Dry Eye Syndrome Workup

Conjunctival impression cytology can be used to monitor the progression of ocular surface changes.

Serology for circulating autoantibodies, including ANA or SS antibodies (ie, SS-A, SS-B), anti-Ro, anti-La, anti-M3 receptor, and anti-fodrin, as well as ANCA and Rh-F, may be indicated.

Dry eye is essentially a clinical diagnosis, combining information obtained from both the history and the examination and performing 1 or more tests to lend some objectivity to the diagnosis. No one test is sufficiently specific to permit an absolute diagnosis of dry eye.

Symptom questionnaires can be used to help establish a diagnosis of dry eye and to assess the effects of treatments or to grade disease severity. Fourteen ideal questionnaires are available in Pubmed.

Tear break-up test (TBUT) is determined by measuring the time lapse between instillation of fluorescein and appearance of the first dry spots on the cornea. Measure it prior to instillation of any anesthetic eye drops. A fluorescein strip is moistened with saline and applied to the inferior cul-de-sac. After several blinks, the tear film is examined using a broad-beam of slit lamp with a blue filter for the appearance of the first dry spots on the cornea. Decreased TBUT of less than 10 seconds is considered abnormal, indicative of tear instability.

Use rose bengal and fluorescein staining to evaluate epitheliopathy. Rose bengal stains not only dead and devitalized cells but also healthy cells that are protected inadequately by a mucin coating. Fluorescein pools in epithelial erosions and stains exposed basement membrane. Generally, it stains the cornea more than the conjunctiva. Lissamine green B and sulforhodamine also have been used as staining agents.

Early or mild cases of KCS are detected more easily with rose bengal than with fluorescein staining, and the conjunctiva usually is stained more intensely than the cornea. Interpalpebral staining of the nasal and/or inferior paracentral cornea is seen in KCS. A linear pattern of inferior conjunctiva and corneal staining by rose bengal is characteristic of meibomian gland dysfunction.

Van Bijsterveld developed a scoring system for rose bengal that evaluates the intensity of staining based on a scale of 0-3 in 3 areas: nasal conjunctiva, temporal conjunctiva, and cornea. With this system, the maximum possible score is 9. According to this system, a score of 3.5 or greater is considered positive for KCS.

Lissamine green staining combines the advantages of fluorescein and rose bengal staining; it stains healthy epithelial cells that are not protected by a mucin layer (similar to rose bengal) and also stains degenerating or dead cells (similar to fluorescein). It avoids the pain, discomfort, and corneal toxicity associated with rose bengal but is somewhat less sensitive and more transient, so it is more difficult to appreciate on slit lamp examination.

Use the Schirmer test to test aqueous tear production. It is performed by placing a thin strip of filter paper in the inferior cul-de-sac; then, the eyes are closed for 5 minutes, and the amount of wetting of the paper strip is measured. Traditionally, the basic secretion test is performed following the instillation of topical anesthetic and the placement of a thin strip of filter paper in the inferior cul-de-sac. The authors prefer this technique and use the corners of soft tissue to wick, by capillary attraction (without any wiping action), all liquid from the inferior fornix prior to placement of the Schirmer paper. Measurement of less than 5 mm is abnormal; 5-10 mm is equivocal.

The Schirmer I test, which measures both basic and reflex tearing, consists of the same test without the use of a topical anesthetic agent. Less than 10 mm of wetting after 5 minutes is diagnostic of aqueous tear deficiency. The test is relatively specific, but it is poorly sensitive.

The Schirmer II test measures reflex tearing. It is performed similar to the basic secretion test, with the addition of nasal mucosal irritation with a cotton tip applicator. Wetting of less than 15 mm after 5 minutes is consistent with abnormalities of reflex secretion.

Absence of nasal lacrimal reflex tearing, presence of serum autoantibodies, and severe ocular surface disease demonstrated by rose bengal or fluorescein staining argues strongly in favor of a diagnosis of SS associated KCS.

Additional tests may be performed to quantify each individual tear component. Lipids may be tested for by collecting meibum, either by squeezing the eyelid margin to encourage expression from the meibomian glands or by using sterile curettes to suck meibum from individual gland orifices. They may be analyzed by high pressure liquid chromatography (HPLC) or gas chromatography with mass spectroscopy (GC-MS).

The aqueous/protein component may be tested for by measuring the tear film osmolarity, tear lysozyme, tear lactoferrin, EGF, aquaporin 5, lipocalin, and IgA concentrations with ELISA. Tear film osmolarity has been shown to be elevated in patients with dry eyes. It is a very sensitive test for identifying a dry eye but lacks specificity in meibomitis, herpes simplex keratitis, and bacterial conjunctivitis. The test often is not used because of the lack of commercially available equipment for its measurement.

Mucins may be analyzed by using impression cytology or brush cytology techniques, which obtain epithelial and goblet cells that can then be tested for mucin mRNA expression. Immunofluorescence, flow cytometry, ELISA, or immunoblotting techniques may also be used.

Conjunctival biopsy for in situ hybridization and immunohistochemistry may also be used.

The tear stability analysis system (TSAS) is a noninvasive and objective test that is used to help diagnose tear film instability.

Tear evaporation is tested by evaporimetry.

The tear function index (TFI) (Liverpool modification) evaluates the tear dynamics of production and drainage and helps detect subjects suffering from dry eye. The test depends on using prepared filter paper strips containing fluorescein, and it has been designed to allow the direct measurement of the TFI using the prepared tear strips.

The tear ferning test (TFT) can be used to help diagnose the quality of tears (electrolyte concentration), KCS, and hyperosmolarity. A drop of tears is collected from the lower meniscus and then placed onto a microscope slide and allowed to dry by evaporation. Different forms of branching crystallization patterns can be observed and classified. This test permits the separation of healthy eyes from dry eyes on the basis of the ferning patterns.

Impression cytology: In mucin layer deficiency, the epithelium may undergo squamous metaplasia, resulting in a loss of goblet cells. This method is very sensitive but requires proper staining and expert analysis of the slide.

Meibography/meiboscopy: Meibomian gland morphology and density and dropout may be analyzed by using meibography/meiboscopy to help diagnose meibomian gland dysfunction. Meiboscopy is the visualization of the meibomian gland by transillumination of the eyelid. Meibography implies photographic documentation.

Meibometry: Meibomian gland dysfunction may be diagnosed by meibometry. Lipid on the lower central lid margin is blotted onto a plastic tape, and the amount taken up is read by optical densitometry. This provides an indirect measure of the steady state level of the meibomian lipid.

Meniscometry (tear meniscus radius, height, and cross-sectional area): Meniscometry is used to help diagnose aqueous tear deficiency. A rotatable projection system with a target comprising black and white stripes is projected onto the lower central tear film meniscus. Images are recorded and then transferred to a computer to calculate the radius of curvature.

Patients with dry eye have reduced central corneal thickness values. This is thought to somehow result from the hypertonicity of the tear film in these patients. The corneal thickness increases after therapy with artificial tears, and this has been suggested as a new diagnostic and follow-up criterion for dry eye. Visual acuity and corneal topography and keratometry readings have been shown to improve after the use of artificial tears.

Additionally, on the matter regarding hypertonicity of tears of patients with dry eye disease, measurement of tear osmolarity has been proposed as a “new” diagnostic modality in the assessment of patients suspected of having dry eye disease. Gilbard et al may have been the first to assess and promote this idea 33 years ago.^[6]

More recently, Lemp and associates conducted a multicenter, 10-site study using 314 consecutive subjects between age 18 and 82 years , including a comparison of many of the other diagnostic strategies described above.^[7] Tests performed were bilateral tear osmolarity, tear film break-up time (TBUT), corneal staining, conjunctival staining, Schirmer test, and meibomian gland grading. A composite index of objective measurements was used to gauge diagnostic performance, which classified subjects as having normal, mild or moderate, or severe dry eye. The primary outcome measures were sensitivity, specificity, area under the receiver operating characteristic curve, and intereye variability.

Results showed that tear osmolarity had superior diagnostic performance. Between normal and mild or moderate subjects, the most sensitive threshold was 308 mOsms/L, while the most specific was 315 mOsms/L. Tear hyperosmolarity showed 73% sensitivity and 92% specificity at a cutoff of 312 mOsms/L. Poor sensitivity (corneal staining, 54%; conjunctival staining, 60%; meibomian gland grading, 61%) or poor specificity (tear film break-up time, 45%; Schirmer test, 51%) was shown by the other tests. Also, tear osmolarity had the highest area under the receiver operating characteristic curve (0.89). Increasing dry eye disease severity was correlated with intereye differences in osmolarity. The authors concluded tear osmolarity is the best single metric to diagnose and to classify dry eye disease.

The tear turnover rate, defined as the percentage decrease of the fluorescein concentration in tears per minute after instillation, is also reduced in patients with symptomatic dry eye. It is tested by using fluorophotometry.

Lacrimal gland or minor (salivary) gland biopsy may be performed to aid in diagnosing SS.

Histopathologically, squamous metaplasia with loss of goblet cells, cellular enlargement, and increase in cytoplasmic/nuclear ratio of the superficial conjunctival epithelial cells are present in patients with KCS. The lacrimal gland and the conjunctiva are also heavily infiltrated by CD4⁺ T cell (and B cell) lymphocytes.

In meibomian gland dysfunction, loss of glandular architecture, dilation of the ductules, ductal occlusion, and hyperkeratinization of the ductal epithelium are seen.