*Current Diagnostic Tests for Dry Eye Disease in Sjögren's Syndrome DOI: http://dx.doi.org/10.5772/intechopen.103671*

However, it is possible that conjunctival inflammatory cytokines secreted in the tear film promote hyperkeratinization of the terminal duct epithelium of the meibomian gland [24]. Another process implicated in the pathophysiology of MGD in SSp may be a cytokine-induced alteration in neural-meibomian gland epithelial cell interactions. The meibomian gland is the only sebaceous gland in the human body that has elaborate sensory, sympathetic, and parasympathetic innervation. We found that parasympathetic neurotransmitters and their agonists exert a significant influence on human meibomian gland epithelial cell activity. These cells contain muscarinic acetylcholine and vasoactive intestinal peptide receptors, and the ligands of these receptors stimulate the adenylyl cyclase pathway, enhance intracellular [Ca2+], and can promote cell proliferation [85, 86].

Meibography is a diagnostic technique that allows in vivo evaluation of the morphology of the meibomian glands [87, 88]. For its evaluation, several techniques have been developed, among which are meibography with infrared light. This uses ultraviolet light to produce fluorescence of the gland, the eyelid is everted and through transillumination photographs are obtained to obtain images, which are later graded according to the loss of the meibomian glands. The classification of these images go from 0 to 3; being 0 when there is no loss, 1 when the loss of glands is less than one-third, 2 when the loss is between one-third and two-thirds and 3 when the loss is greater than two-thirds. Meibomian glands are observed differently depending on the method to evaluate them, for example, they appear as dark areas on a lighter background in the contact technique. In contrast, noncontact meibography

**Figure 8.** *Meibography.*

reveals the meibomian glands as reflected images, and the glands appear as light areas on a darker background [89]. The types of meibography that allow the capture of the morphology of the Meibomian gland in the form of photographs or films are LipiView 2; Tear Science, Cobra, LipiScan, and Tearscope [89]. The meiboscore [87] and the meibo-scale [90] are classification systems to quantify the loss of area of the meibomian gland. The meiboscores of the upper and lower eyelids are summed to obtain a total score of 0–6 for each eye [87]. In contrast, meibo-scale assigns a value from 0 to 4 for each eyelid [90]. The sensitivity and specificity for the diagnosis of MGD by noncontact meibography (cutoff value for meiboscore of +3) as a single test were found to be 49.3% and 64.5%, respectively [91]. The diagnosis of obstructive MGD based on any of the three scores (ocular symptom score, eyelid margin anomaly score, and meiboscore) resulted in a sensitivity of 100% and a specificity of 68.3%; the diagnosis based on two of the three abnormal scores yielded a sensitivity of 84.9% and a specificity of 96.7%; and diagnosis based on the fact that all three scores were abnormal yielded a sensitivity of 66.0% and a specificity of 100% (**Figure 8**) [92].
