Dry eye disease pathogenesis and clinical signs: searching for correspondence in the clinical practice

Ocular surface alterations causing dry eye disease (DED) can be described as a vicious circle consisting of different consecutive stages. Among the factors involved, the ocular surface immune-inflammatory response has been established as a key player in the pathogenesis of the vicious circle of DED. Thus, the prompt recognition of the disruption of the immunoregulatory mechanisms is crucial for properly managing the ocular surface alterations. To increase awareness and knowledge of the identification and clinical interpretation of immunological mechanisms of dry eye in clinical practice, we present two clinical cases related to DED patients to provide a practical example of clinical examination application and interpretation of diagnostic parameters in daily practice. Moreover, a literature overview of the available clinical examinations to assess the immunological involvement in DED patients, with a particular focus on the correlation between diagnostic parameters and pathogenesis of clinical signs, is provided with an educational intent.

The presented clinical experiences suggested that in ocular surface pathologies, knowledge of the immune-inflammatory pathogenetic mechanisms underlying the observed clinical sign is of great help for understanding what is being observed in the patient and, consequently, for the choice of appropriate therapy. Literature evidence suggests that many different clinical examinations can be used to assess inflammation in DED patients, such as the assessment of hyperemia, staining of the ocular surface and measurement of hyperosmolarity and MMP-9 levels. The combination of impression cytology and flow cytometry to assess for markers of inflammation is considered the best technique to quantify the level of inflammation on the ocular surface, even if not always applicable in clinical practice.

Literature evidence and clinical experiences suggest that basic diagnostic approaches (assessment of hyperemia, MMP-9 levels, and staining of the ocular surface with Lissamine green or fluorescein) represent useful tools to assess the inflammatory component of DED in everyday practice, providing a guide to establish the correct therapeutic strategy.