What is dry eye syndrome?
Dry eye syndrome (keratoconjunctivitis sicca) is a chronic reduction in the quantity or quality of tears, causing insufficient lubrication of the eye. It can cause mild to severe discomfort and damage to the tissues of the surface of the eye - the cornea and conjunctiva.
What are the symptoms of dry eye syndrome?
Symptoms of dry eye syndrome include:
- Eye irritation and redness
- A gritty or burning sensation to the eyes
- A foreign body sensation - the feeling that something is in your eye
- Filmy vision (that may clear with repeated blinking)
- Sensitivity to light
- Contact lens discomfort or intolerance
What causes dry eye syndrome?
The normal tear film of the eye has three components:
Most of our tear film is composed of a watery substance, secreted by the lacrimal glands which are located above and behind our upper eyelids. This watery (or aqueous) component of our tears nourishes and cleans the cornea and other tissues on the front of the eye.
Oils secreted from Meibomian glands (located at the margins of our eyelids) help keep our tears from evaporating too quickly.
Mucin is a mucous-like substance that is produced by cells in the conjunctiva and outer surface of the eye. It helps tears spread more easily across the cornea.
A deficiency in the quantity or quality of any of these three components of the tear film can cause dry eye syndrome.
A deficiency in the watery component of tears is known as Aqueous Tear Deficiency (ATD). Keratoconjunctivitis sicca (KCS) is the medical term used to describe dry eye syndrome resulting from ATD. A more common form of dry eye is Evaporative Dry Eye which is related to meibomian gland dysfunction and blepharitis.
Who is at risk of dry eye syndrome?
Risk factors for dry eye syndrome include:
- Age. Our tear glands produce fewer tears as we get older. Many people begin to notice dry eye symptoms after age 40.
- Gender. Women are more likely to have dry eyes than men due to hormonal changes that accompany menstruation, pregnancy, and menopause.
- Contact lens wear. Soft contact lenses in particular can cause tears to evaporate more quickly.
- Computer use. We blink our eyes less frequently when using a computer. This increases tear evaporation.
- Dehydration. Failure to drink enough fluids can lead to general dehydration and dry eye symptoms.
- Alcohol and caffeine consumption. Both can lead to dehydration and dry eyes.
- Environmental conditions. Exposure to smoke, wind, air pollution, air conditioning, and dry climates can cause eye irritation and dryness. The partially-recirculated air in airplane cabins is especially dry and irritating.
- Medications. Many medications, including antihistamines, decongestants, oral contraceptives, blood pressure and ulcer medications, and antidepressants can cause dry eye symptoms.
- Health conditions. Health problems that affect the body's ability to produce tears include arthritis, diabetes, thyroid disease, asthma, and lupus.
- Sleeping with eyes partially open. Some people sleep with their eyes partially open, with the exposure causing the eyes to dry overnight.
How common is dry eye syndrome?
Dry eye is a very common disorder that affects a significant percentage of the population - especially people over age 40. Studies vary in their estimations of this percentage, but at least one survey suggests that approximately 20 percent of people suffer from dry eye syndrome. Some researchers believe 75 percent of the population over age 65 experiences dry eye symptoms.
How is dry eye syndrome diagnosed?
If you suspect you have dry eyes, you should make an appointment to see your optometrist. He or she will ask you a number of questions about your symptoms and health history and perform one or more diagnostic tests to determine if you have dry eye syndrome.
One common diagnostic test for aqueous deficiency dry eye is called the Schirmer test. It is performed by placing a standardised strip of filter paper under your lower eyelid. An anesthetic eye drop is sometimes instilled prior to positioning the paper strip. You will then be asked to keep your eyes closed for five minutes. The extent of wetting of the strip is then measured to determine how effectively your lacrimal glands are producing the aqueous component of your tears.
Another common diagnostic test for evaporative dry eye is called the Tear Break-Up Test (TBUT). It is performed by placing a small amount of a fluorescent dye in your tear film. Your optometrist will then examine your eyes with a blue light. The dye mixes with your tears and causes the tear film on your eyes to glow under the examination light. You will be asked to blink several times and then keep your eyes open as long as you can without blinking. Your optometrist will measure how long it takes for dark spots to appear on your cornea, indicating that the tear film has broken up and the surface of your eye has become dry at those spots. A tear break-up time of less than 10 seconds suggests an unstable tear film and evaporative dry eye.
Your optometrist may perform other tests in place of (or in addition to) the Schirmer test and/or Tear Break-Up Time test to determine whether or not you have dry eye syndrome.
How is dry eye syndrome treated?
There are a number of ways to treat dry eyes. The treatment we will choose for you will depend on the type and severity of your condition.
Mild cases of dry eye syndrome can be treated with non-prescription artificial tears. There are many brands and formulations to choose from, including preservative-free products in single-dose packaging for people with sensitive eyes. Your optometrist will prescribe one or more types for you to instil. Preservative free artificial tear single dose capsules include Refresh, Bion Tears and TheraTears. Alternatively Hylofresh is a preservative free drop in a bottle.
Lubricating Ointments and Gels
In some cases, your optometrist will recommend that you supplement daytime use of artificial tears with bedtime use of a lubricating ointment or gel. If so, you will be instructed to put about a half-inch application of the ointment inside your lower lid. Your body heat will melt the ointment and your lids will spread it across your eye when you blink. Ointments stay on your eyes much longer than artificial tears, but they will blur your vision. For this reason, ointments are generally only applied at bedtime. For more severe dry eye a night-time ointment such as Vita-A Pos is preferable, for moderate dry eye an effective lubricant is Genteal Gel or ViscoTears.
Manuka Optimel drops drops are based on honey and have been found to reduce ocular bacterial flora and reduce surface inflammation. They have the unfortunate side effect of a transient stinging upon insertion. More information can be found here.
For more significant dry eye problems related to lacrimal gland dysfunction, we may recommend a procedure called punctal occlusion. This procedure reduces your tear outflow by blocking the ducts in your lids that drain tears away from your eyes. Punctal occlusion involves inserting small plugs in the openings (puncta) of the tear drainage ducts that are located on the inner surface of each eyelid, near the nose. The punctal plugs may be temporary (made of collagen that dissolves in a week or two) or permanent (made of silicone). If necessary the permanent plugs can be removed later. The procedure is painless and takes only a few minutes. Punctal occlusion may eliminate or significantly reduce your need for artificial tears. Ask your optometrist for details. There is about a 1% chance of developing canaliculitis with plugs. This is a treatable infection of the tube into which the plugs are inserted.
There is evidence that supplements of omega-3 fatty acids are effective in treating some cases of dry eyes. Omega-3s are essential fatty acids - meaning that because our body cannot produce them, they are a required part of a healthy diet.
Most people don't consume enough omega-3. Some research shows that the risk for dry eye decreases with increased dietary intake of omega-3s. It has been shown that omega-3 supplements have a positive effect on the meibomian glands in your lids that secrete the oils that reduce tear evaporation. They tend to make the secretions more free-flowing.
Because of these and other studies, we recommend that patients with evaporative dry eye increase their daily intake of omega-3 fatty acids. The two best natural sources of omega-3s are dark, oily cold-water fish (e.g. salmon, sardine, mackerel) and flaxseed. To ensure an adequate dosage of omega-3 it usually has to be consumed in in a supplement form. We have found 2,000 to 3,000mg of fish or flaxseed oil daily will improve meibomian gland function. Higher doses have the potential to cause a stomach upset which can sometimes be alleviated by storing the omega-3 capsules in the refrigerator.
It usually takes 2 months of increased omega-3 intake before an improvement in symptoms will be noticed.
Further information on dry eye supplements can be found here.
Blepharitis is a common and usually chronic inflammation of the lid margins or glands. Posterior blepharitis will result in decreased secretions from the meibomian glands resulting in evaporative dry eye. This can be treated with daily hot packs and lid expression. Instructions on treatment of blepharitis can be found here.
Eyelid Blinking Exercises
Studies have found that exercises to improve the quality and rate of blinking will improve dry eye symptoms in evaporative dry eye. Instructions for eyelid blinking exercises are here.
How can I reduce my risk of dry eye syndrome?
To reduce your risk of dry eyes, take the following precautions:
- Keep your body well hydrated regularly drinking water.
- Use "floral foam" in a pot of water to humidify the room.
- Avoid alcohol and caffeine. They have a dehydrating effect.
- Run a humidifier in your home during winter or if you live in a dry climate.
- Avoid sitting adjacent to an air-conditioner or heater.
- Avoid smoking.
- Moisten your contact lenses routinely with rewetting drops.
- Clean your contact lenses daily and replace them as directed.
- Wear close-fitting sunglasses when outdoors (particularly on windy days).
- Eat salmon once a week or consider taking a daily supplement of omega-3 fatty acids.
- Check if any of your medications are likely to cause dry eye. Common medications that contribute to dry eye include classes of blood pressure medication, antihistamines, HRTs, some antidepressants and some acne medication.