Most spots in your vision are caused by tiny clumps of collagen floating inside the gel-like fluid that fills your eye. These clumps cast shadows on your retina, and your brain registers them as dark specks, cobwebs, or squiggly lines drifting across your field of view. They’re extremely common and usually harmless. In some cases, though, spots signal something more urgent, like a tear in the retina or bleeding inside the eye.
How Floaters Form Inside Your Eye
Your eye is filled with a clear, jelly-like substance called the vitreous. It’s about 99% water, held together by a sparse scaffold of collagen fibers and a sugar-based molecule called hyaluronic acid. As you age, this gel gradually breaks down and liquefies, a process called vitreous syneresis. When that happens, the collagen fibers lose their even spacing, tangle together, and form small clumps. Those clumps drift through your field of vision and are most noticeable against bright backgrounds like a white wall or blue sky.
Floaters are so common that studies of smartphone users found roughly 76% of respondents reported experiencing them, with no significant difference across age, gender, race, or eye color in younger populations. While the breakdown of the vitreous accelerates after age 50, plenty of people in their twenties and thirties notice floaters too.
Posterior Vitreous Detachment
The most common cause of a sudden, noticeable increase in floaters is posterior vitreous detachment, or PVD. As the vitreous shrinks over time, it eventually pulls away from the retina at the back of the eye. This separation often releases a burst of new floaters, described as cobweb-shaped particles from the dense collagen at the back of the vitreous. About 67% of people with a PVD also experience blurred vision.
PVD typically comes with flashes of light, especially in your peripheral vision. These flashes are quick, more obvious in dim environments, and triggered by head or eye movement. The early stages of PVD are often completely silent, only becoming noticeable once the vitreous separates from the optic disc. For most people, PVD is a normal part of aging and resolves on its own, though floaters can persist for six months to a year or longer.
Migraine Aura
Not all spots in your vision come from something physically floating in your eye. Migraine aura produces visual disturbances that originate in the brain, caused by a wave of electrical activity spreading across the visual cortex. These episodes typically last 20 to 60 minutes and can occur with or without an accompanying headache.
The visual patterns vary widely. A systematic review of migraine aura symptoms found the most commonly reported were zigzag or jagged lines (24 to 81% of sufferers), blind spots (23 to 77%), small bright dots (19 to 70%), and white spots (7 to 22%). Some people also see colored dots, black spots, or a shimmering effect like looking through heat waves. These spots and patterns affect both eyes simultaneously and move with your gaze rather than drifting independently, which distinguishes them from floaters.
Diabetic Retinopathy
Diabetes can damage the tiny blood vessels that nourish the retina. In the early stages, the vessel walls weaken and develop small bulges that can leak fluid and blood into the retina. In more advanced stages, the eye attempts to grow new blood vessels to compensate, but these replacement vessels are fragile and bleed easily.
When blood leaks into the vitreous, it shows up as a few dark spots or, in more severe cases, large dark streaks or clouds across your vision. A small bleed might look like a sudden scattering of new floaters. A larger one can block vision significantly. Anyone with diabetes who notices new spots or a sudden increase in floaters should treat it as urgent, since early treatment can prevent permanent vision loss.
Inflammation Inside the Eye
Uveitis, inflammation of the inner structures of the eye, can also produce spots in your vision. When inflammation affects the middle or back of the eye, white blood cells and inflammatory debris collect in the vitreous. These cells float in the same gel that produces ordinary floaters, but the underlying cause is an immune response rather than normal aging.
In some cases, the inflammatory material clumps into larger collections sometimes called “snowballs” that are visible during an eye exam. Uveitis-related floaters are often accompanied by blurred vision and, depending on which part of the eye is inflamed, may or may not involve pain or redness. Uveitis can be triggered by infections, autoimmune conditions, or sometimes has no identifiable cause.
When Spots Signal an Emergency
Most floaters are benign, but certain patterns demand immediate attention. The warning signs to watch for are:
- A sudden shower of new floaters, especially dozens appearing at once rather than one or two
- Flashes of light that persist or intensify, particularly in your peripheral vision
- A dark shadow or curtain creeping across any part of your visual field
- A rapid loss of peripheral or central vision
These symptoms can indicate a retinal tear or retinal detachment. When the vitreous pulls away from the retina during a PVD, it can sometimes tug hard enough to rip the retinal tissue. A tear allows fluid to seep behind the retina and peel it away from the back of the eye. The “curtain” effect people describe is the detaching retina losing its ability to send visual signals. This is a time-sensitive emergency because a full detachment can cause permanent vision loss if not treated within hours to days.
Less Common Causes
A condition called asteroid hyalosis produces tiny, glittering yellow-white particles inside the vitreous. Under direct light, these look like stars in a night sky. Despite their dramatic appearance during an eye exam, most people with asteroid hyalosis don’t notice significant vision changes, though some do develop floaters from the crystals.
Other less frequent causes include bleeding from a blood vessel not related to diabetes (from high blood pressure or a blood clotting disorder, for example), eye injuries that disturb the vitreous, and previous eye surgeries that change the structure of the vitreous gel.
Treatment for Persistent Floaters
Most floaters fade in visibility over weeks to months as your brain learns to filter them out, and as the clumps settle lower in the eye. For people whose floaters remain disruptive, two treatment options exist, though neither is routine.
Laser vitreolysis uses targeted laser pulses to break apart large floaters. It’s safe, with no recorded complications in follow-up studies, but its effectiveness is limited. In one study, only 38% of patients found it moderately improved their symptoms, while 61.5% reported no improvement at all. It works best for a single, well-defined floater rather than scattered small ones.
A surgical procedure called vitrectomy, which removes the vitreous gel entirely and replaces it with a saline solution, resolves symptoms in about 93% of cases. However, it carries real surgical risks, including retinal detachment in a small percentage of patients. Because of this, it’s generally reserved for people whose floaters significantly impair daily life and who haven’t responded to laser treatment.