The Role of Scanning Electron Microscopy in the Evaluation of Conjunctival Microvilli as an Early Biomarker of Ocular Surface Health: A Literature Review.

Microvilli are bristle-like protuberances of the plasma membrane, which express the vitality of mucous and epithelial cells; their alteration indicates a condition of cellular suffering in a predictive sense, making it possible to establish how much an inflammatory state or toxic conditions affect cellular functionality. In this article, the authors evaluate the applications of scanning electron microscopy (SEM) examination to impression cytology (IC) of the bulbar conjunctiva for the assessment of microvillar alteration as an early ultrastructural indicator of ocular surface health. This method offers several advantages, starting with its simplicity: it involves the non-invasive application of a strip of bibulous paper to the bulbar or tarsal conjunctiva. Unlike conjunctival or corneal biopsies, which are surgical procedures, this technique is far less invasive and more comfortable for the patient. It also provides a more clinically relevant in vivo assessment compared to studies on cultured cell lines, which are mostly limited to scientific research and may not accurately reflect real-world conditions. This makes it an effective, repeatable, and patient-friendly option for detecting early pathological alterations of the ocular surface. It also represents a useful tool for evaluating the efficacy of topical drugs and the toxic effects of external factors and ophthalmic or systemic diseases. Finally, it allows for obtaining accessory information relating to goblet cells, the presence of inflammatory infiltrate, or any pathogens.