What Is Dry Eye Syndrome? Causes And Symptoms

Dry Eye Syndrome

Dry eye disease or syndrome is a condition of dry eyes, caused by either a decreased level of tear production, or an increased rate of tear film evaporation. In either case, the resulting effect is dry, uncomfortable eyes. Dry eye symptoms usually include pain, light sensitivity, itching, redness, blurred vision, or the feeling of a gritty, foreign object in the eye. The experience of dry eyes can be caused by or aggravated by many factors, such as allergies, or eye strain from using a computer too long.

Keratoconjunctivitis sicca (KCS), commonly referred to as dry eye disease is the most common eye disease in humans, found in almost 6% of all people worldwide. The prevalence rises with age, affecting more than 9% of postmenopausal women, and according to NICE (National for Health Care Excellence) it is reported that 15 to 33% of people aged 65 years or over have this disease.

Types of Dry Eye Disease

Most cases of dry eye disease can be attributed to one of two glands responsible for the excretion of tears not functioning properly. Either the Lacrimal gland, responsible for producing the watery component of tears, or the Meibomian gland, which produces the oily part of tears.
If the lacrimal gland doesn't excrete enough to keep the entire surface of the eye lubricated, tears slowly evaporate and the eye becomes dry. As tears are constantly evaporating, the Meibomian gland helps by excreting a lipid that slows the evaporation process, making our tears last longer. Without this lipid, the rate of evaporation increases, resulting in dry, irritated eyes. 

There are two main types of dry eye; evaporative dry eye and aqueous tear deficient dry eye.

Evaporative Dry Eye

 Also known as Meibomian Gland Dysfunction, or MGD, this may result from blockage or inflammation of the Meibomian glands. These glands are located in the eyelids near your eyelashes.

Aqueous Tear Deficient Dry Eye

 A disorder affected the lacrimal glands. When these glands do not produce enough of the watery component found in tears the result is a dry ocular surface.

What Causes Dry Eye Disease?

There are many possible causes for dry eye syndrome, and not all people affected will have the same triggers, or the same reactions. Some causes may be temporary whilst others may be chronic. Common causes of dry eyes include, but are not limited to:

• Computer Use: When working at a computer or using a smartphone or other portable digital device, we tend to blink our eyes less fully and less frequently, which leads to greater tear evaporation and increased risk of dry eye symptoms. More than 75 percent of women who routinely use a computer at work may suffer from dry eye disease, according to researchers in Japan. Among male workers studied, it was 60.2 percent. Risk factors for dry eye included being over 30 and using a computer for more than eight hours per day.

• Medications: Side effects of over the counter or prescription medication, such as allergy medication, cold medication (specifically nasal decongestants), sedatives or tranquilizers, some blood-pressure medications, and even birth control pills.

• Medical conditions: which relate to the lacrimal or Meibomian glands, the glands responsible for tear production.

• Menopause: Post-menopausal women are at greater risk of dry eyes than men of the same age.

• Aging: Dry eye syndrome can occur at any age, but it becomes increasingly more common later in life, especially after age 50.

• LASIK surgery: after which dry eye symptoms may last up to six months, or longer in rare cases.

• Airborne contaminants: Exposure to dust, smoke, chemical fumes or vapours, or pollen. Dry Eye Syndrome is more prevalent in cities with high levels of air pollution, for example New York or Los Angeles.

• Contact lens wear: Though it can be difficult to determine the exact extent to contact lens wear contributes to dry eye problems, dry eye discomfort is a primary reason why people discontinue contact lens wear.

• Immune disorders: such as diabetes, lupus, rheumatoid arthritis, and Sjögren’s Syndrome - can all contribute to dry eye syndrome.

• Eyelid Problems: Prolonged exposure, where the eyelid may not close completely during sleep - a condition called lagophthalmos, which can be caused by aging or occur after cosmetic blepharoplasty or other causes — can cause severe dry eyes that can lead to a corneal ulcer if left untreated.

• High Altitude: There is 13% more dry eye syndrome at high altitudes.

• Conjunctivitis or infection: of the membrane that lines the inside of the eyelid - although this is inevitably associated with a sticky eye.

• Vitamin levels: either above or below the recommended amounts.

• Indoor Air Environment: Air conditioning, ceiling fans and forced air heating systems all can decrease indoor humidity and/or hasten tear evaporation, causing dry eye symptoms.

• Outdoor environment: Arid climates and dry or windy conditions increase dry eye risks.

• Frequent flying: The air in the cabins of airplanes is extremely dry and can lead to dry eye problems, especially among frequent flyers.

• Smoking: Has been shown to be associated with dry eyes

• Seasonal Allergies: Hay fever may cause an increase in dry eye symptoms

• Hormone therapy treatments: May have an adverse effect on a dry eye condition

• Pregnancy: Pregnancy causes most parts of a woman’s body to change, and the eyes are no exception. Dry eye is a common pregnancy ailment that usually begins toward the end of the first trimester. It will usually continue throughout the pregnancy and possibly for a few months after the baby’s birth.

How Is Dry Eye Disease Treated?

The ability to cure dry eyes syndrome depends entirely on its cause. For environmental causes, such as allergic reactions, reduced exposure to the allergen will result in normal eye comfort in a short period of time. Chronic cases of dry eye disease may require surgical options in order to cure it. Keeping the eyes well hydrated is also key. Both over-the-counter and prescription eye drops are available, and your doctor can help make a recommendation after discussing your symptoms in detail.

Certain causes of dry eye disease may be treatable with prescription eye drops. For irritation caused by lack of tears, mild topical steroids can be helpful. Cyclosporin, an immunosuppressant, can also be used to decrease surface inflammation. While these two methods don't replace or increase tear production, they do help alleviate discomfort associated with dry eye disease.

In some cases, dry eyes may be treatable with medication. For swelling and irritation caused by dry eye disease, a mild topical steroid or topical immunosuppressant may be prescribed. Otherwise, a change in diet and the use of artificial tear drops may provide relief. Foods high in omega-3 fatty acids, such as nuts and fish, may help with increased tear production, as well. In some cases, a cure may not be possible, and regular treatments may be the only option.

Artificial tears are available over the counter, and can help with eye hydration, but will need to be reapplied every few hours.

In the corners of each eye there are small holes, called puncta. These holes are responsible for draining excess tears away from our eyes, through the tear ducts, and into the nasal cavity. Punctal plugs can be inserted into these holes, removing or limiting the ability for tears to drain from the eye. For people suffering from dry eyes, this may allow for tears to accumulate to a comfortable level, eliminating any discomfort. This procedure is usually only recommended for patients that have no had success with prescription medication.

Moisture chamber goggles are available that reduce tear evaporation. By fitting very closely to the face, an almost-air-tight seal prevents the eyes from drying out too quickly. These are especially effective in windy or athletic environments, or even indoor spaces with dry climate controlled air. They can fit easily over the eyes of anyone wearing contact lenses, and for people who already wear corrective eyeglasses, both prescription models and sets designed to fit over your existing frames are available, too.

Do Allergies Cause Dry Eye Syndrome?

Whilst seasonal or environmental allergies can cause dry eyes, this isn't to be confused with dry eye disease. The key differentiating symptom of allergen induced dry eyes is itching. While most other symptoms are the same, including burning, dryness, and irritation, the itchy eye is a main differentiating factor. If you have itchy dry eyes then it is almost certainly an allergen and not dry eye syndrome. 

When allergens are detected by your body's immune system, an abnormal reaction may cause the allergen to be treated like a serious infection. To fight this “infection” antibodies and histamines are produced, which cause inflammation around the eyes and sinuses. Antihistamines are an excellent remedy for most patients, but prolonged use may not be ideal. Seasonal allergies may only require treatments for a few days or weeks, while pet or dietary allergens can remain present until removed from regular exposure.