My grandmother used to tell me to stop crying because it was bad for my eyes. Crying, or to be more precise tears, are not only not bad for the eyes, but serve a vital function in eye health. They provide lubrication and moisture, helping to keep the eyes more comfortable and facilitating vision. When there is an imbalance in the flow or the composition of tears, dry eye syndrome can occur.

What are tears?

The eyes constantly produce tears, not only when we experience emotion. Healthy eyes are covered with a tear film, which prevents the eyes from becoming dry and enables clear vision. The tear film is made up of three layers, oil, water and mucus. The top layer, oil, comes from the melbomian glands which produce fatty oils. The oil lubricates the eyes and slows down the evaporation of tears from the surface of the eyes. The middle layer, produced by the lacrimal or tear glands, consists of water, salt, proteins and antibodies. Their function is to provide moisture to the eyes, cleanse the eyes of irritants, and prevent infection. The inner layer, mucus, enables the tears to spread evenly over the eyes.

What causes dry eyes?

Problems in any of the layers of tear film can lead to dry eyes. Inadequate oil levels can cause the tears to evaporate too quickly, causing dry patches on the surface of the eyes. Any condition that causes blocking of the melbomian glands can cause dry eyes. If the tear glands produce fewer tears or the water layer is too thin, the tear film may become unstable and break down, or cause the oil and mucus layers to touch each other resulting in a discharge from the eyes.

There are a number of factors that can influence adequate production, composition or flow of tears. Although dry eye syndrome can occur at any age, it is more common in older people, particularly post-menopausal women, as part of the natural aging process. Autoimmune conditions such as rheumatoid arthritis, lupus and scleroderma often affect the production of tears, as does diabetes and vitamin A deficiency. Dry eye syndrome can be one of the side effects of certain medications, for example antihistamines, decongestants, diuretics, birth control pills, antidepressants, and some drugs for acne. Sometimes dry eye syndrome is a temporary side effect of refractive eye surgery. Environmental influences include air conditioning or heaters, smoking or a smoky atmosphere, high altitudes or certain climatic conditions. Some contact lens wearers experience dry eyes.

Most people blink about five times a minute. Problems with the eyelids can affect the blinking motion that spreads the tear film evenly across the eyes, causing the eyes to dry out.

Activities that require increased visual concentration, such as extended periods of reading, staring at a computer screen or driving may slow down the blinking rate, leading to dry eyes, but this is temporary.

What are the symptoms of dry eye syndrome?

If you have dry eye syndrome, you may experience a range of symptoms including itching, redness, burning, a gritty feeling in the eyes, blurry vision, extreme sensitivity to light, eye fatigue after reading or watching TV for a short time, discomfort when wearing contact lenses, or mucus in or around the eyes or eyelids particularly on waking up.

Excessive watering of the eyes, which may seem a contradiction to dry eyes, is a typical symptom. This reflex tearing happens because the lack of moisture irritates the eyes, sending a distress signal through the nervous system to the brain for more moisture. A flood of tears is sent to try to make up for the dryness. However, these tears are mostly water, so, although they can wash debris away, they can't coat the surface of the eyes or provide long-term relief.

How are dry eyes treated?

Tests can be performed to reveal the quantity and quality of the tears, as well the tear flow and rate of evaporation of the tears. Generally, the aim of treatment is to keep the eyes lubricated, and there are a number of options to achieve this, depending on the cause and severity of the problem. Discuss these with your optometrist who will guide you to making the most appropriate choice for your condition.

Certain life style changes can help to ease the symptoms of the dry eye condition by making the most of the natural tears. Using a humidifier in the home helps to keep the atmosphere from being too dry. Avoid smoking and smoky places, and wear wrap around glasses outdoors for protection against the drying effects of wind. Be consciously aware of blinking frequently when reading, watching TV or using the computer. There is some evidence that increasing omega-3 and omega-6 fatty acids in the diet may help prevent dry eyes, but this is not conclusive. Sources of these include oily fish, olive oil, walnuts, hemp oil, flax seeds and soybeans.

The most common treatment is artificial tears and ointments. Many types of eye drops are available over the counter to lubricate mildly dry eyes. Your optometrist will be able to recommend suitable products. No one product works for everyone, so you might have to try a few until you find the one that works for you. Eye drops without preservatives are usually preferable, and drops to remove redness often exacerbate the problem so should not be used. If you have chronic dry eye, you need to use the drops even when your eyes feel fine, so that they remain lubricated. The eyes often dry out at night, so it may be best to use an ointment then. A scleral contact lens may be fitted, creating a fluid-filled layer over the eye to prevent it from drying out.

Blocking the tear ducts which drain tears from the eyes may be necessary to conserve tears. This may be temporary, with the insertion of a plug which will dissolve over time, or permanent with a non-dissolving plug or cautery (applying heat to close the tear duct). Either of these may be used in conjunction with artificial tears.

Dry eyes may sometimes result from inadequate closure of the eyelids for a variety of reasons. Some of these may need to be surgically managed.