Wednesday, January 18, 2012

Contact lens FAQs

Problems such as shortsightedness have become so common in Singapore that by 12 years of age, about 60% of children are already wearing glasses. Although spectacle wearing is effective and safe, they are not always the most convenient of things to use.

At my clinic, we often come across patients who are either keen to start wearing contact lenses or are already wearing them but have some nagging questions about them that they just thought of. Hopefully this post, which is in a Q+A format, will help to answer those queries.
  1. Can my contact lenses get lost in my eyes?
Contact lenses cannot be lost in the eyes, because there are natural pockets at the side of the eyes which prevent the lenses from going further backwards. However, they may sometimes slip off the cornea onto the white part of the eye. If this is noticed, you may reposition it yourself, or see an eye care professional for help.
  1. If I’m playing soccer and the ball hits me near or on my eye, will my lenses break or tear in my eyes?
Direct impact by the soccer ball onto the eyeball will cause injury of varying severity depending on the force of the trauma. A soft contact lens will not generally break or tear due to its flexibility. A hard contact lens could theoretically break although that is also very unlikely due to the softness of the surrounding tissues. What happens more commonly is the lens is knocked or rubbed off the eye. Surface abrasions of the cornea may be caused as a result.
  1. I want to wear coloured lenses to look different sometimes... Will these lenses damage my eyes?
Coloured or tinted lenses are available from major manufacturers such as Cibavision. These are generally safe to use but like all contact lenses should be dispensed only after fitting by an eye care professional. Buying these lenses from internet sources, or from manufacturers with an unknown reputation risks severe damage to the eye from problems such as infection, irritation from chemicals in the soaking solution, or poorly fitting lenses.
  1. I heard that I could catch Acanthamoeba infection by swimming without removing my contact lenses. This parasite can burrow into my eyes and make me blind. Is this true?
Acanthamoeba is a one-celled protozoan parasite that is found in many places in our environment, including tap water. If contaminated water from the swimming pool enters the eye, Acanthamoeba can stick to the contact lens and establish an infection on the surface of the eye. If not treated, a severe corneal ulcer can develop causing blindness. In general contact lenses should be removed before swimming and they should not be cleaned with tap water or home made saline to avoid this infection.
  1. I have no access to saline solution and even tap water. There is a problem with one of my lenses (the edge has curled inwards slightly and is causing me pain). What can I do? Can I remove the affected lens and re-wet it with saliva?
The best thing to do is to remove the contact lens and discard it. Saliva should not be used because the mouth is filled with bacteria and using saliva is going to contaminate the lens, thereby making it very likely for a corneal infection to occur.
  1. I fell asleep overnight with my lenses on. Will they get stuck to my eyes?
Sleeping with contact lenses on for any length of time raises the risk of infection and should not be done for any length of time. Even without an infection, lens adherence or sticking to the eye is very common after sleeping with them on and is due to a combination of dryness and the pressure of the eyelids. This sticking is not permanent, and if it happens, the wearer should wet the eyes with re-wetting solution or artificial tears, and then attempt to remove the lens after a few minutes. If this cannot be done, then an eye care professional should be consulted for removal of the lens.
  1. I use daily disposables. However, I’ve been wearing them continuously for a week (I don’t remove them). How long can I overuse disposable lenses?
It is very dangerous to wear daily disposable lenses in such a fashion. The lenses become coated with deposits and sooner or later an infection develops or the eye becomes red and irritated from the lack of oxygen and deposits. Disposable contact lenses should be changed strictly according to the schedule recommended by the manufacturer.
  1. I was travelling overseas when I ran out of saline solution. I used tap water to rinse my lenses instead. After a few days, I started noticing coloured spots on my lenses. What is happening to my lenses?
It is not possible to say with certainty what these spots are but they could be mineral deposits if the tap water was hard (with a high concentration of dissolved substances). Worse, they could even be fungus growing on the contact lens. These lenses should be discarded immediately.
  1. Do the new “HD” soft lenses work for people with astigmatism? Can people with severe astigmatism wear such “HD” lenses? Are RGP lenses still preferred for people with astigmatism?
“HD” refers to optimized optics which include aspheric designs but it does not necessarily mean that the lens will have a toric component to correct astigmatism. A person with severe astigmatism needs either a toric soft lens or a rigid gas permeable (RGP, otherwise known as hard) lens. RGP lenses correct astigmatism very well and possibly provide the sharpest vision among the types of contact lenses. However this must also be balanced with comfort issues.
  1. I have lazy eyes. Will contact lenses help my condition? What types of contact lenses are best suited for my condition?
Lazy eyes (amblyopia) develop during childhood because a disturbance of vision prevents normal development of the nerve pathways between the eye and brain. Later on in life, vision remains blurred in the lazy eye even when glasses or contact lenses are worn, because the problem has to do with the nerves and brain, and is not related only to spectacle power. If lazy eyes are detected in childhood, the better eye is patched and the child is forced to use the lazy eye to see, with the use of glasses or contact lenses as appropriate. Beyond the age of about 10 years, patching is no longer useful. Older children and adults with lazy eye are now treatable with a revolutionary computer based training program called Neurovision (see This presents customised images to the patient and over a period of several months improves nerve connections and vision even in adults with lazy eye. As such, lazy eyes are not treated by particular contact lenses per se, but the contact lenses or glasses will help with any long/short-sightedness or astigmatism that is present.


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