There are many common ocular surface disorders (OSD), such as Dry Eye Disease (DED), blepharitis, and meibomian gland dysfunction (MGD), whose management requires visualization of certain ocular surface structures via slit-lamp biomicroscopy. In vivo confocal microscopy (IVCM), a more recent imaging technique has been evaluated in clinics for similar visualization.
1. Meibomian Gland Dysfunction
Meibomian glands (MG) have been classically described to compose of acini constituted by convoluted borders lined by large cells with fine cellular material within the lumen
[1], interstitial space between acini, ductules, and terminal ducts. Abnormal meibum quality and quantity can lead to a decreased or altered tear film lipid layer, tear hyperosmolarity, tear instability, and inflammation, leading to ocular surface damage and DED
[2]. Significant fibrosis (demonstrated via loss of MG architecture with extensive fibrotic tissue surrounding MG remnants) has been observed in chronic MG dysfunction
[3]. A decrease in the size of the MG acinar unit was also observed
[4]. IVCM has also been used to analyze the palpebral conjunctiva to visualize and quantify the density of immune cells
[5]. These cells have been evaluated in different locations: epithelial (EIC), intraglandular (IGIC), stromal (SIC), and periglandular (PGIC) regions. The immune cells in EIC and IGIC were increased in MGD patients with more severe dry eye symptoms, even in those with minimal corneal staining
[6]. Basal epithelial cell density was also found to be reduced with greater stromal nerve thickness in the MGD group
[7]. Hence IVCM may provide reliable and clinically relevant metrics of inflammation and serve as clinical endpoints in future clinical trials targeting inflammation in MGD.