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.