Conjunctivitis is an inflammation of the conjunctiva, the thin mucous membrane covering the majority of the eye-ball and lining the eyelids. The disease is common amongst children, largely because of their tendency to rub their eyes when they are tired – even though their hands are dirty. This can lead to the virus infection known as pink eye.
There are two types of conjunctivitis, acute and chronic. Acute conjunctivitis can be due to a virus or to bacteria, in which cases it is highly contagious – or to irritant chemicals. It may also be an allergic reaction, as in hay fever. Chronic conjunctivitis is caused by the same things as the acute form of the disorder. It is often found in places associated with air pollution, such as Los Angeles in the USA. Amongst other victims are students and the elderly, whose eyes dry up somewhat through age.
Both forms of conjunctivitis are usually fairly easy to treat, but there is one exception – trachoma. This is a very severe, highly contagious viral conjunctivitis, which is reasonably common in most parts of the underdeveloped world. It is the only form of conjunctivitis likely to lead to blindness.
The nature of the conjunctiva varies according to which parts of the eye it is covering; it lines both the upper and lower lids and the visible part of the eye. The palpebral – eyelid – parts are thick and opaque, with a generous blood supply. At the margins of the lids, these run into the skin; they are also continuous with the linings of the tear ducts and the passages from the eyes to the nose. Over the front of the eye, the conjunctiva consists only of epithelial cells – a thin, see-through covering.
When the conjunctiva is inflamed, the eyes are red and watery, with the redness stretching towards the cornea. There may be a purulent discharge. The lids may be swollen, while the eyes feel as though there is grit under the lids as the watery secretions of the inflamed membrane become thicker. Sometimes the edges of the eyelids may become inflamed and red; this is known as blepharitis.
Diagnosis and treatment
Conjunctivitis is fairly easy to diagnose. In mild cases, the complaint responds to routine home treatment through eye irrigation and eye ointment or drops. If only one eye is infected, it is obviously important to prevent the infection spreading to the other eye. This is best done by observing the rules of simple hygiene and using disposable tissues and towels. If you are using drops, take care not to infect one eye with material from the other. You should avoid touching your face and wiping it with towels used by other people.
Cold compresses and dark glasses are comforting. In acute cases, you will probably be given antibiotic eye drops by your doctor, who will also check that there is no mechanical cause of the infection, such as a trapped eyelash or embedded particle of dirt. Steroid drops are frequently prescribed for allergic conjunctivitis and bring considerable relief. They will probably contain an anti-fungal agent, such as neomycin.
The outlook is good in conjunctivitis, apart from trachoma. If this is suspected, the doctor will refer you to a specialist for expert treatment of the infection.