Doctor's Notes on Dry Eye Syndrome
Dry eye syndrome (DES) is a common problem of dry eyes. Types of dry eye syndrome are related to the underlying problem that leads to dry eyes: insufficient production of tears (also called keratoconjunctivitis sicca), poor retention of tears, or excessive evaporation of tears.
Symptoms of dry eye syndrome include dry eyes, gritty/scratchy or filmy feeling in the eyes, burning or itching in the eyes, blurred vision, vision that varies with time of day, feeling like something is in the eyes, light sensitivity and pain, excess tearing when the eyes become extremely dry or when exposed to wind, intolerance to wearing contact lenses, eye redness, and discharge or crusty material on the eyelashes. Symptoms of dry eye syndrome often worsen in dry climates, windy conditions, higher temperatures with lower humidity, and with prolonged use of your eyes (for example, reading, watching TV), and toward the end of the day.
Dry Eye Syndrome Symptoms
People with dry eyes typically experience the following symptoms and signs:
- Dry, gritty/scratchy, or filmy feeling in the eyes
- Burning or itching in the eyes
- Blurred vision
- Vision that varies with time of day
- A sensation of having a foreign body like sand in the eyes
- Light sensitivity and pain
- Excess tearing (paradoxically) when the eyes become extremely dry or when exposed to wind
- Intolerance to wearing contact lenses
- Redness of the eyes
- Discharge or crusty material on the eyelashes (when meibomian gland dysfunction is present)
Symptoms and signs often worsen in dry climates, in windy conditions, in higher temperatures with lower humidity, with prolonged use of your eyes (for example, reading, watching TV), and toward the end of the day.
Often there may be intermittent excessive tearing with dry eyes. Irritation may cause reflex tearing, in which a large amount of tears are produced all at once. The excess tears pour over your eyelids and down your cheeks. A short time later, your eyes may become irritated again, and the whole process may repeat itself.
Dry Eye Syndrome Causes
Dry eye syndrome results from problems stemming from any of three layers of the tear film (a normal, thin layer of tears that covers the eye):
- The innermost layer is the mucin (or mucus) layer. It is produced by the conjunctiva (the clear membrane that lines the eye). The mucus helps the overlying watery layer to spread evenly over the eye.
- The middle layer is the watery (or aqueous) layer. It is essentially a very dilute salty solution. The lacrimal glands located under the upper lids produce this watery layer. This layer's function is to keep the eye moist and comfortable, as well as to help flush out any dust, debris, or foreign objects that may get into the eye. It's this tear layer that flows when we're crying or when the eyes are irritated.
- The outermost layer is the oily layer. These oils are produced by the meibomian glands, which are located on the eyelids. This important layer helps block evaporation of the watery layer between blinks.
The innermost mucin layer can be abnormal if there has been injury to the conjunctiva, for example after a chemical burn, Stevens-Johnson syndrome, cicatricial pemphigoid, malnutrition, or other inflammatory or autoimmune disorders.
The middle watery layer can be insufficient if the lacrimal glands are not functioning properly. This is seen in a variety of settings, including Sjögren's syndrome, rheumatoid arthritis, or lupus and other autoimmune disorders. Some medications, including antihistamines, antidepressants, and beta-blockers, may also decrease tear production.
The eyelids can also play a role in causing dry eye syndrome if blinking is decreased or if the eyelids cannot close all the way.
- When you read, watch TV, or perform a task that requires close attention with your eyes, you may not blink as frequently. This decreased blinking allows excessive evaporation of the tears.
- Certain health conditions, such as stroke, Bell's palsy, or thyroid eye disease, can make it difficult to close your eyes on your own.
- Abnormal eyelid position following surgery, trauma, or certain skin conditions can also interfere with producing and maintaining a healthy tear film.
- Eyes can also be dry when exposed to wind from fans and vents.
When it comes to signs of eye disease, Americans are blind to the facts. A recent survey showed that while nearly half (47%) of Americans worry more about going blind than losing their memory or their ability to walk or hear, almost 30% of those surveyed admitted to not getting their eyes checked.
The following slides take a look at some of the signs and symptoms of some of the most common eye diseases.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.