Specular microscopy, confocal microscopy, and ultrasound biomicroscopy: Diagnostic tools of the past quarter century

Purpose. To identify, characterize, and illustrate the most important past and future potential contributions of specular, confocal, and ultrasound biomicroscopy to clinical diagnosis and research applications in the cornea from the past 25 years. Methods. Specular microscopy, in vivo tandem scanning confocal microscopy (TSCM), scanning slit confocal microscopy (SSCM), and high-frequency ultrasound biomicroscopy are examined. Results and Conclusions. This review demonstrates the abilities and limitations of three powerful new in vivo imaging modalities to resolve the cellular and structural layers of the cornea temporally and spatially in three or four dimensions, (x, y, z, t). Clinical pathological processes such as inflammation, infection, wound healing, toxicity, embryonic development, differentiation, and disease, which previously could be studied only under static ex vivo conditions, can now be dynamically evaluated over time. Thus, with continued development and application in vivo, noninvasive microscopic techniques should provide exciting new insights into understanding the structure and function of not only the eye, but also other multicellular organ systems in health and disease. These new imaging paradigms are in the first rank of advances in medical science in the past quarter century.