**3.4 Clinical demonstration of ocular surface inflammation**

Resembling other chronic inflammatory conditions, patients with DED have inflammatory flares, typically with rapid exacerbation of symptoms such as redness, eye irritation, and blurred vision. It is postulated that acute inflammation related to DED flare begins with a nonspecific innate immune response, which is usually followed by a slower but more specific adaptive immune response [16]. Various tests are used in scientific studies and clinical practice to assess the level of ocular surface inflammation in patients. Analysis of tear film cytokines and chemokines using ELISA or LUMINEX systems, flow cytometry of conjunctival epithelial cells, impression cytology, or confocal microscopy are rather used in clinical studies. In daily practice, a simplified qualitative test of MMP-9 and lissamine green staining may be used. Lysamine green is a vital dye, which stains epithelial cells only if the cell membrane is damaged, irrespective of the presence of mucin. The result correlates with the level of inflammation on the ocular surface. Examples of ocular surface irritation are presented in **Figure 3**.

#### **Figure 3.**

*Ocular surface photos demonstrating inflammation related to DED. a. Slit lamp photo (mag. 10×). Note the visible vascularization of the eyelid margin and conjunctival superficial irritation. b. Slit lamp photo (mag. 10×, installation of lysamine green). Note the plugging of the meibomian glands, vascularization, and Marx line stained with lissamine green. c. Slit lamp photo (mag. 10×, after installation of lysamine green). A positive score of lissamine green staining in a patient with severe dry eye. d. (mag. 10×, after installation of fluorescein; blue-yellow filter applied). A positive score of fluorescein staining showed punctate keratopathy and breaks in the tear film layer.*
