The Bruch membrane is a PAS-positive lamina resulting from the fusion of the basal laminae of the RPE and the choriocapillaris of the choroid (Fig 2-46). It extends from the margin of the optic nerve head to the ora serrata. Ultrastructurally, the Bruch membrane consists of 5 elements:
It is highly permeable to small molecules such as fluorescein. Defects in the membrane may develop in myopia, pseudoxanthoma elasticum, trauma, or inflammatory conditions and may, in turn, lead to the development of choroidal neovascularization. With age, debris accumulates in and thickens the Bruch membrane.
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.