Contact Lens Eye Infections, From a Painful Red Eye to a Corneal Ulcer

Contact lenses give many people freedom from glasses. They also sit directly on the cornea, the clear window at the front of the eye. When they are cleaned, stored or worn badly, they can carry germs onto it. The result can be a painful red eye and, in the worst cases, an ulcer on the cornea that threatens sight. This guide explains contact lens eye infections, using the patient information of Moorfields Eye Hospital in London. It covers the warning signs, how treatment works, a rarer and more serious infection called acanthamoeba keratitis, and the habits that lower the risk.

What microbial keratitis is

Moorfields describes microbial keratitis as an infection on the cornea. It is often related to contact lens wear. Less commonly, it follows a scratch on the surface of the eye or an existing eye condition.

The word keratitis means inflammation of the cornea, and microbial means it is caused by a microbe. It can be a serious condition if it is not treated, and it can sometimes affect vision and leave a scar, even with the correct treatment. A guide on corneal blindness and cornea transplant explains what scarring of the cornea can lead to.

The warning signs

Moorfields lists the symptoms.

• A painful red eye.
• Blurred vision, for some people.
• The feeling of something in the eye.
• Pain that grows as an ulcer develops on the surface of the cornea.
• A small white spot on the cornea, over the coloured part of the eye, which can sometimes be seen.

The advice on when to seek help describes the same picture. It is an eye that is getting more red and painful rather than better, with a white spot on the cornea that is getting bigger.

What raises the risk

Infection is more likely with incorrect contact lens cleaning or storage, with incorrect use of disposable lenses, and with wearing lenses overnight. These are habits that a lens wearer can change.

Anyone who wears lenses should also know the fitting check. After an infection has fully recovered, Moorfields says to return to the contact lens practitioner to check the fit and use of the lenses.

How doctors find the cause

In some cases, after local anaesthetic drops have numbed the eye, the doctor takes a sample from the corneal ulcer. The sample shows which bacteria are causing the infection, so that treatment can be planned. Results can sometimes take several days to come back, depending on the bacteria being tested for.

How it is treated

Antibiotic drops are usually used. At first the drops may need to go in very often. Moorfields says this can be up to every hour, and sometimes through the night if the infection is severe. The frequency is reduced once the ulcer is seen to be getting smaller. Sometimes the antibiotic is changed if there is no sign of improvement after several days, or if the sample results show that another drop would suit better.

Moorfields stresses one point above all. It is very important to put the drops in regularly, because these infections can get much worse if they are not treated properly.

Contact lenses must stay out. Do not wear them while the infection is present. Do not wear them for a few weeks after it clears either. Wearing them too soon can lead to a serious deterioration in the condition.

Putting in the drops properly

With drops needed so often, technique matters. Moorfields gives these steps in a video on its page, and a separate guide covers putting in eye drops safely in more detail.

• Check that the drops are still in date, and that the seal of a new bottle is not broken.
• Make sure the correct drops are going into the correct eye.
• Wash your hands thoroughly with soap and water, and mix the contents of the bottle by turning it over two or three times.
• Tilt your head back and pull down the lower lid to form a small pocket.
• Keep the tip of the bottle from touching the skin or eyelashes, as this could contaminate the drops.
• Look up and squeeze gently so that a single drop falls into the pocket.
• Blink, and press lightly on the inner corner of the eye so more of the drop is absorbed and less runs down the tear duct.
• Wipe away any excess with a clean tissue, and wait at least five minutes before putting in another drop.
• Wash your hands again to remove any trace of the medicine.

Follow-up and when to seek advice

In some cases the person is asked to return in a few days to see whether the infection is improving. If the infection is mild, the person may be asked to return only if the symptoms get worse.

The warning signs of a failing treatment are clear. Moorfields says to seek advice, or go to a local emergency department, in these situations.

• The eyesight becomes more blurred.
• The eye becomes more red or painful rather than improving.
• A white spot on the cornea gets bigger.

A rarer infection, acanthamoeba keratitis

Moorfields describes a second corneal infection that can be very painful. Acanthamoeba keratitis, or AK, is caused by a microscopic organism called acanthamoeba. It is common in nature. It is usually found in bodies of water such as lakes, oceans and rivers. It is also found in domestic tap water, swimming pools, hot tubs, soil and air. Acanthamoeba does not generally harm people, but it can cause a serious eye disease if it infects the cornea. It is a rare condition.

AK is most common in people who wear contact lenses, although anyone with a corneal injury is susceptible. Around 85% of cases have been associated with contact lens wear. The biggest risk factor is exposure to water. Moorfields names swimming or showering in contact lenses, rinsing or storing lenses in water, and handling lenses with unwashed or wet hands. Poor hygiene, such as not disinfecting lenses properly and not cleaning and changing lens cases regularly, also increases the risk.

In the early stages the cornea can become irregular because of infection and inflammation, which can affect vision, and there may be light sensitivity and watering. AK can be extremely painful, though not all patients have intense pain. Vision can get worse quite suddenly in the early stages, and the person should tell the eye doctor as soon as possible if that happens. In the later stages, scarring from long-term inflammation is usually the reason for sight loss.

The outcome can be serious. Moorfields says that a degree of permanent vision loss occurs in around a quarter of cases. Around 25% of the cases it sees result in a corneal transplant. Moorfields also notes that it is extremely unlikely for acanthamoeba to spread from person to person.

Why an infected cornea hurts so much

In its information on acanthamoeba keratitis, Moorfields explains why corneal infections hurt as they do. The cornea is one of the most sensitive tissues in the body, and it has the highest density of pain receptors in the body. This means that any injury to the cornea can be very painful. Pain can also be triggered by the immune response to the infection, an inflammatory response that may be one reason the eye is red as well as painful.

The medicines can add to the discomfort. The drugs used to treat acanthamoeba keratitis can be quite harsh. In some cases they irritate the surface of the cornea. The doctor therefore tries to strike a balance between treating the infection and preventing further irritation.

Light sensitivity has its own reason. The cornea is usually clear, but when it is infected it turns cloudy and scatters light around the eye. A drop that temporarily widens the pupil can add to the light sensitivity, even though it may help to relieve pain. Tears are a natural reflex to the disruption of the corneal surface, and their job is to remove irritants from the surface of the eye.

Moorfields also suggests sensible precautions with drops. Wash your hands and dry them thoroughly before and after putting in drops, and take care not to touch the eye with the dropper or the bottle top.

Habits that lower the risk

Drawing on the risk factors the hospital names, the following habits make sense for anyone who wears lenses.

• Keep lenses away from water. Do not swim or shower in them, and do not rinse or store them in water.
• Wash and dry your hands before touching lenses.
• Disinfect lenses properly, and clean and change the lens case regularly.
• Use disposable lenses as they are meant to be used.
• Do not wear lenses overnight.
• Return to your lens practitioner to check the fit and the way you use your lenses.

A guide on who should be tested for blurred vision explains how glasses and lenses are prescribed in the first place.

Questions to ask your eye doctor

• Which germ is causing my infection, and has a sample been taken?
• How often should the drops go in, and for how long?
• When should I be seen again, and which signs mean I should return sooner?
• When can I wear lenses again, and should my lens fit be checked first?
• Is there a risk of a scar on the cornea?

If an eye with a lens turns red

Take the lens out, do not put it back in, and have the eye examined. For general questions after arranging an examination, ask PEBS about contact-lens eye infections. To make a gift, review the hospital’s donation methods.

Careful cleaning and storage protect the cornea, and an eye that is red and sore with a lens in it should be seen without delay.

This article is general information and does not replace an examination by an eye doctor.