What tests are used to document dry eyes in a patient with suspected primary Sjogrens Syndrome?
The three most common tests for dry eyes include the Schirmer’s test, ocular surface staining (OSS) , and tear break-up time (TBUT) . For the Schirmer’s test, a piece of filter paper is placed under the inferior eyelid without anesthesia and the amount of wetness is measured. Normal wetting is >15 mm in 5 minutes, whereas <5 mm meets one of the classification criterion for SS. There is a 15% false-positive and false-negative rate with Schirmer’s testing.
The remaining tests are performed by an ophthalmologist using a slit-lamp examination. OSS is performed using a sequential examination with fluorescein dye for the cornea, followed by lissamine green dye to assess the conjunctiva. Fluorescein dye targets areas of cellular disruption (indicating dryness severe enough to cause corneal epithelial injury), whereas lissamine green dye stains conjunctival epithelial surfaces that have been damaged or devitalized. Staining uptake is typically maximal along the palpebral fissure, where maximum exposure to the environment and evaporation of tears occurs. The OSS is the sum of a 0-6 score for fluorescein staining of the cornea and a 0-3 score for lissamine green staining of both the nasal and temporal bulbar conjunctiva (total score 0-12). An OSS ≥5 in at least one eye meets one of the classification criterion for SS. TBUT measures disruption in tear film and indicates an abnormal mucus layer if the tear film is ≤10 seconds. These tests have largely replaced the Rose Bengal stain, which is used less commonly due to toxic effects on corneal epithelial cells
