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Ablatio corporis vitrei posterior
The commonest reason for flashes — and the moment when a retinal tear can occur. The detachment itself is harmless; the examination of the back of the eye is not.
Also known as: posterior vitreous detachment · PVD · flashes and floaters
Open in the tool — with search and all the links →This compilation is for information and replaces neither medical diagnosis nor treatment. If you have symptoms, see a doctor.
The vitreous fills the eye behind the lens. It is a clear gel, and it liquefies over the years. At some point it collapses and separates from the retina it was lying against — usually between fifty and seventy, earlier in short-sighted people and after cataract surgery. This is not a disease but a process almost everyone who lives long enough goes through.
Two things get noticed. First floaters: threads, flakes, a ring or a cobweb that travel with the gaze and come to rest a moment late. Second flashes — brief bright arcs, mostly at the outer edge of the visual field, clearest in the dark and when the eyes move. These flashes do not come from light: as it separates, the vitreous pulls on the retina, and the retina cannot tell pull from light. It reports what it always reports.
The process itself needs no treatment. The flashes grow rarer over weeks to months; the floaters stay but become less noticeable with time. The significance lies elsewhere: where the vitreous is especially firmly attached, it can tear a hole in the retina as it comes away. In about one in ten people with fresh flashes and floaters such a tear is found — and a tear that is known about is ringed with a laser in one sitting. A tear nobody has seen can lead to a retinal detachment.
So every freshly appeared episode of flashes or floaters belongs examined once, with the pupil widened and the view carried to the outermost edge of the retina. And because tears can still appear weeks later, this examination is usually repeated after four to six weeks.
Only a widened pupil shows the outermost edge of the retina — and that is exactly where tears sit. Usual window for flashes and floaters alone: within a few days. For a swarm of dots, a shadow or worsening sight: the same day.
Some tears do not appear at the first moment but in the weeks that follow. A clean first result therefore means "nothing now", not "nothing ever". That follow-up is why most detachments are avoidable.
Date, which eye, how many flashes, whether the floaters are increasing. It costs two lines and answers the first question any doctor asks — more precisely than memory can after a week.
The aura sits in both eyes — it does not vanish when one eye is covered —, shows zigzag lines or a shimmer, travels slowly across the field and is over in twenty to thirty minutes. Flashes from vitreous detachment are one-eyed, last an instant and come in the dark.
A short-sighted eye is built longer, the retina thinner and more vulnerable at the edge. The detachment comes earlier and tears are more common. Anyone strongly short-sighted should call rather than wait.
They sink out of the line of sight over time and become less noticeable, because the brain edits them out. That takes months. Procedures on the vitreous exist, but they are rarely considered and only for severe impairment, because they carry risks of their own.
Threads, dots, a ring or a cobweb. They move with the gaze and come to rest a moment later. Best seen against a bright even surface — a white wall, the sky, a screen.
Brief bright arcs or streaks, mostly at the outer field, often on eye movement and almost only in the dark or at dusk. They last a fraction of a second and repeat over days.
The process runs in each eye separately, usually months to years apart. Covering one eye at a time shows which it is. Both eyes at once points elsewhere.
Some see a distinct circle or an "O" that appeared overnight. That is the spot where the vitreous was attached at the optic disc — a sign that the detachment has happened.
A swarm of tiny dots, like soot or pepper, is no longer the ordinary detachment. It comes from blood in the vitreous, and blood usually means a vessel was torn along — in about half of those cases a tear lies behind it.
A dark curtain, a wall or a missing field at the edge that grows over hours does not belong to this. That is the sign of retinal detachment and counts in hours, not days.