Ultrastructure of Bruch's membrane after krypton laser photocoagulation. II. Repair of Bruch's membrane and the role of macrophages.

The accompanying ultrastructural study showed that ophthalmoscopically white krypton laser photocoagulation in rats is followed by cellular invasion causing breakdown of Bruch's membrane (BM). We have expanded these observations, using scanning electron microscopy, transmission electron microscopy, and high-voltage transmission electron microscopy to describe the healing process. The repair of BM involves regenerating retinal pigment epithelial cells and choriocapillaris (CC) that form new basement membranes and fibroblasts that secrete collagen and elastin. The reformation of the CC is also associated with subretinal neovascularization. The involvement of macrophages was evident throughout the process of BM repair and formation of new vessels. We propose that the macrophages act as a common factor linking the diverse diseases associated with choroidal subretinal neovascularization, deduced from our evaluation of the healing process and the reformation of choriocapillaris.