The basal lamina of the corneal endothelium, the Descemet membrane, is periodic acid–Schiff (PAS) positive (Fig 2-4). It is a true basement membrane, and its thickness increases with age. At birth, the Descemet membrane is 3–4 μm thick, increasing to 10–12 μm at adulthood. It is composed of an anterior banded zone that develops in utero (4.6 ± 0.4 μm thick) and a posterior nonbanded zone that is laid down by the corneal endothelium throughout life (average in adults is 11.8 ± 0.4 μm, increasing about 0.1 μm/year) (Fig 2-5). These zones provide a historical record of the synthetic function of the endothelium. Like other basal laminae, the Descemet membrane is rich in type IV collagen.
Peripheral excrescences of the Descemet membrane, known as Hassall-Henle warts, are common, especially among elderly people. Central excrescences (corneal guttae) also appear with increasing age.
Figure 2-4 Histologic section of the posterior cornea. Higher magnification depicts the Descemet membrane (D) and endothelium (En). A keratocyte nucleus (arrow) is visible in the posterior stroma.
(Courtesy of George J. Harocopos, MD.)
Figure 2-5 Corneal endothelium and the Descemet membrane.
(Illustration by Thomas A. Weingeist, PhD, 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.