Nine in 10 contact lens wearers choose soft lenses over hard ones because they are more comfortable. But they open themselves to a higher risk of eye infections.

RISKS OF SOFT LENSES

• Oxygen does not pass through the hydrogel material of soft lenses as easily as it does
  through hard lenses. This is not good as the cornea needs oxygen to stay healthy.
• The larger size of soft lenses presents a bigger barrier hindering oxygen flow to the cornea.
• Soft lenses are porous to fumes and chemicals and tend to retain them.
• They draw fluid from tears to retain their shape so they tend to dry the eyes faster. This
  makes eyes more prone to infection as tears help to wash bacteria away.

Dealer Daniel Ng, 28, discovered the price of looking good in March this year.  He had worn his coloured contact lenses - which made his eyes an attractive blue - for almost 14 hours.  After removing them, he found his eyes uncomfortably dry. But he did not count on waking up to a less-visible world the next morning.  He recalled: 'My left eye wouldn't open. It was bloodshot and painful when I tried to open it. I went to work that day with one eye closed.'  His manager told him to take the day off, so Mr Ng went to the Singapore General Hospital, which hospitalised him for three days.  Tests showed that it was likely he had picked up the bacterium pseudomonas aeruginosa from his soft contact lens. It caused an infection in his cornea which, if left untreated, could have covered the cornea and made him go blind.

This same bacterium was found in counterfeit coloured contact lenses seized by the Health Sciences Authority two months ago. The drug licensing body took away more than 100 boxes of fake 'FreshLook ColorBlends' lenses from five optical shops, which are being investigated.
Mr Ng needed antibiotic eyedrops for a month or so till the infection cleared.  But even genuine lenses do not guarantee a zero infection risk. 

All contact lens users are putting themselves at an increased risk of complications simply by using them, doctors say.  Studies have shown that an infection in the cornea affects about five out of every 10,000 contact lens wearers per year and those wearing soft contact lenses are at higher risk than those using hard ones.  It is a risk that thousands run every day. Global research company GfK reported last Friday that nearly 11 million contact lenses worth $34.7 million were sold in Singapore in the first six months of the year.  About a quarter were cosmetic coloured lenses, which anyone can wear even if they do not need vision correction. 

While they are convenient, contact lenses are essentially foreign objects worn on a sensitive part of the body. They reduce the amount of oxygen received by the eyes and increase the risk of micro-abrasions on the corneas, which then allow germs to thrive and infections to set in.

Dr Lim Li, a senior consultant ophthalmologist at the Singapore National Eye Centre (SNEC), said: 'There is no such thing as the safest lens. Contact lenses are regarded as medical devices and wearers must be committed to following the instructions taught to reduce their risk of eye infections.'

Contact lens infections will usually result in pain, redness, blurred vision, tearing and a white spot on the cornea.  In the case of an aggressive bacterium like pseudomonas, the spot can grow from under 1mm to 5mm - which covers the entire cornea - within 24 hours of the infection setting in, said Dr Lim.  Though rare here, it is a severe complication which can cause blindness or make a corneal transplant necessary.

Dr Cheryl Lee, an ophthalmic surgeon at Pacific Healthcare Specialist Centre, said that prior to the widespread use of contact lenses, corneal trauma and pre-existing ocular disease were the main causes of corneal infections.

From July last year to last month, 58 patients treated by SNEC doctors had to be hospitalised at Singapore General Hospital for corneal infections. All had worn soft contact lenses.  This is not surprising, said Dr Lim, given that 90 per cent of the world's contact lens wearers use soft lenses, which are easier to adapt to and, hence, more comfortable to use.  The trouble is, they are also more likely to give rise to infections than rigid gas permeable hard lenses, which are safer but far less popular because they are not as comfortable.

An Australian study published in the American Academy Of Ophthalmology in 2008 showed that the incidence of infective keratitis - corneal infection by micro-organisms - associated with daily wear hard lenses was 1.2 per 10,000 wearers per year.  This shot up to 1.9 per 10,000 for daily wear soft lens wearers and two per 10,000 for daily wear disposable lens wearers.

TEARS PROTECT THE EYES

The tears in a person's eyes contain anti-bacterial properties and the eyelids generally act as windscreen wipers to keep out infections, said Dr Ray Manotosh, a consultant from the department of ophthalmology at National University Hospital.  This is why there is very little chance of bacteria accumulating in healthy eyes to result in infections, he said.  But contact lenses disturb the film of tears as they are placed directly in it. Underneath the lens, the eye dries out and is unable to wash bacteria away efficiently.  When a contact lens rubs against the cornea or if a wearer scratches the cornea while taking out or putting in the lens, the resulting abrasions invite infections from bacteria, fungi and parasites.  In addition, contact lens wearers may become less sensitive to tiny abrasions on their corneas because they touch them so frequently, said Dr Lee.  The rigidity of hard lenses does not increase one's risk of corneal abrasions as the inside surface of such a lens is smooth, said Dr Stan Isaacs, president of the Singapore Contact Lens Society.

INNOVATIONS IN SOFT LENSES

Another problem for lens wearers is that insufficient oxygen reaches the surface of the eye.
Oxygen is needed by the cornea to keep it healthy and to promote the healing of abrasions.
Dr Isaacs said the silicone acrylic material of hard lenses allows oxygen to pass through more easily than the hydrogel material of soft lenses.  And while soft lenses are porous to fumes and chemicals and tend to retain them, hard lenses allow only gases to pass through but not liquid contaminants such as those from hand creams, chillies and onions, he added.  Dr Ray said the larger size of soft lenses, which cover the whole cornea, also creates a bigger barrier to oxygen permeability.
Hard lenses also tend to move more on the cornea with every blink of the eye. This is better because it allows all areas of the cornea to be exposed to oxygen once in a while, he said.
Silicone was added to soft lenses about 15 years ago to form silicone hydrogel lenses which allows more oxygen through, he said.  But it is doubtful if the innovations in soft lenses have made any difference.

The Australian study in 2008 found that new lens types did not reduce the incidence of contact lens-related or corneal infections in Australia.  The authors even noted that the use of silicone hydrogel contact lenses carried a higher risk of infection than that of hydrogel contact lenses, possibly because of 'factors intrinsic to the material properties of these contact lenses'.

Dr Voon Li Wern, an ophthalmologist in private practice at Parklane Shopping Mall, said that even though soft lenses allow more oxygen through now, they will always dry the eyes faster than hard lenses.  This is because soft lenses draw fluid from the film of tears to retain their shape, unlike hard lenses which keep their shape all the time, she explained.

After his eye scare, Mr Ng is sticking to a disciplined regimen of wearing his daily disposable lenses - and not coloured lenses - for eight hours at the most.  Next month, he hopes to go for an eye examination to assess his suitability to undergo Lasik, an operation to reshape the cornea to improve visual acuity.  He said: 'I want to get rid of contact lenses for good.'