Understanding Dry Eye
Typical symptoms for people suffering from dry eyes are burning, irritation, blurred vision, and (ironically) tearing. Dry eyes can be caused by decreased tear production or increased tear evaporation, or a combination of both. Some diseases and some medications may also contribute to dry eyes. Fortunately, there are a number of treatments to help with dry eyes.
The tear film is comprised of 3 layers: a mucous layer, an aqueous (water) layer and an oil layer. If there is a deficiency in any one of these layers dry eye can occur.
Dry Eye Treatment
Dry eye can be identified on exam using a slit lamp biomicroscope by your ophthalmologist. Your eye physician may evaluate the stability of the tear film by applying a special dye to the surface of your eye to see how long it takes for the tear layer to break apart. This is called ‘tear break-up time’ and is considered normal when the tear film remains stable for over 10 seconds. An abnormal tear break-up time is seen in all forms of dry eye. To determine if your eyes are producing enough tears your eye physician may perform Schirmer testing by applying special filter paper to your eye to see how much liquid can be wicked away over 5 minutes. If this test is abnormally low then aqueous tear deficiency dry eye is present.
Meibomian Gland Dysfunction
Evaporative Dry Eye
Evaporative dry eye occurs when the oil layer of the tear film is deficient. Oil is produced in small glands in the eyelid called meibomian glands. There are many conditions and factors that affect the health of the meibomian glands that can lead to a reduction in oil production or thickened oil secretions. Evaporative dry eye is often referred to as meibomian gland dysfunction or blepharitis. Symptoms of evaporative dry eye include burning and irritation, redness, foreign body sensation and fluctuating blurred vision. These symptoms are often exacerbated by activities that require visual attention such as prolonged reading, working at the computer, watching television or driving. These symptoms may also be exacerbated by environmental factors such as low humidity and wind.
Aqueous Tear Deficiency Dry Eye
Aqueous tear deficiency dry eye occurs when there is a reduction in the aqueous component of the tear film. The aqueous component of the tear film is produced by lacrimal glands near the surface of the eye and is essential to maintaining a healthy tear film. Tear production from these glands can be affected by medications commonly used to treat conditions such as seasonal allergies, hypertension or depression among others. Certain systemic inflammatory conditions can also affect the lacrimal glands of the eye leading to a reduction in aqueous tear production.
Aqueous Tear Deficiency
Dry Eye Treatment
Treatment for dry eye is directed by the underlying cause of the ocular surface dryness: too much evaporation or too little tear production.
- For evaporative dry eye the aim is to improve the function of the meibomian glands and the quality of the oil component of the tear film. The mainstay of treatment is twice daily eyelid hygiene regimen consisting of gentle eyelid scrubs and hot compresses with eyelid massage. Depending on severity or associated medical conditions, pills or eye drop medications may be recommended to reduce inflammation of the meibomian glands and ocular surface. Artificial tears are also helpful to reduce symptoms.
- In aqueous tear deficiency dry eye the focus of treatment is increasing the amount of aqueous tears available on the surface of the eye. This can be accomplished by applying artificial tear eye drops to replace deficient tears. In mild disease artificial tear drops alone are often enough to improve symptoms. In more advanced disease, your doctor may recommend blocking the drainage of tears off the surface of the eye by inserting a small plug called a punctal plug into the tear drainage system. Alternatively, or in addition, your doctor may recommend an eye drop medication to improve tear production.
Methods of Treatment
The mainstay of treatment for evaporative dry eye caused by meibomian gland dysfunction or blepharitis is twice daily gentle eyelid scrubs and hot compresses with eyelid massage. The eyelid scrubs help to remove debris at the opening of the meibomian glands allowing them to function better.
The scrubs are best performed with a gentle cleanser applied to the eyelid margin with a cotton swab. Many eye doctors recommend baby shampoo but I prefer a gentle fragrance and dye free cleanser such as Cerave® Hydrating Cleanser or Cetaphil® Gentle Skin Cleanser since they are less irritating to the eye & eyelid skin.
The gentle eyelid scrub should be followed by a hot compress with eyelid massage. The hot compress should be performed with a clean washcloth that has been soaked in hot tap water then wrung to remove excess water. Apply the washcloth to both eyelids for a minimum of 4 minutes to melt the oil inside the glands. Alternatively, a heat pack can be used to heat the eyelid. A special eye mask heat pack can be purchased over-the-counter at your local drug store or a homemade version can be fashioned by filling a clean sock with dry rice. The heat pack is then heated in the microwave prior to application to the eyelid. Be sure to follow the instructions on the commercially available eye mask to avoid burning your eyelid skin. After the eyelids have been heated, massage along the length of the meibomian gland to squeeze oil out onto the surface of the eye. This is accomplished by stroking in a vertical and downward motion toward the eyelashes.
Eye Drop Medications
Inflammation caused by dry eye can damage the surface of the eye and affect the lacrimal glands that produce aqueous tears. Anti-inflammatory medications such as topical steroid eye drops or cyclosporine A (Restasis®) have been shown to improve dry eye symptoms and increase tear production. Your eye doctor may recommend a short course of steroids while starting other treatments. Cyclosporine A (Restasis®) is an anti-inflammatory eye drop that can increase tear production in individuals with aqueous tear deficiency dry eye resulting in improved dry eye symptoms.
Artificial tears are an important treatment option for both evaporative and aqueous tear deficiency dry eye. There are many different types and brands of artificial tears. Generally, you should know that artificial tears come in preserved and non-preserved forms. Preservatives in eye drops can become irritating to the eye if the eye drop is used frequently. If you find that you need to apply artificial tears more than 4 times daily, then a preservative free formula is preferred. Preservative free drops are packaged in individual use vials and can be used multiple times in 24-hour period before they should be discarded.
The amount of aqueous tears available to moisten the surface of the eye is determined by a delicate balance of tear production by the lacrimal glands and tear drainage through the lacrimal drainage system. In aqueous tear deficiency dry eye, one treatment strategy is to reduce the amount of tears leaving the surface of the eye by plugging one or both drains that drain tears away from the eye. This treatment involves a minor office procedure where a small plug (called a ‘punctal plug’) is inserted into the opening, or punctum, of the lacrimal drainage system.