Classification and diagnosis of dry eye.

Background: Dry eye, or keratoconjunctivitis sicca (KCS), is divided into two subgroups, tear-deficient and evaporative. Each form calls for a different therapeutic approach and it is therefore essential to apply a combination of diagnostic tests in order to establish the exact diagnosis.
Material and Methods: The diagnosis of KCS is based in part on the patient's history and symptoms and in part on the application of specific tests. Several non-invasive tests exist (e.g. slit-lamp examination, meniscometry, interferometry). Mildly invasive tests are the fluorescein tests, staining with lissamine green, meibometry and meibography. Markedly invasive tests include the Schirmer test and staining with rose bengal. Additional histological procedures are the ocular ferning test and impression cytology.
Results: A combination of diagnostic tests leads to one of the two forms of KCS. Its severity is calculated according to grading systems, which exist for several tests. The longitudinal observation of the dry eye patient is provided on the basis of this same grading system, although limited reproducibility is reported for some tests.
Conclusion: The diagnostic steps for dry eye patients can be efficiently arranged. In most of the cases, non-invasive or mildly invasive tests provide an accurate diagnosis.