Dry eye testing can be done with Schirmer’s and BUT tests.
Schirmer’s test
This test is used when there is doubt if the patient suffers from a syndrome of decreased tear production. The process consists of measuring the amount of moisture on a small strip of filter paper 5 mm wide and 35 mm long. The test can be done with or without previously putting anesthetic into the cornea. Without anesthetic, the doctor measures total tear secretion – basal and reflex. With anesthetic, only basal secretion is measured. Before placing the paper, it is necessary to gently dry the eye. The filter paper is placed between the middle and the outer third of the lower eyelid. After 5 minutes, the amount of moisture is measured. A normal result is over 15 mm without anesthesia and about 10 mm with anesthesia. The lower border of tear secretion is 6 mm.
BUT test (Tear breakup time test)
This clinical test is used to estimate the quality of the tear film. It is done by dropping fluorescein (a special orange color) into the eye and asking the patient not to blink. Then the doctor looks at the tear film through a microscope and notes the time that passes from the last blink till the first crack of color appears on the surface of the tear film. If the time is shorter than 10 seconds, it is considered there is the instability of tear film.