Specular microscopy is a modality for examining endothelial cells that uses specular reflection from the interface between the endothelial cells and the aqueous humor. The technique can be performed using contact or noncontact methods. In both methods, the instruments are designed to separate the illumination and viewing paths so that reflections from the anterior corneal surface do not obscure the weak reflection arising from the endothelial cell surface.
As we learned earlier, endothelial cells can also be visualized through a slit-lamp biomicroscope, if the illumination and viewing axes are symmetrically displaced on either side of the normal line to the cornea (see Fig 8-11D). A narrow illumination slit must be used; hence, the field of view is narrow.
Contact specular microscopy allows for higher magnifications than slit-lamp biomicroscopy, making cellular detail and endothelial abnormalities more discernible and allowing for cell counting as well as the study of morphology (see also BCSC Section 8, External Disease and Cornea).
Excerpted from BCSC 2020-2021 series : Section 3 - Clinical Optics. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.