A guide to common eye infections © Thinkstock
Conjunctivitis is a harmless infection that affects the conjunctiva, a transparent membrane that covers the inside of the eyelids and lines part of the ocular globe. It’s generally caused by a virus (adenovirus) or by bacteria (staphylococcus, streptococcus, pneumococcus or haemophilus). The infection can also be caused by allergies.Conjunctivitis is normally diagnosed when:The eye becomes red and feels itchy.Thin or thick secretions cover the eye, making it difficult to open in the morning.Conjunctivitis, especially when it’s caused by a virus, is mostly harmless and will usually clear up within a few days. At the same time, the infection tends to spread to the other eye, so it’s a good idea to use different drops for each eye. It’s highly contagious, so you have to be careful. Avoid rubbing the infected eye, wash your hands regularly and don’t leave compresses lying around before you wash them to stop the infection spreading to other people. For the same reasons, don’t use eye drops that have expired, as the bottle could contain germs that lead to conjunctivitis. Some forms of conjunctivitis can be more serious: in newborn babies who have caught the infection during birth from gonococcus, chlamydia or type 2 herpes in the mother. Conjunctivitis caused by chlamydia trachomatis leads to the development of a trachoma and is the most common cause of blindness in the world. Bad hygiene often plays a role in the development of conjunctivitis. It can be prevented simply through washing your hands and will disappear quickly when treated with antibiotics.These bacterial infections are also quite common. Small red swellings develop around the roots (or follicles) of the eyelashes around the edge of the eye. These are mostly caused by staphylococcus, as is the case with boils, and a few sties can develop around the eye. After the sty has burst, it will heal by itself. All you have to do is apply an antiseptic cream or a warm, damp dressing to help the process.Chalazions, similar to sties, are an inflammatory reaction caused by the obstruction of tiny glands called Meibomius, which produce the oily substance in tears. Unlike sties, chalazions are painless, but they can make the eye vulnerable to further infection.Other tissues in the eye can also become infected. The cornea, a transparent fibrous membrane covering the eye, is particularly susceptible. Keratitis can either be a viral infection (caused by the adenovirus, herpes or varicella zoster viruses), a bacterial infection of a fungal infection. Contact lens wearers are particularly at risk.Corneal infections can lead to the appearance of erosions and ulceration on the cornea, which alter your vision and can become troublesome. Keratitis usually only affects one eye, making it red, painful and sensitive to light.If you get keratitis, you should consult an eye specialist. Eye drops with antibacterial or antiviral properties may be prescribed in some cases to fight the infection and prevent the cornea from turning opaque and obscuring your vision in the long term. The symptoms will take longer to clear up than conjunctivitis.Herpetic keratitis is treated with aciclovir, an antiviral prescription drug that’s taken orally or given intravenously. You can’t use this with creams containing corticoids, as these could worsen the infection. One of the key problems with this form of keratitis is that it tends to come back, so a long course of treatment with aciclovir may be required to get rid of it.Ophthalmic zoster is a secondary infection of the ophthalmic part of the trigeminal nerve, caused by the varicella zoster virus. It manifests itself through inflammation of the cornea, causing intense pain. It can also affect the uvea, retina and motor nerves in the eye, and can lead to paralysis of the eye in such cases. The uvea, which is made up of the iris, ciliary body (which produces the aqueous humour) and a vascular membrane called the choroid, can also be prone to infection. Certain viruses like the cytomegolovirus, and parasites like toxoplasma, can also cause infections of the retina, especially in people with low immunity or people suffering from AIDS.
Dr Corinne Tutin
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