How wearing contact lenses all day can destroy your eyesight

Aimee McWilliams, 33-year-old fashion designer from London had never experienced any problems with them. However Aimee, like many people, had been wearing them for much longer - in her case, for more than 14 hours every day. 

This had slowly been starving her eyes of oxygen; while the damage wasn't apparent to the naked eye, it was spotted when the optometrist used a special microscope. Aimee was shocked to learn that she was in serious danger of losing her sight.

Aimee said 'I was horrified,' 'I'd always worn my lenses from 7 am until nearly midnight. Nobody had told me that I was jeopardising my sight by wearing them for so long, though I suppose I just said I used them daily. 

'What frightened me even more was that there had been no signs anything was wrong, my eyes looked the same. And I'd delayed my annual check-up by several weeks because I was so busy and I didn't think I really needed one.'

Aimee McWilliams

Around 3.7 million people in Britain wear contact lenses. But many don't appreciate how meticulous you need to be about using them, says Hosam Kasaby, a consultant ophthalmic surgeon at Southend University Hospital and BMI Southend Hospital.

One of the risks is corneal neovascularisation, the condition Aimee had. As Mr Kasaby explains: 'The cornea - the clear outer layer at the front of the eyeball - is the only part of the body that gets its oxygen supply directly from the air rather than from the blood.

'But a contact lens acts as a barrier to that oxygen supply, so extensive wear can potentially starve the cornea of oxygen.

'The body compensates for this by growing new blood vessels over the cornea to provide an oxygen supply, or corneal neovascularisation. 

'Left unchecked, the eye can become covered with blood vessels, and turn the cornea opaque. In rare cases it can threaten sight.'

The problem is the condition can build up over several years - it's only when it gets to an advanced stage that contacts wearers become aware of a problem, as that's when it will cause red, irritated eyes, by which time it may be too late.

Stopping wearing the lenses can cause the new blood vessels to collapse, though in severe cases, when there is excessive blood vessel growth, even if they collapse, they can cause scarring.

Corneal neovascularisation may be more common with standard soft lenses, which are made of water-containing plastic. The other main type of lens, gas permeable, while less flexible, allows in more oxygen, says Robert Glass, a Manchester-based optometrist.

'There are also newer types of soft lenses, known as silicone hydrogels, which allow more oxygen to pass through to the cornea than previous soft lens materials, making them healthier,' he says.
There are lenses licensed for use during sleep, which are permeable enough to ensure there is minimal risk of corneal neovascularisation. But you should be assessed by an optometrist before using these.

It's not only corneal neovascularisation that's the problem with wearing contacts for too long. 

It's not only overuse of contact lenses that can threaten the health of the eye - carelessness with hygiene is an obvious problem. And, ironically, some patients think they are practising good hygeine but aren't, explains David Anderson, consultant ophthalmic surgeon and corneal specialist at University Hospital Southampton.

'Most people tend to wash their hands in the bathroom before putting in their lenses. But many are unaware that unless they dry their hands properly or if they leave their contact lenses uncovered in their case, they're potentially exposing themselves to a bug known as acanthamoeba. This lives in water tanks, which tend to provide the supply to bathrooms. As such it can be found on bathroom surfaces too.'

Acanthamoeba bugs stick to contact lenses and can then burrow their way through the cornea, causing acute pain. It's only at this stage that a sufferer would be aware they had a problem.

So how should you protect your eyes? Mr Kwartz recommends using daily disposable lenses, which are usually more expensive as each new lens will be sterile and will never need to be cleaned. 

If you do use monthlies - these are taken out and cleaned every night, and replaced after a month - rub them with the solution recommended by your optometrist before putting them in their case. 

The lens case should also be replaced every month, adds Mr Glass. 'Over time, cracks can form in which micro-organisms can thrive, leading to infection.'

And never reuse or top up disinfecting solution - put fresh solution in the case every time you take the lenses out, says Mr Glass. Rinse the storage case and leave it open to dry after use every day and clean it once a week with a clean toothbrush and contact lens solution.

But the most important thing is to try to limit lens use to eight hours a day and keep hands scrupulously clean, says Mr Kasaby. 

'Break the habit of wearing lenses from the moment you wake up until you go to bed - when you get home from work, switch to glasses in order to allow the eye's oxygen intake to get back to  normal. Or, if you have a social event, do this the other way round.'

The general advice is to avoid wearing contacts for more than eight hours a day.

Source: UK Dailymail

Edited by Uchenna Udekwe