Contact Lenses and Acanthamoeba Keratitis

Prof Dr Mervat Salah Mourad, MD

Contact lenses are medical devices and not a makeup tool.

According to my 35 years’ experience in Egypt, if the population understands this phrase, acanthamoeba keratitis can become a historical disease.

Acanthamoeba keratitis became well-known in the 1980’s when the extended-wear contact lenses became popular and people used to sleep with their lenses in, wearing them for very prolonged periods of time without any cleaning. This, among other things, was the cause of the diminishing popularity of those lenses that are now restricted to silicone, high oxygen-permeability lenses, and limited times of wear no more than one month with, at least, weekly cleaning.

Following this, came the second era of acanthamoeba keratitis with the great popularity of the coloured contact lenses. The great increase in incidence with coloured lenses comes from the fact that people use them as a makeup tool without consideration of their need for special care and disinfection. Instead, they are there in the makeup bag with the same chances of disinfection as that taken by eye liner/shadow etc.

In Egypt they can be sold at the beauty salons where the hair dresser can try the colour for the client and, if she does not like it, just put it back in the box without disinfection, waiting for the next client. I also noticed in my patients, high school girls were each buying one colour and then exchanging them together according to the colour of the dress they wear.

Acanthamoeba keratitis is caused by protozoa that have a vegetative form (trophozoite) when the conditions are favourable, but when the surrounding conditions get unfavourable, such as when they face our medical treatment, they turn into cyst form and can stay as a cyst for years, very resistant to treatment.

Why do we have this link between the contact lenses and the acanthamoeba keratitis? We have this because acanthamoeba cannot penetrate an intact corneal epithelium but only need a minute abrasion in the corneal epithelium, which is offered by the lens if the patient rubs their eyes with the lens on, or if the lens has deposits on its inner surface. As we know, the lens has a great amount of water in its structure so if it is not well disinfected, acanthamoeba can invade the cornea through the minute abrasion and cause keratitis.

This keratitis is very resistant to treatment due to the encysting process, and is very liable to recurrence after initial improvement and subsequent cessation of treatment, after which the cysts turn into trophozoites and activate keratitis once more. Accordingly, treatment must be continued some time (months) after clinical improvement, but above all, prophylaxis is the best way to save eyes.

This keratitis is characterised by severe pain that is out of proportion to the keratitis present due to damage of the corneal nerves (neuro-keratitis). This gives rise to irregular epithelium with linear or dendritic stromal infiltrations, which eventually reach ring pattern infiltration.

Finally, if ever an ounce of prevention is worth a pound of cure it is true here in this devastating resistant recalcitrant disease that leads to blindness.

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