BRUCH’S MEMBRANE (BASAL
LAMINA)
The innermost layer of the choroid, Bruch’s membrane,
fuses with the retina. It runs from the optic nerve
to the ora serrata, where it undergoes some modification
before continuing into the ciliary body.1 Bruch’s
membrane (or the basal lamina) is a multilaminated
sheet containing a center layer of elastic fibers.27 As seen
through an electron microscope, the membrane components,
from outer to inner, are the (1) interrupted
basement membrane of the choriocapillaris, (2) outer
collagenous zone, (3) elastic layer, (4) inner collagenous
zone, and (5) basement membrane of the RPE
cells1,2 (Figure 3-20). Fine filaments from the basement
membrane of the RPE merge with the fibrils of the inner
collagenous zone, contributing to the tight adhesion
between choroid and the outer, pigmented layer of the
retina.
At the ora serrata, the basement membrane of the RPE
is continuous with the basement membrane of the pigmented
epithelium of the ciliary body. The collagenous
and elastic layers disappear into the ciliary stroma, and
the basement membrane of the choriocapillaris continues
as the basement membrane of the ciliary body
capillaries.