The corneal endothelium is composed of a single layer of hexagonal cells derived from the neural crest (Fig 2-6). Therefore, the corneal endothelium is of neuroectodermal origin. In young adult eyes, approximately 500,000 cells are present, at a density of about 3000/mm2 centrally and up to 8000/mm2 peripherally. Mitosis of the endothelium is limited in humans, and the overall number of endothelial cells decreases with age.
The size, shape, and distribution of the endothelial cells can be observed by specular microscopy at the slit lamp. The apical surfaces of these cells face the anterior chamber; their basal surfaces secrete the Descemet membrane. Typically, young endothelial cells have large nuclei and abundant mitochondria. The active transport of ions by these cells leads to the transfer of water from the corneal stroma and the maintenance of stromal deturgescence and transparency.
Endothelial cell dysfunction and loss—through surgical injury, inflammation, or disease (eg, Fuchs endothelial corneal dystrophy)—may cause endothelial decompensation, stromal edema, and vision loss. Because endothelial mitosis is limited in humans, destruction of cells causes cell density to decrease and residual cells to spread and enlarge.
Zheng T, Le Q, Hong J, Xu J. Comparison of human corneal cell density by age and corneal location: an in vivo confocal microscopy study. BMC Ophthalmol. 2016;16:109.
Figure 2-6 Specular microscopy of living corneal endothelium. Normal endothelium is shown on the left. Note the hexagonal shape of the endothelial cells. The corneal endothelium of a patient with Fuchs endothelial corneal dystrophy is shown on the right. Demonstrated are polymegathism (larger cells), pleomorphism (variability in size and shape of cells), and dark areas of endothelial cell loss (guttae).
(Courtesy of Preston H. Blomquist, MD.)
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.