A comprehensive clinical examination is the basis for selecting further diagnostic steps:
- General physical examination – including blood pressure, pulse, body weight, height; furthermore:
- Inspection (viewing).
- Skin and mucous membranes
- Eyes
- Inspection (viewing).
- Ophthalmic examination – inspection of the eyelids, testing the position of the eyelids, determination of visual acuity, slit lamp examination.
In individual cases, the following ophthalmological examinations may be required:
- Dye test – to test the tear ducts; for this purpose, dye is placed in the conjunctival sac; if the tear ducts are functioning normally, the dye should be removed after a short time (about 5 min.) and should no longer be found in the conjunctival sac.
- Fern test – qualitative testing of the tear fluid; tears from the conjunctival sac are applied to a slide with the help of a glass spatula and allowed to dry at room temperature; after about ten minutes, the crystallization pattern (fern phenomenon) of the tear fluid is assessed under the microscope.
- Control of the tear drainage
- Measurement of tear film osmolarity
- Schirmer test – to measure the amount of tear production; for this purpose, a 5-mm-wide and 35-mm-long filter paper strip (litmus paper) is inserted into the conjunctival sac at the outer corner of the eyelid; after 5 minutes, the distance that the tear fluid has traveled in the paper strip is read; xerophthalmia (decreased tear production) is present when the distance is < 10 mm
- Tear film break-up time (also BUT after break-up time) – measure of tear film stability; for this purpose, the tear film is stained with fluorescein; then the tear film is observed through the slit lamp and the time is measured simultaneously. In this way, it is possible to see when the tear film breaks up. The normal time is more than 15 seconds in the healthy eye.
