Dry eye syndrome (DES) is quite a common condition in which you either produce insufficient tears, or the tears that you do produce are of poor quality. This can happen due to a variety of reasons. Unfortunately, it is often very difficult to determine exactly what that reason is.

Understanding Tears

Most people are only aware of their tears when they cry or laugh. However, a tear film, a thin liquid layer, continuously covers your eye and is renewed every time you blink. This tear film helps your eyes to stay moisturized and lubricated, free of dust and clean, and it also helps to prevent infections. The tear film itself contains water, oil, salt, protein and mucus. Different cells and glands inside and around the eye produce it. When any part of this process is disrupted, DES can occur.

Decreased Tear Production

If you do not produce a sufficient amount of tears, you may experience dry eye syndrome. Medically, this is known as keratoconjunctivitis sicca. Some of the most common causes of this include:

• Your age
• Suffering from a medical condition such as a vitamin A deficiency, thyroid disorder, Sjogren’s syndrome, scleroderma, lupus, rheumatoid arthritis, or diabetes
• Taking medications like those for Parkinson’s disease, birth control, acne, high blood pressure, antidepressants, hormones, decongestants, and antihistamines
• Having had LASIK eye surgery, although this usually only leads to temporary DES
• Having damaged the tear glands as a result of radiation or inflammation

Tears Evaporate Too Quickly

There are a number of reasons why your tears may evaporate too quickly. These reasons include:

• You are in an environment with dry air, smoke or wind.
• You don’t blink often enough. This is very common when you concentrate, for instance when working behind a computer, driving or reading.
• You have problems with your eyelids, such as ectropion (where the eyelids turn out) or entropion (where the eyelids turn in).

The Composition of Tears Is Out of Balance

There are three layers to your tears:

1. Water
2. Oil
3. Mucus

Whenever there is a problem with any of these layers, you could develop dry eye syndrome. The Meibomian glands, on the edge of your eyelids, produce a film of oil and these glands often become clogged, for instance. This is particularly common with people who suffer from blepharitis, skin disorders or rosacea.

Risk Factors

There are quite a few things that can disrupt any part of the tear film and tear production. The table below highlights some of these issues and how they affect your eyes.

Medical Conditions

A number of medical conditions can lie at the heart of your dry eye syndrome. This is one of the many reasons why you should always have the problem looked into by a medical professional. Some of the medical conditions include:

• Blepharitis, where the eyelids become inflamed, causing the glands to no longer be able to properly produce tears.
• Rosacea, a condition common in children that makes the skin of the face appear blotchy and red.
• Allergic conjunctivitis, whereby the conjunctiva becomes inflamed. The conjunctiva covers the whites of your eye, as well as the inside part of your eyelids. This is generally caused by an allergic reaction.
• Contact dermatitis, which is a form of eczema that inflames the skin whenever it is in contact with certain substances.
• Sjogren’s syndrome, which is a condition that makes the mouth, eyes and vagina excessively dry. This syndrome is a type of autoimmune disorder, whereby the body’s immune system confuses bodily fluids for foreign invaders, attacking them instead. People with this kind of disorder find that their lacrimal and salivary glands are most affected, which means that the body is no longer able to produce the amount of moisture it needs. Sjogren’s is a chronic disorder and some 4 million people in this country suffer from it. The condition exists in primary form (without any other autoimmune disorder) and in secondary form (whereby the patient also has a different autoimmune disorder). Secondary Sjogren’s is generally more severe and aggressive.
• Rheumatoid arthritis, which makes the joints swell up and become inflamed. Few people realize that it also commonly affects the glands found in and around the eyes.
• Lupus, which is another kind of autoimmune disorder that leads to blood vessels being attacked by the body’s immune system.
• Scleroderma, which leads to parts of the skin, anywhere on the body, to thicken and become hard.
• Bell’s palsy, which is a condition that paralyzes or weakens the muscles on either the right or left side of the face. In some cases, the condition is temporary, although it can also become permanent. Essentially, it is caused by an inflammation of the nerves that control the muscles of the face, leaving them compressed or swollen. Most people find it difficult to close the eye on the side that is affected by this condition, and this means that their eye can become very dry. The condition is most common in those between 16 and 60.
• HIV, a virus that attacks the immune system in the body
• Dehydration, whereby your body simply does not have enough fluid to keep the eyes dry. Dehydration is a medical emergency as it can be fatal. If you suspect this is the case, you must seek immediate medical attention.
• Bone marrow transplants, known as Grafts vs Host Disease or GvHD, which is the reaction of the body to an allogeneic transplant. This means that the host is a different person as the recipient. In some cases, people can have their own bone marrow transplanted, known as autologous bone marrow transplantation. This is usually only done with people who first have their bone marrow removed in order to be able to accept another form of treatment that would destroy the marrow. Because the cells in allogeneic transplants come from a different body, the immune system sees them as foreign and may attack them. In GvHD, it is also possible for the immune cells in the donor bone marrow to attack the host. Usually, this condition doesn’t last long and solves itself.
• Pterygium, which is a growth found on the mucous membrane or conjunctiva of the eye. A pterygium is benign, which means it is non-cancerous. It is usually shaped like a wedge and can extend as far out as the cornea, which includes covers your iris and pupil. Usually, no treatment is required for a pterygium, unless people start to experience vision problems.

The diagram below highlights the process most ophthalmologists will go through in order to determine the cause of someone’s dry eye. A range of tests can be used by ophthalmologists to measure tear quality and quantity.

1. Not enough water or aqueous substances in the eye

1. Dry eye caused by Sjogren’s syndrome

1. Primary
2. Secondary

2. Dry eye not caused by Sjogren’s syndrome

1. Deficiency of the lacrimal gland
2. Obstruction of the lacrimal gland duct
3. Block of the reflexes
4. System drugs and medication

1. Tears evaporate too quickly

1. Intrinsic problems with evaporation

1. Deficiency of Meibomian oil

b.Eyelid disorders

1. Blinking is too infrequent
2. Action of drugs and medication, particularly Accutane

2. Extrinsic problem with evaporation

1. Deficiency of vitamin A
2. Preservatives in topical drugs (including over-usage of eye drops)
3. Wearing contact lenses
4. Allergies or other diseases of the surface of the eye.

Resources and References:

• Facts About Dry Eye – Information on dry eyes. (National Eye Institute)
• Causes of Dry Eye – Causes of dry eyes. (American Academy of Ophthalmology)
• Dry Eye Syndrome – General information on dry eyes. (Healthline)
• NINDS Sjogren’s Syndrome Information Page – Information on Sjogren’s syndrome. (National Institute of Neurological Disorders and Stroke)