Eye floaters and flashes

Floaters are small dots, threads, rings or cobweb shapes that seem to drift in front of your eye. They move when your gaze moves. They are easiest to see against a bright sky or white wall. They come from the vitreous, the clear gel that fills the back of the eye. With age the gel becomes more liquid and tiny fibers clump together, casting shadows on the retina. Floaters are more common with age, in people who are nearsighted and after cataract surgery. They rarely harm vision, and the brain usually learns to ignore them.

Flashes look like sparks, arcs of light or brief lightning streaks, usually at the side of your vision. They stand out more in the dark. They happen when the vitreous pulls or rubs on the retina. The retina cannot feel pain, so it responds to this kind of tug by sending a signal of light. A common cause of both floaters and flashes is posterior vitreous detachment, in which the aging gel shrinks and separates from the retina. Usually this is harmless, but sometimes the pull tears the retina. A migraine aura is different: it usually looks like zigzag lines or a shimmering patch that spreads slowly and lasts many minutes, often up to about an hour, with or without a headache. A retinal flash is usually very brief and affects one eye.

Old floaters that stay the same for months or years are usually not a concern. The risk rises when something changes suddenly, because that is how a retinal tear can start. An untreated tear can lead to retinal detachment. Get an urgent eye exam the same day if you notice: a sudden shower of new floaters or a dark cloud; new flashes or flashes that keep coming back; a shadow, curtain or gray veil over part of your vision; a sudden drop in vision; or new floaters or flashes after an eye injury or eye surgery. Even after a normal exam, return if symptoms change, since a tear can appear weeks later. Only an exam can tell whether there is a tear.

Diagnosis is made by an eye doctor. Drops are used to widen the pupils, and after a short wait the doctor examines the vitreous and the entire retina with a slit lamp and special lenses. Dilation matters because tears are often in the far edges of the retina. If the vitreous is very cloudy, for example from bleeding, an eye ultrasound may be needed. Vision stays blurry for a few hours afterward, so avoid driving.

When the exam is normal and there is no tear, most people need no treatment. Floaters usually bother people less over time. No drops, pills or exercises have been shown to remove floaters. If a retinal tear is found, it is usually treated with laser or freezing around the tear to form a scar that seals the retina and lowers the risk of detachment. When floaters themselves are dense and seriously interfere with daily life over a long period, a vitrectomy may be considered. It removes the vitreous gel. It is the most effective way to clear floaters, but it is real surgery with risks such as cataract, infection and retinal tear or detachment, so it is reserved for selected cases after a detailed discussion.

Two very different lasers are involved. The first is retinal laser, a standard, well established treatment used to seal a tear found on exam. It does not remove floaters; it protects the retina. The second is YAG laser vitreolysis, which aims to break up large clumps in the vitreous or move them out of the line of sight. It is offered only in some centers and for selected cases, such as a single large, well defined clump at a safe distance from the lens and retina. Evidence is still limited, it does not suit most floaters, and it has its own risks. Ask your eye doctor whether it fits your situation.