudden shower of many new floaters, flashes of light in the same eye, a gray curtain or blurry area creeping across part of your vision, or darkness closing in from the sides. These symptoms are painless, which can make them easy to dismiss. They shouldn’t be. Any combination of a sudden increase in floaters with light flashes or vision changes warrants immediate evaluation by an eye specialist.
How Floaters Are Diagnosed
A dilated eye exam is the standard way to investigate floaters. Your eye specialist places drops in your eyes to widen your pupils, which allows them to see through to the back of the eye and examine the vitreous, retina, and optic nerve directly. This exam can distinguish harmless collagen floaters from a retinal tear, vitreous hemorrhage, or inflammatory cells. If the vitreous is too cloudy for a clear view (from heavy bleeding, for example), an ultrasound of the eye can image the structures behind the obstruction.
Treatment Options
Most floaters don’t require treatment. The brain gradually learns to ignore them, and many people find that within a few months the floaters become far less noticeable even though they haven’t physically disappeared. They tend to be most visible against bright, uniform backgrounds like a white wall or blue sky, and less apparent in everyday visual environments.
For floaters that remain severely disruptive to daily life, two interventions exist. Laser vitreolysis uses a focused laser beam to break up or vaporize the collagen clumps inside the eye. It tends to work best when the floater is a single, well-defined opacity suspended centrally in the vitreous rather than a diffuse cloud of small particles. The second option, vitrectomy, is a surgical procedure that removes the vitreous gel entirely and replaces it with a clear fluid. It’s effective but carries risks including cataract formation, retinal tears, retinal detachment, and infection.
No randomized controlled trials have directly compared laser vitreolysis to vitrectomy, so there isn’t strong evidence favoring one over the other. In practice, most specialists reserve vitrectomy for cases where floaters significantly impair vision and quality of life, and recommend laser treatment as a less invasive first step when the floater’s location and shape make it a good candidate.
When floaters result from an underlying condition like diabetic retinopathy, uveitis, or a retinal tear, treatment targets the cause rather than the floaters themselves. Treating the bleeding, inflammation, or tear typically resolves or reduces the associated floaters over time.