Contact lenses: the habits that prevent an infection

Contact lenses are a well-established, safe way to correct vision. They are also a foreign object sitting on the cornea for many hours a day, and the cornea has no blood supply of its own — which means an infection there is harder for the body to fight and can scar permanently.

Almost every serious contact-lens complication traces back to a short list of avoidable habits. Here is the list.

The rule about water

Keep water away from your lenses. Not tap water, not bottled water, not sachet water, not boiled water, not saliva.

The reason is a microorganism called Acanthamoeba, which lives in ordinary water supplies and is essentially harmless to an intact eye — but which can infect a cornea that a lens has made slightly vulnerable. Acanthamoeba keratitis is intensely painful, difficult to treat, runs for months, and not infrequently ends in corneal scarring or transplant.

In practice this means: never rinse lenses or the case in water, never store them in water, never use saliva to wet a lens, and take lenses out before swimming or showering unless you are wearing sealed goggles. Only the solution intended for them touches your lenses.

The case matters as much as the lenses

The case is where biofilm grows, and a contaminated case recontaminates clean lenses every night.

• Empty it completely every morning. Never top up old solution — "topping off" dilutes the disinfectant to the point where it stops working.
• Rub the case with fresh solution, then leave it open and face down to air dry.
• Replace it every three months.

Handling

• Wash and dry your hands before touching a lens, every time. Dry properly — wet hands defeat the point.
• Rub each lens in solution for a few seconds before storing, even with a solution labelled "no rub". The mechanical action removes deposits that soaking alone does not.
• Put lenses in before make-up and take them out before removing it.
• Do not use a lens past its replacement schedule. A monthly lens is not a two-month lens with a bit of care; the material changes and deposits build.

Sleeping in lenses

Unless your lenses are specifically prescribed for overnight wear, do not sleep in them. Closing the eye reduces oxygen reaching the cornea and traps debris behind the lens, and sleeping in lenses raises the risk of microbial keratitis several times over. A nap counts.

Where they come from

Contact lenses are medical devices and require a fitting. The curvature and diameter of your cornea determine which lens fits, and a badly fitting lens can abrade the surface or starve it of oxygen. Coloured and cosmetic lenses are not an exception — they are the same device with pigment, they need the same fitting, and the ones sold from market stalls are a recurring source of corneal damage in Lagos clinics.

Buy from a registered practitioner, and return for the aftercare appointments. They exist to find problems before you can feel them.

When to take them out and see somebody

Immediately, and do not put them back in, if you have:

• Pain that persists after the lens is removed.
• Redness that is getting worse rather than better.
• Marked light sensitivity.
• Blurring that does not clear.
• Discharge, or a white spot visible on the cornea.

The rule of thumb is simple: a problem that goes away when the lens comes out can wait for an ordinary appointment. A problem that does not go away when the lens comes out needs to be seen the same day.

A note on comfort

Lenses that have become uncomfortable after years of trouble-free wear are telling you something — often a change in the tear film, sometimes an allergic response to solution, sometimes a lens material that no longer suits. It is a reason for an appointment, not a reason to persevere or to give up on lenses altogether.