Dry eye disease is one of the most common eye disorders we encounter. Prior to treatment, accurate diagnosis is important because the signs and symptoms can vary, and patients may have concomitant ocular pathology such as allergic conjunctivitis and blepharitis.
Here is a review of the available diagnostic tests for dry eye:
Questionnaires: There are a number of patient questionnaires (i.e., NEI-VFQ25, McMonnies, OSDI, DEQ, IDEEL) that are used to diagnose and monitor response to treatment. These can be time consuming and are more frequently used in studies than in clinical practice.
Schirmer’s Tests: These tests are designed to measure tear production. Schirmer’s I with anesthesia measures basal tearing (normal 10 mm or greater in 5 minutes); Schirmer’s II without anesthesia measures basal and reflex tear secretion (normal is 15 mm or greater in 5 minutes). This test is also time consuming and the results are often variable.
Phenol Red Thread Test: This test is similar to Schirmer’s test, but a special cotton thread is used instead of filter paper (normal 20 mm or greater in 15 seconds) Zone-Quick from FCI Ophthalmics is an example of this type of test.
Tear film breakup time (TFBUT, TBUT): This test measures tear film stability and is reduced (Height of Tear Meniscus: This is a measure of the tear volume. A reduced height (Ocular Surface Staining: Conjunctival staining with lissamine green or rose bengal, and corneal staining with lissamine green, rose bengal, or fluorescein represent areas of devitalized or absent cells. This test is used to assess the presence and severity of dry eye disease. Corneal Topography: Dry eye may be seen on corneal topography maps as irregularity and blank spots.
Blink Rate: Reduced blinking and/or partial blinking are associated with lipid layer deficiencies and evaporative dry eye.
Tear Film Interferometry: The LipiView device from TearScience is an ocular surface interferometer that measures the thickness of the tear film lipid layer. It also evaluates the blinking pattern.
InflammaDry Detector (Rapid Pathogen Screening): This device measures the tear level of matrix metalloproteinase-9, a marker for inflammation which is elevated in dry eye disease (> 40ng/mL). This test has 85% sensitivity and 94% specificity.
Osmolarity: The TearLab Osmolarity System detects tear osmolarity, which is increased in dry eye (>316 mOsmol/L).
Impression cytology: evaluates conjunctival goblet cell density and squamous metaplasia (rarely performed clinically).