Eye floaters and flashes: what you need to know

You are reading, or looking out of a window, and something drifts across your vision. A small dark speck. A thread. A cobweb that seems to float just ahead of wherever you look. You move your eyes to focus on it and it slides away.

For most people, the first time this happens it is unsettling. The instinct is to wonder whether something is wrong. In the majority of cases, it is not. But there are situations where floaters, and particularly flashes of light, are a signal that needs prompt attention. Knowing the difference matters.

What are floaters?

Floaters are shadows cast on the retina by tiny clumps or strands within the vitreous, the gel-like substance that fills the inside of the eye. They are not on the surface of your eye, which is why blinking does not make them go away, and they are not on your glasses, which is why cleaning the lenses does not help either.

They appear in many forms. Small dots. Rings. Threads or wispy strands. Some people describe them as looking like a hair floating in their vision. Others see something that resembles a small insect or a piece of lint. They tend to be most noticeable when you look at a plain, bright background: a white wall, a pale sky, a lit screen.

They move when your eye moves, and they drift lazily when your eye is still. That drifting quality is one of the things that distinguishes them from other visual disturbances.

Why do they appear?

The most common cause is a natural change in the vitreous gel that happens with age. Over time, usually from the mid-40s onwards, the vitreous gradually liquefies and can shrink slightly, pulling away from the back of the eye. This is called a posterior vitreous detachment, and it is extremely common. As the gel changes, small fibres within it can clump together and cast shadows on the retina. These shadows are what you see as floaters.

A posterior vitreous detachment is not a disease. It is a normal part of ageing and most people who experience it never have any complications. The floaters it causes often become less noticeable over time as the brain learns to filter them out.

Floaters can also appear after eye inflammation or injury, and they are more common in people who are short-sighted, as the eye is slightly longer and the vitreous can change earlier. But the vast majority of new floaters in adults over 40 are the result of this same natural process.

What about flashes of light?

Flashes are different from floaters, and they are important to understand separately.

When the vitreous pulls away from the retina, it can tug on it. The retina interprets that tugging as light, which is why you might see brief flickers or flashes, usually in the periphery of your vision, even in a dark room. These flashes are particularly common when the vitreous is in the process of detaching, and they can occur alongside new floaters for the same reason.

In most cases, flashes associated with a posterior vitreous detachment settle down within a few weeks as the vitreous fully separates. But flashes can also be a warning sign that the retina itself has been pulled or torn during the detachment process. A retinal tear, if not treated promptly, can lead to a retinal detachment. That is a serious condition that can cause permanent vision loss.

This is why flashes always warrant attention, even if they seem brief or minor.

When should you be seen urgently?

Most floaters do not require emergency attention. But certain symptoms are a clear signal to get seen the same day rather than wait for a routine appointment.

Contact your optician promptly, or go to an eye casualty unit, if you experience any of the following:

• A sudden shower of new floaters, many more than you have had before, appearing quickly
• Flashes of light, particularly if they are new, frequent, or persistent
• A shadow, curtain, or dark area appearing at the edge of your vision
• A grey or dark veil that seems to be spreading across part of your visual field
• A sudden significant change in your central vision

Any of these could indicate a retinal tear or detachment. Time matters with retinal detachments. The sooner they are treated, the better the outcome. This is not a situation to monitor and see how it goes.

If you are ever unsure, it is always better to get checked and be reassured than to wait.

When are floaters nothing to worry about?

If you have had the same floater or floaters for months or years and nothing has changed, they are almost certainly benign. Long-standing floaters that have been stable are a normal finding and do not require urgent investigation.

If you are in your 40s or older and notice a new floater, particularly a single cobweb or strand with no flashes or other symptoms, it is still worth mentioning at your next eye test. In many cases, it will not represent anything serious.

The honest answer is that most floaters are an inconvenience rather than a threat. They can be frustrating, particularly if they sit in your central vision and make reading or screen work harder. For the vast majority of people, the brain gradually learns to ignore them, and they become much less intrusive over time.

Can floaters be treated?

For most people, no treatment is needed or recommended. The floaters become less noticeable with time, and the risks of any intervention outweigh the benefit for routine cases.

In a small number of cases where floaters are severely affecting quality of life, particularly if they are large, dense, or sitting centrally in the vision, there are procedures available. Laser vitreolysis uses a laser to break up floaters, and vitrectomy surgery removes the vitreous gel entirely. Both carry risks and are generally considered only when floaters are causing significant, lasting difficulty. These are not routine treatments and are not available on the NHS for straightforward age-related floaters.

If floaters are genuinely affecting your daily life, it is worth discussing this with your optician so the options can be explained properly in the context of your specific situation.

What should you do if you notice floaters for the first time?

The most sensible step is to have your eyes examined. An optician can dilate your pupils and examine the vitreous and retina properly, giving a clearer picture of what is happening and whether anything needs follow-up. Our guide to what happens during an eye test explains the wider examination process step by step.

If your floaters came on suddenly or are accompanied by flashes, do not wait for a routine appointment. Get seen the same day. If they are new but without other symptoms, booking an appointment within the next few days is reasonable.

Regular eye tests remain important even when your sight feels normal, because an examination assesses the health of the retina and other structures as well as your prescription. If your optician has previously noted a stable posterior vitreous detachment, floaters similar to those you have experienced before may be less concerning, but any definite change should still be checked.

At Iology in Barking, we can examine the back of your eye thoroughly and explain clearly what we find. If you have noticed something new in your vision, or an existing floater has changed, book an eye test rather than spending days worrying about it.

You can also read our guide to what happens during an eye test before your appointment.