Keratoconjunctivitis sicca is dryness of the conjunctiva (the membrane that lines the eyelids and covers the white of the eye) and cornea (the clear layer in front of the iris and pupil).
Too few tears may be produced, or tears may evaporate too quickly.
The eyes become irritated and sensitive to light and usually burn and itch.
Tear production may be measured by placing a strip of paper at the edge of the eyelid.
Artificial tears and sometimes punctal plugs (which fit into the puncta, the small openings at the inner corners of the eyelids near the nose) help relieve symptoms.
Causes of Keratoconjunctivitis Sicca
There are 2 main types (although many patients have components of both types):
Aqueous tear-deficient dry eyes
Evaporative dry eyes
Dry eyes may be due to inadequate tear production (aqueous tear-deficient dry eyes). With this type of dry eyes, the tear gland (lacrimal gland) does not produce enough tears to keep the entire conjunctiva and cornea covered by a complete layer of tears. (See figure Structures That Protect the Eye.) This is the most common type among postmenopausal women. Dry eyes are common in Sjögren syndrome. Rarely, aqueous tear-deficient dry eyes may be a symptom of diseases such as rheumatoid arthritis or systemic lupus erythematosus (lupus). Certain medications may contribute to aqueous tear-deficient dry eyes. These include diuretics, anticholinergics, antidepressants, beta-blockers, antihistamines, and decongestants.
Dry eyes may also be due to an abnormality of tear composition that results in rapid evaporation of the tears (evaporative dry eyes
Drying can also result from the eyes being partly open for periods of time at night (nocturnal lagophthalmos) or from an insufficient rate of blinking (as can occur in Parkinson disease). Some antipsychotics, adrenergic agonists (certain antihypertensives), and botulinum toxin injections can all aggravate dry eye due to nocturnal lagophthalmos.
Structures That Protect the Eye
Symptoms of Keratoconjunctivitis Sicca
Symptoms of dry eyes include irritation, burning, a pulling sensation, pressure behind the eye, and grittiness or a feeling as if something is in the eye (foreign body sensation). Sometimes blurred vision that comes and goes is also present. Damage to the surface of the eye increases discomfort and sensitivity to bright light. Symptoms are worsened by
Activities in which the rate of blinking is reduced, specifically those that involve prolonged use of the eyes, such as reading, working at a computer, driving, or watching television
Windy, dusty, drafty, or smoky areas and dry environments, such as in airplanes or in shopping malls; areas with low humidity; and areas where air conditioners (especially in the car), fans, or heaters are being used
Symptoms lessen during cool, rainy, or foggy weather and in humid places, such as in the shower.
Blinking spreads more tears on the surface of the eye, reducing or preventing dryness and symptoms. Frequent blinking is often done to relieve dryness.
Even with the most severe dry eyes, it is rare that vision is lost. However, people sometimes feel that their blurred vision or eye irritation is so severe, frequent, and prolonged that it is difficult to function normally. In some people with severe dryness, the surface of the cornea can thicken, or ulcers and scars can develop. Occasionally, blood vessels can grow across the cornea. Scarring and blood vessel growth can impair vision.
Diagnosis of Keratoconjunctivitis Sicca
Schirmer test and tear breakup test
Doctors diagnose dry eyes by the symptoms and appearance of the eyes and by doing some tests. Both tests are done before instilling drops of any kind.
Doctors examine the eyes with a slit lamp
The Schirmer test—in which a strip of filter paper is placed at the edge of the eyelid—is used to measure the amount of tears produced during the next 5 minutes.
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They may also measure how long it takes for the eye to become dry when the person stares (called the tear breakup time).
Treatment of Keratoconjunctivitis Sicca
Artificial tears
Punctal plug
Artificial tears applied every few hours can generally control the problem. Artificial tears are eye drops prepared with substances that simulate real tears and help keep the eyes coated with moisture. Lubricating ointments applied before bed last longer than artificial tears and help prevent dryness in the morning. Such ointments are not usually used during the day because they may blur vision. Some doctors may recommend omega-3 fatty acid dietary supplements to improve the oil film of the eye, but most evidence indicates that these do not help.
An ophthalmologist (a medical doctor who specializes in the evaluation and treatment―surgical and nonsurgical―of eye disorders) can do a minor in-office procedure to help people with dry eyes. During the procedure, an ophthalmologist inserts plugs into the puncta (the small openings at the inner corners of the eyelids near the nose) to keep tears from leaving the eye by blocking the flow of tears off of the eye surface, through the tear duct, and into the nose. This way more tears are available for longer to bathe the eyes. In people with extremely dry eyes, the eyelids may be partially sewn together to decrease tear evaporation. In severe cases, the tear duct can be sealed shut.
A special nasal spray can also be used twice a day to stimulate tear production.
If a person has blepharitis, it is treated with measures such as warm compresses, massage and heating devices, eyelid scrubs, and sometimes oral antibiotics.
