Ultrastructure of Bruch's membrane after krypton laser photocoagulation. I. Breakdown of Bruch's membrane
A. Pollack, G. E. Korte, A. L. Weitzner and P. Henkind
Previous observations on rats suggested that subretinal neovascularization
does not require a prior break in Bruch's membrane (BM). We verified this
observation by using scanning electron microscopy to examine large expanses
of BM that became exposed following ophthalmoscopically white krypton laser
burns. Bruch's membrane appeared intact in the acute phase after injury.
Subsequently, slitlike defects in BM were associated with penetrating
choroidal capillaries. These observations were consistent with transmission
electron microscopic findings of cellular protrusions arising from the
choriocapillary endothelial cells and from regenerating retinal pigment
epithelial (RPE) cells invading BM. These cell-formed defects in BM
differed from thermal defects in appearance, size, and onset of occurrence.
Endothelial cells penetrated all layers of BM, including the RPE basement
membrane. We conclude that endothelial cells can erode their own basement
membrane and the RPE basement membrane, and krypton laser burns with or
without immediate rupture of BM induce cellular activity that may result in
defects in BM.
