I often see semi-transparent specs of stuff floating across my field of vision. They seem to be inside my eyes. Does this mean there is a problem with my eyesight? Should I be worried?
About eight out of 10 adults see similar things. Although people may describe them in different ways, they are generally known as "floaters."
In the vast majority of cases, they are no cause for concern and result from normal aging. For some individuals, however, floaters – especially when accompanied by brief flashes of light – can be signs of an underlying eye problem that needs medical attention.
Before going into further detail, it's worthwhile reviewing how the eyeball actually works.
Light enters through the cornea – the front window of the eye – and is focused by the lens on the retina at the back of the eyeball. The retina is made up of specialized cells that convert light into electrical signals, which are carried by the optic nerve to the brain for processing.
The retina functions like film in an old-fashioned camera before the days of digital photography. And the brain performs the role of a film-processing lab, converting the retina's signals into images.
The interior of the eyeball is filled with a colourless, transparent jelly-like substance called vitreous. When you are young, vitreous is fairly thick and has the consistency of Jell-O. As you age, it begins to liquefy, with some fluid pockets forming within the eyes.
Furthermore, some bits of the vitreous will clump together – and this is what causes floaters. When the tiny clumps pass in front of the light steaming into the eye they cast shadows on the retina, creating ghostly images of semi-transparent dots, lines and squiggles, explains Dr. Harmeet Gill, an ophthalmologist at Sunnybrook Health Sciences Centre and Mount Sinai Hospital in Toronto.
Floaters usually become more apparent when you're looking at a bright background such as the daytime sky. They even seem to dart about as they swish around in the partly liquefied vitreous gel.
Over time, the vitreous may condense further and can start to separate from the retina. That's when you can run into trouble. The sticky vitreous tends to pull on the retina and may create a tear or hole in the light-sensitive cells.
To understand this process, Gill says it helps to think of the retina as being like wallpaper lining the back of the eye and the vitreous acting like sticky fingers.
"As the sticky fingers tug on the wallpaper, they can create a tear in thin weak spots," Gill explains. The liquefied gel can then seep into the hole causing the retina to separate from the supportive tissue at the back of the eye. "It's like bubbles forming under the wallpaper," Gill adds.
This condition is known as retinal detachment and it could lead to permanent vision loss.
Fortunately, it can be fixed. But getting timely medical treatment is critical. That means you need to recognize the warning signs.
A sudden cascade of new floaters, plus the presence of quick flashes of light at the edge of your vision are two red flags that something might be seriously wrong. In particular, the flashes may indicate that the vitreous is tugging on the retina. "Ideally, the patient should be seen by a doctor within 24 to 48 hours," Gill says.
If the floaters and flashes are followed by what appears to be a dark curtain or shade being pulled across your vision, then head to the nearest hospital emergency department, Gill advises.
The "curtain" likely means there is already a tear and liquid vitreous is spilling behind the retina.
Surgeons can use several different techniques to patch the tear and press the retina into its proper place – firmly affixing it to the back wall of the eye. For instance, they might use a laser beam, an injection of specialized gases or a silicone band that temporarily wraps around the eye.
Although a retinal detachment can happen to anyone, some people are at greater risk of developing the condition, including those who are nearsighted, have had a previous eye injury or have undergone eye surgery. (Diabetics are also prone to vision problems – including bleeds in the eye – although the underlying cause is quite different.)
The good news is that a retinal detachment can usually be repaired and most people are left with only minor distortions in their overall vision.
Paul Taylor is a patient navigation adviser at Sunnybrook Health Sciences Centre. He is a former health editor of The Globe and Mail. You can find him on Twitter @epaultaylor and online at Sunnybrook's Your Health Matters.