Aqueous Tear Deficiency
The clinical presentation of aqueous tear deficiency (ATD) ranges from mild ocular irritation with minimal ocular surface disease to severe and disabling disease. Patients commonly report burning, a dry sensation, photophobia, and blurred vision. Symptoms tend to be worse toward the end of the day, with prolonged use of the eyes (exacerbated by the reduced blink rate associated with computer use), or with exposure to environmental extremes (eg, lower levels of humidity associated with indoor heating or air conditioning). The clinician can quickly assess dry eye by conducting the “stare test”: after a few blinks, the patient is asked to look at a visual acuity chart; the time until the image blurs should be more than 8 seconds.
Signs of ATD include bulbar conjunctival hyperemia, a decreased tear meniscus, an irregular corneal surface, and debris in the tear film. Slit-lamp examination of the inferior tear meniscus (which is normally 1.0 mm in height and convex) is an additional, important evaluation. A significantly reduced tear meniscus is considered abnormal. Epithelial keratopathy, which can be fine and granular, coarse, or confluent, is best demonstrated following the instillation of lissamine green, rose bengal, or fluorescein dye. Rose bengal and lissamine green staining can be more sensitive than fluorescein staining in revealing early or mild cases of keratoconjunctivitis sicca (KCS) because they stain devitalized epithelium. The staining may be seen at the nasal and temporal limbus and/or inferior paracentral cornea (exposure staining). Mucous discharge is common in patients with moderate to severe ATD and in those with infectious conjunctivitis; consequently, ATD is frequently misdiagnosed as infectious conjunctivitis.
In severe ATD, filaments (strands of degenerating epithelial cells attached to the corneal surface over a core of mucus) and mucous plaques may be seen. Filamentary keratopathy can be quite painful, as these strands are firmly attached to the richly innervated surface epithelium (Fig 3-11). Marginal or paracentral corneal thinning and even perforation can occur in severe dry eye. Incomplete blinking is frequently noted. Advanced disease may also involve corneal calcification (band keratopathy), particularly in association with certain topical medications (especially glaucoma medications), and keratinization of the cornea and conjunctiva. A grading scheme for dry eye severity is presented in Table 3-4. See Chapter 2 for a discussion on tear production evaluation and tear film quantitative tests.
Patients with ATD are considered to have Sjögren syndrome if they have associated hypergammaglobulinemia, collagen vascular disease, or circulating autoantibodies (eg, SS-A, SS-B). The revised international classification criteria for Sjögren syndrome appear in Table 3-5. Although the precise causes of ATD in Sjögren syndrome are unknown, ATD is generally considered to be a T-cell–mediated inflammatory disease leading to destruction of the lacrimal glands, in part by increasing the rate of programmed cell death.
Figure 3-11 Filamentary keratopathy in a vascularized cornea.
(Courtesy of Minas T. Coroneo, MD.)
Table 3-4 Dry Eye Severity Grading Scheme
Involvement of the salivary glands is common in Sjögren syndrome, resulting in dry mouth and predisposing the patient to periodontal disease. Mucous membranes throughout the body (ie, vaginal, gastric, and respiratory mucosae) may also be affected, which would have a great impact on the patient’s quality of life.
Sjögren syndrome can be divided into 2 clinical subsets. In primary Sjögren syndrome, patients either have ill-defined systemic immune dysfunction or lack any evidence of immune dysfunction or connective tissue disease. In secondary Sjögren syndrome, patients have a well-defined, generalized connective tissue disease, most commonly rheumatoid arthritis; however, many other autoimmune and systemic diseases are associated with secondary Sjögren syndrome (Table 3-6).
Table 3-5 Criteria for the Classification of Sjögren Syndrome
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.