A stye (also spelled "sty") develops when a gland at the edge of the eyelid becomes infected. Resembling a pimple on the eyelid, a stye can grow on the inside or outside of the lid. Styes are not harmful to vision, and they can occur at any age.

A stye initially brings pain, redness, tenderness and swelling in the area, then a small pimple appears. Sometimes just the immediate area is swollen; other times the entire eyelid swells. You may notice frequent watering in the affected eye, a feeling like something is in the eye or increased light sensitivity.

Styes are caused by staphylococcal bacteria. This bacterium is often found in the nose, and it's easily transferred to the eye by rubbing first your nose, then your eye.

Most styes heal within a few days on their own. You can encourage this process by applying hot compresses for 10 to 15 minutes, three or four times a day over the course of several days. This will relieve the pain and bring the stye to a head, much like a pimple. The stye ruptures and drains, then heals.

Never "pop" a stye like a pimple; allow it to rupture on its own. If you have frequent styes, your eye doctor may prescribe an antibiotic ointment to prevent a recurrence.

Styes formed inside the eyelid either disappear completely or (rarely) rupture on their own, and they can be more serious. These styes may need to be opened and drained by your eyecare practitioner

The conjunctiva is the thin, clear membrane over the white part of the eye; it also lines the eyelids. Inflammation of this membrane is called pink eye or conjunctivitis

The most obvious symptom of pink eye is, of course, a pink eye. The pink or red color is due to inflammation. Your eye may also hurt or itch.

How can you tell what type of pink eye you have? The way your eyes feel will give some clues: Viral conjunctivitis usually affects only one eye and causes excessive eye watering and a light discharge. Bacterial conjunctivitis affects both eyes and causes a heavy discharge, sometimes greenish. Allergic conjunctivitis affects both eyes and causes itching and redness in the eyes and sometimes the nose, as well as excessive tearing. Giant papillary conjunctivitis (GPC) usually affects both eyes and causes contact lens intolerance, itching, a heavy discharge, tearing and red bumps on the underside of the eyelids. To pinpoint the cause and then choose an appropriate treatment, your doctor will ask some questions, examine your eyes, and possibly collect a sample on a swab to send out for analysis. Give a careful account of the episode, because oftentimes your answers alone with reveal the diagnosis.

Tears bathe the eye, washing out dust and debris and keeping the eye moist. They also contain enzymes that neutralize the microorganisms that colonize the eye. Tears are essential for good eye health. In dry eye syndrome, the eye doesn't produce enough tears, or the tears have a chemical composition that causes them to evaporate too quickly. Eyes are lubricated from three different glands around the eyes. See animation. Punctal plugs are often very effective in relieving dry eyes. See animation. Dry eye syndrome has several causes. It occurs as a part of the natural aging process, especially during menopause; as a side effect of many medications, such as antihistamines, antidepressants, certain blood pressure medicines, Parkinson's medications, and birth control pills; or because you live in a dry, dusty or windy climate. If your home or office has air conditioning or a dry heating system, that too can dry out your eyes. Another cause is insufficient blinking, such as when you're staring at a computer screen all day. Dry eyes are also a symptom of systemic diseases such as lupus, rheumatoid arthritis, rosacea or Sjogren's syndrome (a triad of dry eyes, dry mouth, and rheumatoid arthritis or lupus). Long-term contact lens wear is another cause; in fact, dry eyes are the most common complaint among contact lens wearers. Recent research indicates that contact lens wear and dry eyes can be a vicious cycle. Dry eye syndrome makes contact lenses feel uncomfortable, and the rubbing of the lenses against the conjunctiva seems to be a cause of dry eyes. Incomplete closure of the eyelids, eyelid disease and a deficiency of the tear-producing glands are other causes. Tears are composed of three layers: the outer, oily, lipid layer; the middle, watery, lacrimal layer; and the inner, mucous or mucin layer. Each layer is produced by a different part of the eye (the lacrimal gland produces the lacrimal layer, for example), so a problem with any of those sources can result in dry eyes. Dry eye syndrome is more common in women, possibly due to hormone fluctuations. Recent research suggests that smoking and taking multivitamins can increase your risk of dry eye syndrome, and that eating a lot of omega-3 fatty acids (found in cold-water fish) may decrease your risk.

Conjunctivitis may be triggered by a virus, bacteria, an allergic reaction (to dust, pollen, smoke, fumes or chemicals) or, in the case of giant papillary conjunctivitis, a foreign body on the eye, typically a contact lens. Bacterial and viral systemic infections also may induce conjunctivitis.

Dry eye syndrome is a chronic lack of sufficient lubrication and moisture in the eye. Its consequences range from subtle but constant irritation to ocular inflammation of the anterior (front) tissues of the eye.

Persistent dryness, scratching and burning in your eyes are signs of dry eye syndrome. These symptoms alone may be enough for your eye doctor to diagnose dry eye syndrome. Sometimes he or she may want to measure the amount of tears in your eyes. A thin strip of filter paper placed at the edge of the eye, called a Schirmer test, is one way of measuring this.

Some people also experience a "foreign body sensation," the feeling like there's something in the eye. And, it may seem odd, but sometimes watery eyes can result from dry eye syndrome, because the excessive dryness works to overstimulate the watery component of your eye's tears.

Avoidance. Your first line of defense is to avoid the cause of conjunctivitis. Both viral and bacterial conjunctivitis spread easily to others. Here are some tips to avoid spreading the conditions or re-infecting yourself:

1. Wash your hands frequently, and avoid touching or rubbing your eyes.
2. Don't share washcloths, towels or pillowcases with anyone else, and wash these items after each use.
3. Don't share eyedrops or cosmetics such as eyeliner, eye shadow or mascara. Replace them after you're healed, to avoid re-infection.
4. Your eyecare practitioner may recommend that you discontinue contact lens wear during this time or replace your contact lenses after you're healed.
5. Warm compresses may help soothe your eyes if you have viral or bacterial conjunctivitis.

To avoid allergic conjunctivitis, keep windows and doors closed on days when the pollen is heavy. Dust and vacuum frequently to alleviate potential allergens in the home. Stay in well-ventilated areas if you're exposed to smoke, chemicals or fumes. Cold compresses can be very soothing. If you've developed giant papillary conjunctivitis, odds are you're a contact lens wearer. You'll need to stop wearing your contact lenses, at least for a little while. Your eye doctor may also recommend that you switch to a different type of contact lens, to prevent the conjunctivitis from recurring. For example, you might need to go from soft contacts to gas permeable ones, or vice versa, or you might need to switch to a type of lens that you replace more frequently, such as from conventional contact lenses to daily disposable ones. GPC can also result from prosthetics, stitches and more. Your eye doctor will decide if removal is appropriate. Medication. Doctors don't normally prescribe medication for viral conjunctivitis because it usually clears up on its own within a few days. Antibiotic eyedrops will alleviate bacterial conjunctivitis, whereas antihistamine allergy pills or eyedrops will help control allergic conjunctivitis symptoms. For giant papillary conjunctivitis, your doctor may prescribe eyedrops to reduce inflammation and itching. Usually, conjunctivitis is a minor eye infection, but sometimes it can develop into a more serious condition. See your eye doctor for a diagnosis before using any eyedrops in your medicine cabinet from previous infections or eye problems.

Dry eye syndrome is an ongoing condition that may not be cured (depends on the cause), but the accompanying dryness, scratching and burning can be managed. Your eyecare practitioner may prescribe artificial tears, which are lubricating eyedrops that may alleviate the dry, scratching feeling. Restasis eyedrops (cyclosporine in a castor oil base) go one step further: they help your eyes to increase tear production. Restasis treatment is the first of its kind. If the problem is environmental, you should always wear sunglasses when outdoors, to reduce exposure to sun, wind, and dust. Indoors, an air cleaner can filter out dust and other particles from the air, while a humidifier adds moisture to air that's too dry because of air conditioning or heating. Temporary or permanent silicone plugs in the lacrimal (tear) ducts keep tears in your eye from draining away as quickly. Called lacrimal plugs or punctal plugs, they can be inserted painlessly while you're in the eye doctor's office and are normally not felt once inserted. A new type of punctal plug made of acrylic is a small rod that becomes a soft gel when exposed to your body heat after insertion. It is designed to accommodate to the size of any punctum canal. Advantages of this type of plug are that one size fits all so measurement is unnecessary, and nothing protrudes from the tear duct that could potentially cause irritation. Sometimes, however, the tear ducts need to be closed surgically. Doctors sometimes recommend special nutritional supplements for dry eyes. Studies have found that supplements containing certain essential fatty acids (linoleic and gamma-linolenic) can decrease dry eye symptoms. If medications are the cause of dry eyes, discontinuing the drug generally resolves the problem. But in this case, the benefits of the drug must be weighed against the side effect of dry eyes. Sometimes switching to a different type of medication alleviates the dry eye symptoms while keeping the needed treatment. In any case, never switch or discontinue your medications without consulting with your doctor first! Treating any underlying eyelid disease, such as blepharitis, helps as well. This may call for antibiotic or steroid drops plus frequent eyelid scrubs with an antibacterial shampoo. Quite a few products are in testing for possible dry eye treatment. For example, trehalose (a carbohydrate) improved dry eye symptoms in small studies, but further testing is needed. If contact lens wear is the cause of your dry eyes, your eyecare practitioner may want to switch you to a different lens or have you wear your lenses for fewer hours each day. In a few cases, it is recommended that contact lens wear be discontinued altogether until the dry eye problem is cleared up. If you are considering LASIK, be aware that dry eyes may disqualify you for the surgery, at least until the problem is resolved. Dry eyes increase your risk for poor healing after LASIK, so most surgeons will want to treat the dry eyes first, to ensure a good LASIK outcome. This goes for other types of vision correction surgery, as well.