Understanding Eye Infections
Conjunctivitis is an inflammation of the conjunctiva, the thin, transparent layer that lines the inner eyelid and covers the white part of the eye. The three main types of conjunctivitis are infectious, allergic and chemical. The infectious type, commonly called ‘pink eye’ is caused by a contagious virus or bacteria. Your body's allergies to pollen, cosmetics, animals or fabrics often bring on allergic conjunctivitis. Irritants like air pollution, noxious fumes and chlorine in swimming pools may produce the chemical form.
Common symptoms of conjunctivitis are red watery eyes, inflamed inner eyelids, blurred vision, a scratchy feeling in the eyes and, sometimes, a pus-like or watery discharge. Conjunctivitis can sometimes develop into something that can harm vision so you should see your doctor promptly for diagnosis and treatment. A good way to treat allergic or chemical conjunctivitis is to avoid the cause. If that does not work, prescription or over-the-counter eye drops may relieve discomfort. Infectious conjunctivitis, caused by bacteria, can be treated with antibiotic eye drops. Other forms, caused by viruses, cannot be treated with antibiotics. They must be fought off by your body's immune system.
To control the spread of infectious conjunctivitis, you should keep your hands away from your eyes, thoroughly wash your hands before applying eye medications and do not share towels, washcloths, cosmetics or eye drops with others.
Anything that irritates the eyes can also irritate the eyelids and cause swelling (lid oedema). The most common irritant is an allergy, which can make one or both lids crinkled and swollen. Allergic reactions may be caused by medications instilled into the eyes, such as eye drops, other drugs or cosmetics, or pollen or other particles in the air. Insect stings or bites, as well as infections from bacteria, viruses or fungi, can also cause the eyelids to swell.
Removing the cause of swelling and applying cold compresses may relieve the swelling. If an allergy is the cause, avoiding the allergen can alleviate the swelling; a doctor may also prescribe drug therapy. If a foreign object such as an insect stinger is lodged in the eyelid, it must be removed.
Inflammation of the eyelids (blepharitis) causes redness and thickening, scales and crusts or shallow ulcers often form on the eyelids. Conditions that may occur with eyelid inflammation include staphylococcal infection on the eyelids and in the oil (sebaceous) glands at the edges of the lids, seborrheic dermatitis of the face and scalp and rosacea.
Blepharitis may produce the feeling that something is in the eye. The eyes and lids may itch, burn and become red. The eyelid may swell and some of the lashes may fall out. The eyes may become red, teary and sensitive to bright light. A crust may form and stick tenaciously to the edges of the lid; when the crust is removed, it may leave a bleeding surface. During sleep, dried secretions make the lids sticky. Blepharitis tends to recur and stubbornly resist treatment. It's inconvenient and unattractive but usually not destructive. Occasionally, it can result in a loss of the eyelashes, scarring of the lid margins and even damage to the cornea.
Usually, treatment consists of keeping the eyelids clean, perhaps by washing them with baby shampoo. Occasionally, a doctor may prescribe an antibiotic ointment, such as erythromycin or sulfacetamide or an oral antibiotic such as tetracycline. When the person's skin is also affected with seborrheic dermatitis, the face and scalp must be treated as well.
A stye (hordeolum) is an infection, usually a staphylococcal infection, of one or more of the glands at the edge of the eyelid or under it. An abscess forms and tends to rupture, releasing a small amount of pus. Styes sometimes form simultaneously with or as a result of blepharitis. A person may have one or two styes in a lifetime, but some people develop them repeatedly.
A stye usually begins with redness, tenderness and pain at the edge of the eyelid. Then a small, round, tender, swollen area forms. The eye may water, become sensitive to bright light and feel as though something is in it. Usually, only a small area of the lid is swollen, but sometimes the entire lid swells. Often a tiny, yellowish spot develops at the centre of the swollen area. Although antibiotics are used, they don't seem to help much. The best treatment is to apply hot compresses for 10 minutes several times a day. The warmth helps the stye come to a head, rupture and drain.
When a stye forms in one of the deeper glands of the eyelid, a condition called an internal hordeolum, the pain and other symptoms are usually more severe. Pain, redness and swelling tend to occur in just a very small area, usually at the edge of the eyelid. Because this type of sty rarely ruptures by itself, a doctor may have to open it to drain the pus. Internal styes tend to recur.
A chalazion is an enlargement of a long, thin oil gland in the eyelid that results from an obstruction of the gland opening at the edge of the eyelid.
At first, a chalazion looks and feels like a sty: swollen eyelid, pain and irritation. However, after a few days, the symptoms disappear, leaving a round, painless swelling in the eyelid that grows slowly for the first week. A red or grey area may develop underneath the eyelid.
Most chalazion disappear without treatment after a few months. If hot compresses are applied several times a day, they may disappear sooner. If they remain after 6 weeks, a doctor can drain them or simply inject a corticosteroid.
Extracts in this section compiled from The Merck Manual of Medical Information.