This thesis is dedicated to my grandparents

Figure 9
Transverse section through the posterior wall of the eye, showing BrM in between the retina and the bloodvessels of the
choroid. Adopted from the American Health Assistance Foundation
Histologically, BrM consists of 5 layers:
1/ the RPE basal lamina
2/ the inner collagenous zone, consisting of collagens type I, III and VI
3/ the middle elastic zone, which forms a unique interlacing network with the inner and
outer collagen fibrils, differing from elastin structures in the skin and bloodvessels. This
maze-like structure is considered to play a role in the integration of the various ECM
components into one functional unit.
4/ an outer collagenous zone
5/ the basement membrane of the endothelial cells of the choroid
In addition to the collagenous and elastic components, BrM contains a variety of
proteoglycans (heparin, dermatan, chondroitin sulphate), which may be involved in the structural
and functional properties of BrM, as they are suggested to make up anionic sites acting as charge
barriers [98-100].
b/ histopathology of Bruch membrane
The changes in BrM are apparently identical to those seen in the middermis, with similar
calcium deposits onto and clumping of fragmented elastic fibres. As a result, the barrier
membrane will no longer have a smooth surface, but will start to exhibit breaks (Figure 10),
making it possible for choroid vessels to grow towards the inner retina. The start of this
degradation is characterized by discontinuities in the middle elastic layer and loss of RPE
pigment granules. In a next stage, full thickness breaks in combination with atrophy of the
overlying RPE and photoreceptor cells are observed plus ruptures of the underlying choroid. In
some cases, herniation of choroidal fibrillar collagen tissue and choriocapillaris in to the breaks in
BrM can be seen, separating this membrane. Surprisingly, no histological data on peau d’orange
or comet tails (see paragraph ‘d’) could be found.
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