Flashes harmless but may be warning signals

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FLASHES and floaters are harmless, but may warn of more serious issues.

Mdm Marilyn Tan, 60, had nothing wrong with her vision except that she was slightly short-sighted. But when she started seeing spots that persisted after three weeks, she got a little worried and made an appointment to see a specialist.

At the Singapore National Eye Centre (SNEC), Dr Loh Boon Kwang, Consultant, Vitreo-Retinal Service, Cataract and Comprehensive Service, found that the vitreous humour – a jelly-like liquid in her eye – had degenerated.

Dr Loh said that the condition, known as vitreous degeneration, is fairly common, and causes flashes and floaters – moving spots and light streaks in one’s field of vision. They are not usually a cause for worry, but can sometimes be indicative of a more serious condition.

Follow-up consultations confirmed that Mdm Tan was well and she was discharged, but Dr Loh advised her to watch for any signs of a retinal detachment. This is because flashes and floaters can indicate a more serious eye condition if the jelly-like liquid pulls more against the inside of the wall of the eyeball, where the retina (the eye’s light-sensing inner layer) is located. This can cause breaks or holes in the retina and detach it.

This happened to Mdm Cassandra Lee, 40. Also short-sighted to begin with, she had blurred vision in her left eye for a week before consulting Dr Loh. Examinations revealed that she had suffered a retinal detachment, which could lead to a partial or complete loss of vision. She had to undergo scleral buckling surgery, where the doctor puts a synthetic plastic belt-like device around the outside of the eyeball, to push the eyewall against the detached retina. The operation was successful and Mdm Lee’s retina was re-attached.

Dr Loh said flashes and floaters are part of ageing, so it is common for people aged 60 and above to have them – but younger people can get them too.

“Generally, the effects of flashes and floaters are the same in the initial phase for those in their 20s and 60s. It just means that the onset of vitreous degeneration can occur at different ages – the progression is about the same,” he said.

Over time, as the jelly-like liquid in the eye degenerates, the vitreous humour becomes smaller and forms tiny clumps of gel, casting shadows on the retina which appear as floaters. They are seen as small spots even when the eyes are closed, and are more obvious in bright sunlight or when looking at a white background.

Flashes – an illusion of flashing lights or lightning streaks – occur when the jelly-like liquid pulls on the retina, sending a signal to the brain, and making the person perceive a light flash. Flashes may appear on and off for several weeks or months. The symptoms decrease after a few months, so many patients get used to it. “But they know they are not cured of the flashes or floaters,” said Dr Loh.

Serious conditions such as a retinal tear or renal detachment can arise, if there is a sudden increase in flashes and floaters, and risk factors are present. These risk factors include ageing, short-sightedness of over 600 degrees, previous internal eye surgery, and a family history of retinal detachment, which may make structures in a person’s eyes more prone to retinal tearing, said Dr Loh.

Diabetics are also at risk of retinal detachment and diabetic retinopathy, where blood vessels in the retina weaken and bleed. When blood seeps into the jelly of the eye, it causes floaters.

Global studies show that one in 10,000 people in the general population suffers from retinal detachment. Also, one out of 10 patients with an acute increase in flashes and floaters, seen in the emergency setting, runs the risk of having a retinal tear or detachment, said Dr Loh.

Warning signs of a retinal tear or detachment include:

•  An acute onset of flashes and/or floaters, which develops suddenly within a few days or weeks.

•  Floaters appearing in the hundreds and thousands.

•  Blurred vision, or a curtain effect where the person sees shadows within his visual field.

There is currently no cure for flashes and floaters, and those who experience a sudden increase in them, or those most at risk of a torn retina, should seek medical attention early.

• Names of patients have been changed to protect their privacy.

• This story was first published in Singapore Health, Mar/Apr 2014.