FLOATERS AND FLASHES – THE INSIDE STORY

Do you ever experience specks, threads or cobwebs in your line of vision, only to see them disappear when you try to focus on them? Or do you see flashes of light or sparks flickering across your field of vision when there is nothing there? Both of these are common occurrences for many people, and, although they may be irritating or alarming, they are usually harmless. Although they seem to be outside the eye, they are actually coming from within the eye itself.

FLOATERS, FLASHES AND HALOES

Floaters are a common complaint, as are flashes, but to a lesser extent. The two may occur separately or together, depending on the underlying reasons. Haloes are less common.

The small specks or threads drifting in the line of vision are called floaters. They may have different shapes, which move as the eyes move, and drift slowly when the eyes are still. Floaters are actually tiny clumps of gel floating inside the vitreous humor, the fluid that fills the inside of the eye.

The vitreous humor is a clear jelly-like fluid with the consistency not unlike raw egg white. It fills the rear two thirds of the eye, providing a pathway to the back of the eye for light entering through the lens. It is contained within a fine membrane attached to the lens at the front of the eye and the retina at the back. As we age, the vitreous gel starts to thicken, shrink or become stringy, forming clumps or strands that move inside the eye. What we see is not the floater itself, but the shadow it casts on the retina.

In some cases, the retina can tear as the shrinking vitreous gel pulls away from the wall of the eye. A torn retina can lead to a retinal detachment, which is a potentially serious problem that needs to be attended to as soon as possible.

Experiencing flashes in the eye, often at the edges of vision, is fairly common. Flashes can vary from a bright light to almost a sparkle, and last a varying length of time. As the shrinking vitreous gel pulls or bumps against the retina at the back of the eye, signals are sent to the optic nerve which transmits them to the brain. The brain interprets the signal as light even though there is no external light present, and the stimulus is coming from within the eye.

Eventually the vitreous tends to pull right off the retina, a condition called posterior vitreous detachment. This condition is not harmful to the eye or vision, and happens to most people as they age, but occasionally it can cause the retina to tear. Increasing, persistent, constant or sudden appearance of flashes may indicate that the retina is at risk of tearing or has been torn or detached. Visit your optometrist immediately, as this could be serious and needs to be managed as soon as possible.

Although not strictly flashes, some people experience what is known as pseudoflashes. These may include photophobia (extreme sensitivity to light) and glare. Some people who suffer with migraines experience flashing lights in the eye. Usually, in the case of migraines, these occur in both eyes at the same time. They can last up to an hour and tend to increase to a maximum before fading away and being replaced by a headache.

Haloes are rainbow-like coloured rings around lights or bright objects. They usually occur because there is extra water in the layers of the eye, due to excessive tears, overuse of contact lenses, cataracts, chronic glaucoma or side effects of some medications. A potentially serious cause of haloes is acute glaucoma, a condition which usually occurs suddenly and is characterised by increased pressure in the eye. This is a painful condition which can threaten sight if not treated promptly.

Although haloes are common and not harmful to vision, they can be uncomfortable and unpleasant. Night driving can be stressful and difficult, because of the halo effect on street lights and the lights of oncoming cars.

CAUSES AND RISK FACTORS

As discussed, changes in the vitreous humor due to the aging process are the most common cause of floaters and flashes. Other risk factors include inflammation in the eye, diabetic eye disease, and recent eye surgery. People who are very shortsighted are at a greater risk for developing floaters earlier than normal, and for retinal tears or detachment. Floaters will result from any internal damage to the back of the eye. Retinal tears and retinal detachments will also cause floaters and these will vary in severity depending on the severity of the damage.

WARNING SIGNS OF PROBLEMS

Sometimes floaters and flashes signal a condition that can lead to vision loss. Retinal tears and detachments are painless, but certain warning signs indicate that you should consult your optometrist as soon as possible. These include a new and sudden onset of floaters or flashes, gradual shading of vision from one side, changes in vision, or a sharp decline of central vision. The earlier a retinal tear or detachment is detected, the earlier it can be treated, and the more positive the outcome is likely to be.

TREATMENT

While most floaters and flashes are not serious, a regular eye examination is advisable to make sure there is no retinal damage and to check the pressure in the eyes. The treatment will depend on the underlying condition, if there is one. There is no specific treatment for the separation of the vitreous gel from the retina, but surgery or laser therapy may be required for retinal detachment or tears.

LIVING WITH FLOATERS

If your floaters aren't a sign of retinal damage, they may disappear, become less noticeable, or stay and become irritating. Floaters can be removed, but for most people the risk to vision from the surgery is greater than the problem posed by the floater. If floaters become a nuisance, move your eyes up and down or left to right – this should provide temporary relief by shifting the floater.

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