Biosensing Critical Markers of the Ocular Surface Microenvironment: Evolution and Frontiers.

The ocular surface microenvironment (OSM), which is regulated by the lacrimal functional unit and the external environment, is highly dynamic and determines the health of the ocular surface (OS). In this review, we first highlight the importance of physiological parameters, namely, oxygen tension, osmolarity, and pH of the OSM on the health of the OS. The mechanisms leading to their imbalance and consequent dysfunctions of the ocular tissues are discussed next. Understanding the pathophysiology of these disorders for the development of treatment modalities requires tools for accurate, sensitive, and rapid measurement of the physiological parameters in a clinical setting. Thus, we review existing strategies for sensing OSM. The challenges have been analyzed, and insights into how recent development of microfluidic contact lens-based technology, nanotechnology, and other novel technologies enable OS biosensing, in general, are provided using examples. We also identify the need for accurate and sensitive in vivo diagnosis of antigens, proteins, and other physiological factors of the OSM. Finally, we provide a future perspective on the development of fluorescence spectroscopy- and nanotechnology-based, wearable, point-of-care devices and techniques for the diagnosis of OSM.