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STARING AT THE MONITOR? Blink often as it helps spread the tears over the ocular surface

Dr. Geetha Iyer, Associate Consultant, Cornea Services, explains, “Imagine the vision you would have if your glasses had scratches. Tears provide a smooth and optically clear surface which enables you to have crystal clear vision. They lubricate the surface to reduce friction as we blink, and provide nourishment to the cornea and ocular surface. The oxygen in the air is dissolved in the tears and is available to the cornea which is without blood supply. Tears also contain various proteins, enzymes, growth and nourishing factors which play an important role in the defence mechanism of the eye.” What is interesting to note is that is the formation of the tear film is an important evolutionary development.

Dr. Scheffer Tseng, M.D. Phd, Director, Ocular Surface Centre and Medical Director, Ocular Surface Research, Miami, USA, an internationally known authority on Ocular Surface Disorders and Dry Eye, who visited Sankara Nethralaya in Chennai recently, says, “When animals moved from water to land, the first thing they developed is the tear film which was meant to protect their eyes in the dry environment of the land. To keep a tear film in a dry environment is such a delicate job. The eye lids have to be in perfect health, tear production has to be optimal and our blink mechanism has to be fine. (As you grow older, the blink mechanism is less swift. If you have diabetes your blink is very bad.) The blink is like the heart beat - it is involuntary.

“The delicate balance seems to be getting upset due to various reasons and “all of a sudden you find that dry eye is very common.” While earlier people used to just brush away symptoms such as burning sensation, redness, increased tearing and tiredness and grit in the eyes after working on computers for prolonged periods or driving for long hours, they are now beginning to wonder whether it could be due to dry eye,” he adds.

Are tears just water? Explains Dr. Bhaskar Srinivasan, Consultant, “Tears are a complex fluid. They have a water component coming from the lachrymal gland in the outer upper portion of the eye, and an oil component from cells in the conjunctiva and glands in the lid.” But how do they get stimulated? “There is a complex interaction between the surface of the eye and the nerve conduction to the brain and the transmission of the impulse from the brain to the glands in order to secrete tears. If this reflex action is upset in any way it may result in dry eye. In addition, the blink action results in the proper spreading of tears over the ocular surface which is why prolonged computer use/television viewing or incomplete closure of the eye can result in dryness. Also the use of contact lenses can aggravate dry eye.”

If lifestyle changes are in some way responsible for dry eye, the ageing population has also contributed to the growing numbers who suffer from the condition. (Dry eye is generally more common among post menopausal women.) Ageing brings with it problems because there is deterioration of tissue.

Adds Dr. S.Vinay, Consultant, “Immunological disorders (patients with diseases like rheumatoid arthritis,) may affect the lachrymal glands, resulting in dryness. Any ocular surgery such as LASIK or refractive surgery can cut the corneal nerves and this reduced sensation can lead to dry eyes. Severe dry eyes could be due to an allergic reaction to certain medication (Steven Johnson’s Syndrome) and can even lead to blindness. Any damage to the lids, causing disturbance in the oil component, can lead to dry eye, due to faster evaporation (most commonly due to seborrhoea or dandruff). And, of course, dry, dusty and sandy environments, and air-conditioning, add to the discomfort of sufferers.

“Dry eye could be a lot worse when you don’t have symptoms, when the eye does not feel what is going on. It could aggravate or complicate the interpretation of an existing eye disease or there could be dry eye in any eye disease. Having a doctor evaluate the problem is important and will help eliminate the stress factors,” says Dr. Tseng.

What then are the relief measures? “If there is any underlying immunological disorder, then it needs to be corrected. Tear supplements and a modification of lifestyle in case of computer professionals are prescribed. In severe cases, the passage which drains the tears to the nose or the throat is blocked permanently or with a plug so that the tears remain in the eye for a longer period and the need for tear supplements decrease. Ensuring lid hygiene also helps.” Incidentally, dry eye has nothing to do with what one eats or drinks or insufficient water intake. Moderate to severe forms of dry eye might require tear supplements life long.

Thankfully in newer tear supplements, the preservative (most of the side effects are because of this) disappears on exposure to sunlight or air, reducing the toxicity of the drops. So the next time you feel like shedding a few tears you will know how precious they are!

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