Keratoconjunctivitis sicca other diagnostic studies

Dry eyes can usually be diagnosed by the symptoms alone.^[1] Tests can determine both the quantity and the quality of the tears. A slit lamp examination can be performed to diagnose dry eyes and to document any damage to the eye.^[1]

A Schirmer’s test can measure the amount of moisture bathing the eye.^[1] This test is useful for determining the severity of the condition.^[2] A five-minute Schirmer’s test with and without anesthesia using a Whatman #41 filter paper 5 mm wide by 35 mm long is performed. For this test, wetting under 5 mm with or without anesthesia is considered diagnostic for dry eyes.

If the results for the Schirmer’s test are abnormal, a Schirmer II test can be performed to measure reflex secretion. In this test, the nasal mucosa is irritated with a cotton-tipped applicator, after which tear production is measured with a Whatman #41 filter paper. For this test, wetting under 15 mm after five minutes is considered abnormal.

A tear breakup time (TBUT) test measures the time it takes for tears to break up in the eye.^[2] The tear breakup time can be determined after placing a drop of fluorescein in the cul-de-sac.

A tear protein analysis test measures the lysozyme contained within tears. In tears, lysozyme accounts for approximately 20 to 40 percent of total protein content.

A lactoferrin analysis test provides good correlation with other tests.

Recently it was described a molecule – Ap4A- which is intrinsic component of the tears. The presence of this molecule is abnormally high in different states of the ocular dryness. This molecule could quantifyied biochemically simply taking one tear sample with a plain Schirmer test. Utilizing this technique is possible to determine the concentrations of Ap4A in the tear of the patients and such way to diagnose in an objective way if the samples are corresponding to dry eye^[3].

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