Almost everyone eventually notices a few drifting specks or threads against a bright sky or a white screen. They are usually harmless, and they come from a part of the eye most people have never heard of.
The vitreous is the clear gel that fills the large chamber behind the lens. It changes over a lifetime, and the way it changes explains both the ordinary floaters you can safely ignore and the sudden ones you cannot.
Knowing the difference is genuinely worth a few minutes of reading, because one version of this is an urgent appointment.
The gel in the middle of your eye
The vitreous takes up most of the volume inside the eyeball, filling the space between the lens at the front and the retina lining the back.
It is mostly water. What makes it a gel rather than a puddle is a loose mesh of collagen fibers held apart by long sugar molecules that trap water between them. That structure has to be optically clear, because every bit of light reaching your retina passes through it.
Two things make the vitreous unusual. It has no blood supply of its own, and unlike the tears or the fluid at the front of the eye, your body does not replace it. The gel you were born with is the gel you keep.
What it does all day
- Holds the eye's round shape from the inside, keeping the retina pressed smoothly against the back wall
- Provides a clear, undistorted path for light between the lens and the retina
- Cushions the delicate tissues against everyday knocks and head movement
It is also lightly attached to the retina in places, most firmly around the optic nerve, near the macula and at the far edges. Those attachment points are where the interesting problems begin.
Why it turns liquid with age
Starting in early adulthood and picking up pace over the decades, the collagen mesh begins to clump together and pull apart. Pockets of watery fluid form where firm gel used to be. The clumped strands are no longer perfectly clear, so they cast faint shadows on the retina, and you see those shadows as floaters.
Floaters drift when your eye moves and settle when it stops, which is why they slide away when you try to look straight at one. Plain backgrounds and bright light make them obvious.
The process runs earlier in people who are significantly nearsighted, and it can be sped up by eye injury, inflammation inside the eye, or previous eye surgery such as cataract removal.
Posterior vitreous detachment
Eventually enough of the gel liquefies that the shrinking body of it peels away from the retina at the back. That is a posterior vitreous detachment, and it is a normal event, most often in the fifties, sixties and seventies. Many people go through it without any drama.
When it does announce itself, it feels like this: a sudden increase in floaters, sometimes a whole shower of specks, sometimes one large ring or cobweb that follows your gaze. Flashes of light often come with it, usually brief arcs at the edge of vision, most noticeable in a dark room. The flashes come from the gel tugging on the retina, which the retina can only interpret as light.
In most people the symptoms calm down over weeks to a few months as the gel finishes separating and the brain stops paying attention to the remaining floaters. The problem is that as the gel peels, it can pull hard enough at an attachment point to tear the retina, and a tear can let fluid underneath and lift the retina off. That is a sight-threatening emergency, and it cannot be told apart from an uncomplicated separation without an examination.
Which floaters need a same-day call
Floaters you have had for years, that have not changed in number or behavior, are not an emergency. They are annoying, and most people gradually stop noticing them.
Contact an eye doctor the same day, or go to an emergency department if you cannot reach one, for any of these:
- A sudden burst of new floaters, or a noticeable jump in how many you see
- Flashes of light, arcs or sparks, especially repeated ones or ones in a dark room
- A shadow, curtain or veil moving in from the side of your vision
- A sudden drop in vision, or a sudden haze like looking through smoke
- New floaters after a blow to the head or eye
- New floaters if you have diabetes, since bleeding into the gel is a possibility
Say clearly on the phone that you have new floaters and flashes. That phrasing is understood in every eye clinic, and it should get you seen quickly rather than booked for next month.
What the visit involves
Expect dilating drops. The doctor needs a wide view of the retina, especially the far edges where tears usually hide, and that cannot be done through a small pupil. The exam takes a while, bright light is involved, and your vision will be blurry for several hours afterward, so arrange a ride and bring sunglasses.
If everything looks intact, you will often be asked to return in a few weeks, because a tear can show up after the first exam. Go back if the symptoms get worse in the meantime. If a tear is found, it can usually be sealed in the office with laser or a freezing treatment before the retina lifts, which is precisely why speed matters.
Common questions
Will my floaters ever go away?
They rarely disappear, but they often sink out of the line of sight, and the brain learns to ignore them. Most people are far less bothered a year later.
Can drops or supplements clear floaters?
No. Nothing you can buy dissolves clumped collagen inside the eye. Be skeptical of anything sold on that promise, and talk to your doctor before adding supplements.
Do screens or reading cause floaters?
No. Screens do not change the gel. You simply notice floaters more against a bright, plain background.
Ordinary floaters are part of the eye aging quietly. New floaters with flashes are a different situation and deserve an exam that day, not a wait-and-see. If something has changed in the last day or two, look up eye doctors in your area who take your insurance and ask for an urgent dilated retinal exam.