Posterior Pigmented Epithelium
The posterior pigmented epithelium of the iris, also called iris pigment epithelium (IPE), is densely pigmented and appears velvety smooth and uniform. It is continuous with the nonpigmented epithelium of the ciliary body and thence with the neurosensory portion of the retina. The polarity of its cells is maintained from embryogenesis. The basal surface of the pigmented layer borders the posterior chamber. The apical surface faces the stroma and adheres to the anterior iris epithelium (see Fig 2-22).
The posterior pigmented epithelium of the iris curves around the pupillary margin and extends for a short distance onto the anterior border layer of the iris stroma as the pigment ruff. In rubeosis iridis, the pigmented epithelium extends farther onto the anterior surface of the iris, a condition called ectropion. The term ectropion uveae, which refers to an outfolding over the pupil of the IPE, is a misnomer because the IPE is derived from neuroectoderm (not neural crest) and therefore is not considered part of the uvea.
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.