Diagnostic Tests

Dry Eye Tests

A thin strip of fitler paper is used in this test. The paper is placed just below the lower eyelid and left there for 5 minutes. The paper is then removed and the amount of wetness is measured. More than 10mm wetness on the paper is evaluated as the normal amount of tears, whereas less than 5mm is a finding of dry eye. An often used method in the determination and quality of dry eye is the tear film paper breaking time measurement.

Figure 1. The Schirmer test (left) and  tear film osmolarity test (right) to evaluate dry eye disease.

The tear film paper is held on the cornea with the eye open and not blinking, then after a period of time it braks at some points. One drop of fluorescein is administered to the eye during this test. Before the test, the patient is told to blink several times then to keep completely still. At this point, the tear film layer of the eye is evaluated under biomicroscopy. If the tear breaking time is shorter than 10 seconds, this is an indicator of dry eye and shows that the quality of the tear function is impaired.

Figure 2. Tear breakup time (TBUT) is a clinical test used to assess for evaporative dry eye disease.