(See also Introduction to Corneal Disorders.)
Etiology of Keratoconjunctivitis Sicca
There are 2 main types:
Aqueous tear-deficient keratoconjunctivitis sicca is most commonly an isolated idiopathic condition in postmenopausal women. It is also commonly part of Sjögren syndrome, rheumatoid arthritis (RA), or systemic lupus erythematosus (SLE or lupus). Less commonly, it is secondary to other conditions that scar the lacrimal ducts (eg, cicatricial pemphigoid, Stevens-Johnson syndrome, and trachoma). It may result from a damaged or malfunctioning lacrimal gland due to graft-vs-host disease, HIV (diffuse infiltrative lymphocytosis syndrome), local radiation therapy, or familial dysautonomia.
Evaporative keratoconjunctivitis sicca is caused by loss of the tear film due to abnormally rapid evaporation caused by an inadequate oil layer on the surface of the aqueous layer of tears. Symptoms may result from abnormal oil quality (ie, meibomian gland dysfunction) or a degraded normal oil layer (ie, seborrheic blepharitis). Patients frequently have acne rosacea.
Drying can also result from exposure due to inadequate eye closure at night (nocturnal lagophthalmos or Bell or facial nerve palsy) or from inadequate frequency of reapplication of tears to the cornea due to an insufficient blink rate (eg, in Parkinson disease).
Symptoms and Signs of Keratoconjunctivitis Sicca
Patients report itching; burning; a gritty, pulling, or foreign body sensation; or photosensitivity. A sharp stabbing pain, eye strain or fatigue, and blurred vision may also occur. Some patients note a flood of tears after severe irritation. Typically, symptoms fluctuate in intensity and are intermittent. Certain factors can worsen symptoms:
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Prolonged visual efforts (eg, reading, working on the computer, driving, watching television)
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Local environments that are dry, windy, dusty, or smoky
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Certain systemic drugs, including isotretinoin, sedatives, diuretics, antihypertensives, oral contraceptives, and all anticholinergics (including antihistamines and many gastrointestinal drugs)
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Dehydration
Symptoms lessen on cool, rainy, or foggy days or in other high-humidity environments, such as in the shower. Recurrent and prolonged blurring and frequent intense irritation can impair daily function. However, permanent impairment of vision is rare.
With both forms, the conjunctiva is hyperemic, and there is often scattered, fine, punctate loss of corneal epithelium (superficial punctate keratitis), conjunctival epithelium, or both. When the condition is severe, the involved areas, mainly between the eyelids (the intrapalpebral or exposure zone), stain with fluorescein. Patients often blink at an accelerated rate because of irritation.
With the aqueous tear-deficient form, the conjunctiva can appear dry and lusterless with redundant folds. With the evaporative form, abundant tears may be present as well as foam at the eyelid margin. Very rarely, severe, advanced, chronic drying leads to significant vision loss due to keratinization of the ocular surface or loss of corneal epithelium, leading to sequelae such as scarring, neovascularization, infections, ulceration, and perforation.
Diagnosis of Keratoconjunctivitis Sicca
Diagnosis is based on characteristic symptoms and clinical appearance. The Schirmer test and tear breakup time (TBUT) may differentiate type.
The Schirmer test determines whether tear production is normal. After blotting the closed eye to remove excess tears, a strip of filter paper is placed, without topical anesthesia, at the junction of the middle and lateral third of the lower eyelid. If < 5.5 mm of wetting occurs after 5 minutes on 2 successive occasions, the patient has aqueous tear-deficient keratoconjunctivitis sicca. With evaporative keratoconjunctivitis sicca, the Schirmer test is usually normal.
To determine the tear breakup time, the tear film is first made visible under cobalt blue light at the slit lamp by instillation of a small volume of highly concentrated fluorescein (made by wetting a fluorescein strip with saline and shaking the strip to remove any excess moisture). Blinking several times reapplies a complete tear film. The patient then stares, and the length of time until the first dry spot develops is determined (TBUT). An accelerated rate of intact tear film breakup (< 10 seconds) is characteristic of evaporative keratoconjunctivitis sicca.
If aqueous tear-deficient keratoconjunctivitis sicca is diagnosed, Sjögren syndrome should be suspected, especially if xerostomia is also present. Serologic tests and labial salivary gland biopsy are used for diagnosis. Patients with primary or secondary Sjögren syndrome are at increased risk of several serious diseases (eg, primary biliary cholangitis, non-Hodgkin lymphoma). Therefore, proper evaluation and monitoring are essential.
Several newer tests are being developed to help diagnose keratoconjunctivitis sicca. These include instruments for imaging the eyelid oil glands and measuring the quality of the tear lipid layer and tear osmolarity. Results can vary (eg, from day to day) and may correlate poorly with clinical findings. Also, an office test for ocular surface inflammation (that measures the increased matrix metalloproteinase-9 in tears) is now available. The clinical application of these tests is still uncertain.
Treatment of Keratoconjunctivitis Sicca
Frequent use of artificial tears can be effective for both types. Low-viscosity artificial tears are useful for replacing volume in aqueous tear-deficient keratoconjunctivitis sicca. More viscous artificial tears coat the ocular surface longer, and artificial tears that contain polar lipids such as glycerin or nonpolar lipids (eg, mineral oil) reduce evaporation; both types of artificial tears—viscous and lipid—are particularly useful in evaporative keratoconjunctivitis sicca. Artificial tear ointments applied before sleep are particularly useful when patients have nocturnal lagophthalmos or irritation on waking. Most cases are treated adequately throughout the patient’s life with such supplementation. Staying hydrated, using humidifiers, and avoiding dry, drafty environments can often help. Not smoking and avoiding secondary smoke are important. In recalcitrant cases, occlusion of the nasolacrimal punctum may be indicated. In severe cases, a partial tarsorrhaphy can reduce tear loss through evaporation. Omega-3 fatty acid dietary supplements may improve the oil film of the eye and be a useful adjunct in some patients.
Natural tear volume can be augmented by a device that uses soft-tip probes placed into the nose several times a day to apply electrical impulses to stimulate tear production.
Cyclosporine and lifitegrast drops that decrease the inflammation associated with dryness of the eye are available. They can lead to meaningful improvement in a fraction of patients. These drops sting and may take months before an effect is noticed.
Patients with evaporative keratoconjunctivitis sicca often benefit from treatment of concomitant blepharitis and associated acne rosacea with measures such as the following:
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For blepharitis with meibomian gland dysfunction: Warm compresses, infrared or automated heating and massaging devices, and/or systemic doxycycline 50 to 100 mg orally once or twice daily (contraindicated in pregnant or nursing patients) to help increase oil flow onto the eye surface and increase the amount of lipids in the tear film, thereby decreasing tear evaporation
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For seborrheic blepharitis: Eyelid margin scrubs and/or intermittent topical eyelid antibiotic ointments (eg, bacitracin at bedtime)
Because of the variability of symptoms, validated questionnaires can help monitor response to therapy.
Key Points about Keratoconjunctivitis Sicca
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Keratoconjunctivitis sicca is chronic, bilateral desiccation of the conjunctiva and cornea caused by too little tear production or accelerated tear evaporation.
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Typical symptoms include intermittent itching; burning; blurring, a gritty, pulling, or foreign body sensation; and photosensitivity.
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Findings include conjunctival hyperemia and often scattered, fine, punctate loss of corneal epithelium (superficial punctate keratitis) and conjunctival epithelium.
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The Schirmer test and tear breakup test may help determine whether the cause is deficient tear production or accelerated tear evaporation.
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Using artificial tears and avoiding corneal drying is usually sufficient treatment, but sometimes occlusion of the nasolacrimal punctum or partial tarsorrhaphy is indicated.
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Treatment of concomitant blepharitis is often beneficial.
