Conjunctivitis other diagnostic studies
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sara Mehrsefat, M.D. [2]
Overview
Additional available methods for the diagnosis of keratoconjunctivitis sicca (dry eye syndrome) or superior limbic keratoconjunctivitis include corneal sensation, tear break up time, ocular surface staining and schirmer’s test.
Other diagnostic studies
Corneal Sensation
Corneal hyperesthesia or reduced sensation may be present in severe and chronic dry eye disease [3]. Sensory denervation may cause dry eye by reducing the afferent signaling of tear production, reducing the blink rate, and by altering trigeminal nerve influences on ocular epithelial health. Corneal sensation can be measured using a cotton tip applicator or more precisely with a Cochet-Bonnet esthesiometer.
Tear Break Up Time
Tear break up time (TBUT) is an indication of tear film stability. The proper method of TBUT testing is using a fluorescein-impregnated strip wet with non-preserved saline solution (benzalkonium chloride can increase tear break up speed). The dye is distributed by blinking, and the patient is then asked to stare straight ahead without blinking. The tear film is observed under the cobalt blue light of a slit lamp, and the time between the last blink and the appearance of the first dry spot or hole in the tear film is measured and equal to the TBUT.
Ocular surface staining
Interpretation of staining is based on intensity and location using a grading scale described by Van Bijsterveld. The nasal and temporal conjunctiva and the cornea are graded on a scale of 0-3 with a maximum possible score of 9. In aqueous tear deficiency, the interpalpebral conjunctiva is the most common location for rose Bengal staining. The severity of staining has been shown to correlate with the degree of aqueous deficiency, tear film instability, and reduced mucin production by conjunctival goblet and epithelial cells
Schirmer’s Test
The Schirmer test is performed by placing a paper test strip in the lateral third of the lower eyelid after drying the inferior fornix and then measuring the length of the moistened portion of the strip after 5 minutes. The Schirmer I test is performed without anesthesia and, thus, measures reflex tearing. The Schirmer II test also lacks anesthesia but is done following nasal stimulation, which has been shown to be reduced more in Sjögren’s syndrome compared to non-Sjögren’s dry eye. Schirmer with anesthesia is also commonly performed and measures basal tear secretion. The Schirmer test is often criticized for its variability and poor reproducibility. It is most useful in the diagnosis of patients with severe aqueous deficiency, but is relatively insensitive for patients with mild dry eye [