A parasite from my contact lens is gnawing into my eyeball: The gruesome truth about a scarily common bug
By Keith Poole
My face frozen in a contorted grimace, I could still make out the blunt steel needle closing in on my eye.
‘Keep still, and open your eye as wide as you can,’ said the doctor, as she scraped a sample of tissue from my cornea. Even with an anaesthetic drop in my eye, I could feel a sharp pain as, for several excruciating seconds, the metal rubbed against one of the most delicate areas of the body.
I had to fight all my instincts to keep my head perfectly still. The doctor, nervous herself, drew back with what looked like a small piece of curled cellophane. I took my head out of the chin support and breathed for the first time in what seemed a very long period.
But the respite was short-lived. Five more tissue samples to go. Five! By the third, I was on the verge of telling her it would be easier just to take the eyeball out.
I could hardly take on board what was happening. Four weeks earlier I’d gone to my pharmacist for ointment to help with an itch I’d put down to a minor infection. Now I found myself in hospital, my right eye infected with a parasite called acanthamoeba.
Anyone who wears contact lenses will have heard about this – it’s the bug opticians warn you about when you have an eye test.
Acanthamoeba infection is what you are told you risk by not keeping your contacts clean. I took the warning on board – but found out later that keeping lenses clean isn’t a full-proof defence.
In fact, this ‘bug’ is not a bacteria or a virus, but an amoeba – the most basic sort of animal. So I have an animal living in my eye. In fact, there are hundreds swimming about. And yes, they have tails, too.
These animals are tiny; 15 microns long. (To give you an idea, 500 microns is half a millimetre.) They love the cornea, as food is plentiful. They eat the protein in your eye and they eat any bacteria that gets in.
There is nothing the human body can do to repel them. There is no immune system in the cornea, as it is not supplied by blood vessels. Left to munch and burrow deeper, the amoeba eventually perforate the eyeball itself, causing total vision loss.
If you develop an acanthamoeba infection, the only solution is what doctors call ‘aggressive ‘ treatment.
The excruciating scraping of my eye? It seems that wasn’t the treatment at all – it was just to provide samples to confirm I had the infection.
The war with my acanthamoeba invader had only just been declared. For the treatment itself I had to be admitted for an overnight stay in Queen Victoria Hospital in East Grinstead, East Sussex, one of the few NHS corneal specialist units in the country.
The only attack against this simple organism is frighteningly primitive: a barrage of chemical eyedrops – all slightly different versions of antiseptics.
One is the chemical that surgeons use to wash their hands before theatre… and it stings. Every hour, night and day, three different types of these drops were put into my eye, spaced at five minutes apart.
Under this onslaught, the white of my eye quickly turned painfully raw. I’d been pumped full of all sorts of painkillers, but the stinging from every barrage was searing and I could not sit still, let alone sleep.
Twenty-four hours later I was told I’d responded well to the treatment. But any hopes I had of it being over were dashed by my consultant ophthalmologist, Damian Lake.
‘Treatment lasts for many, many, months, if not years,’ he told me. ‘I would say the minimum is three months, and the average is 12 months.
‘The treatments we have are not good. We know of nothing that will just kill it; it’s very hard to shift. It can be a long war of attrition.’
More like a siege. Acanthamoeba has an almost invincible defence mechanism. As soon as it detects a threat, it puts up a chemical barrier, like a concrete wall, and goes into hibernation. In this state, it can survive for months on very little food, hoping for the coast to clear, when it will pop out its tail again and continue on its sinister way.
Although the drops kill off some of the amoeba, the long-term hope is to starve them, or for the chemicals finally to seep through the amoeba’s protective barrier.
Putting the drops in is a dispiriting and painful affair. Even after I was discharged from hospital, I still had to administer them every two hours, and then, after a week, every four.
A few days later, the parasites fought back – and I am now back on the drops every two hours.
‘It is quite normal for the infection to flare and subside,’ Mr Lake tells me. ‘We have to be constantly vigilant – with an appointment every week.
HOW TO AVOID THE SAME FATE
John Dart, ophthalmologist and deputy director of research at Moorfields Eye
Hospital, says infection with acanthamoeba can largely be avoided by sticking to simple hygiene measures.
- Keep your contact lens case clean and renew it monthly.
- Stick to the daily disinfection routine recommended by your optometrist; or use daily disposable soft lenses.
- Don’t use non-sterile water on your lenses.
- Never swim in contact lenses.
- Avoid getting tap water in your eyes when wearing lenses (such as when washing your face or showering).
If you develop chronic eye irritation and inflammation (over a few days) which affects your vision, you should see an
ophthalmologist and check that acanthamoeba has been excluded. Most patients respond well when the specialised treatment is given early.
‘After three months, we hope to go down to drops four times a day. But there will come a time when we have to stop them and just wait to see if the parasites come back.’
In some cases, patients need a corneal transplant. But this is a last resort, as there is no way of replacing the whole cornea with a graft, so there is a risk that you do not cut out all of the infection – and so the saga goes on.
Meanwhile, looking through my right eye is like peering through a fogged windscreen. At one point, I could not read a number plate from a yard away. My eyesight has improved dramatically since the start of my treatment, but is nowhere near where it was.
As it was caught early (within six weeks), the doctors are hopeful I’ll make a full recovery. The symptoms – redness, irritation, mild sight loss and swelling – mean diagnosis is tricky, as acanthamoeba can be confused with so many other infections.
Although the infection is rare, numbers have risen with the use of contact lenses.
‘It is a horror story for us,’ admits Mr Lake, explaining that acanthamoeba was first discovered in the 1970s.
‘I blame Napoleon,’ he adds. ‘Acanthamoeba loves standing water, and because we were terrified Napoleon would poison the water 200 years ago, we all started designing houses with water tanks in our roofs.’
While people can catch it from swimming in stagnant ponds or lakes, contact lens wearers are particularly at risk. The important thing is to avoid water.
Mr Lake believes you’re at risk even just keeping your contact lens case in the bathroom, as it can be splashed by water.
The safest form of lens is the daily disposable, as any acanthamoeba will end up in your bathroom bin.
I wish that the optician had warned me of all this before I changed from daily disposables to fornightlies. From now on, I’m sticking to the specs.