2020–2021 BCSC Basic and Clinical Science Course™
Chapter 4: Clinical Evaluation and Imaging of the Anterior Segment
Anterior Segment Imaging
Specular microscopy (Fig 4-14B) is discussed in BCSC Section 8, External Disease and Cornea. The technique allows noncontact, noninvasive imaging of the corneal endothelial cell layer. Most commercially available devices automatically identify the endothelial cells and analyze the images to provide the user with quantitative assessments of the endothelial cell density (ECD) and morphology. ECD is often monitored in the context of clinical trials of surgically implanted devices such as aqueous drainage devices and stents. The US Food and Drug Administration (FDA) has advised monitoring ECD in eyes with the CyPass Micro-Stent, a suprachoroidal stent that was recalled by the FDA (see Chapter 13).
Figure 4-14 Iridocorneal endothelial syndrome. A, Slit-lamp view, with mild distortion of the inferior iris and peripheral anterior synechiae. B, Specular microscopy images of the same patient. The right-eye image discloses tightly packed endothelial cells with a normal hexagonal shape, while the left-eye images reveal endothelial cells that are reduced in number and pleomorphic. Many cells exhibit a dark specular reflex.
(Courtesy of Angelo P. Tanna, MD.)
Specular microscopy is useful for the diagnosis and monitoring of various posterior corneal disorders such as posterior polymorphous dystrophy and iridocorneal endothelial syndrome. The latter is a rare condition in which corneal endothelial cells proliferate and migrate beyond the Schwalbe line and anterior chamber angle, onto the iris. Secondary angle-closure glaucoma ensues as this cellular membrane contracts (see Chapter 10). In this disease the endothelial cell count is reduced, and the cells lose their normal hexagonal shape (see Fig 14-4).
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.