A study published in January this year in American journal Eye & Contact Lens found that most people suffering from eye infections wore soft contact lenses.  Between April 1999 and March 2001, 93.7 per cent of lens wearers who sought treatment at public hospitals here wore soft contact lenses.  Of these, more than half wore soft disposable lenses. They made up the bulk of those suffering from the most common contact lens-related complication called infective keratitis, the authors noted.

Researchers collected data from 721 patients who were seen at Singapore National Eye Centre (SNEC), Singapore General, Tan Tock Seng, National University and Changi General hospitals for contact lens-related complications during this period.  A similar new study is currently underway to investigate if trends have changed, said Dr Lim Li, a senior consultant ophthalmic surgeon at the corneal and external eye disease service of SNEC, who was the principal investigator of the published study.

Based on that survey, here are the most common contact lens-related complications:

1. INFECTIVE KERATITIS

What: Inflammation of the cornea as a result of micro-organisms is the most common - and most severe - complication of contact lens use. In the survey, one in four lens wearers who were treated had such a condition. It is potentially sight-threatening even with successful treatment.
Causes: It is caused by micro-organisms such as bacteria, fungi and parasites. The most common micro-organism is pseudomonas aeruginosa.
Symptoms: They include pain, redness, blurred vision, white spot on cornea, tearing, photophobia (an abnormal sensitivity or intolerance to light) and mucus discharge.
Treatment: In severe cases, patients are hospitalised for treatment.  A corneal scrape may be done to culture the organism to identify it. Intensive antibiotics are used to control the growth of the white spot on the cornea and kill the micro-organism.  After treatment, scars may be left on the cornea. If they are located in the centre of the cornea, vision is permanently blocked, unless the patient undergoes a corneal graft or corneal transplant. 

2. EPITHELIAL KERATITIS

What: Corneal inflammation affecting the topmost layer of the cornea, called the epithelium, hit almost one in four lens wearers in the survey.  The most common type of this condition is punctate epithelial erosions, where there are small holes in the topmost layer of the cornea.
Causes: This is usually caused by abrasion of the cornea by ill-fitting contact lenses, or from prolonged wear and dry eyes.
Symptoms: They include blurred vision, red eyes and tearing.  There may be no symptoms, so it is important for contact lens wearers to go for regular eye check-ups to pick up this condition.
Treatment: Stop wearing contact lenses for a period of time.  Artificial teardrops will help. Antibiotic eyedrops may be prescribed to prevent corneal infections, as the holes make the eye susceptible to infections.

3. ALLERGIC CONJUNCTIVITIS

What: Allergic conjunctivitis, an inflammation of the conjunctiva - the transparent membrane which lines the eyelids - afflicted almost one in five patients.  The most common type of this condition is giant papillary conjunctivitis, a hypersensitive allergic reaction to the contact lens or its solution.
Causes: It is caused by repeated mechanical irritation of the conjunctiva from the use of contact lenses. Excess protein deposits on dirty lenses can result in this condition too.  Those who have a history of eczema, asthma or allergic rhinitis have an increased risk of developing it, as they have sensitive skin.
Symptoms: They include redness, eye irritation, a mucous discharge from the eye, inflamed bumps under the eyelids and eyelid swelling.
Treatment: Discontinue the use of lenses until the condition has resolved, which may take weeks.
This condition tends to be chronic, so patients may have a mild form of it persisting, but they may continue wearing their lenses.  Patients can also switch to wearing daily disposable contact lenses, which have minimal risk of deposits forming on them and do not need cleaning solutions.