Ultrastructural immunocytochemistry of subretinal neovascular membranes in age-related macular degeneration.

BACKGROUND

The authors studied various cellular and extracellular matrix components of subretinal neovascular membranes (SRNVM) from patients with age-related macular degeneration (ARMD).

METHODS

Electron microscopic immunocytochemistry was used on the subfoveal neovascular membranes surgically removed from three patients with disciform lesions due to ARMD.

FINDINGS

The SRNVMs always contained large "feeder" vessels along with many new capillaries in different stages of maturation. Capillaries were sparse and embedded in an abundant stroma. The majority of the nonvascular cells were either retinal pigment epithelial (RPE) cells or fibroblast-like cells. The RPE cells formed single or multiple layers on one side of the membranes. The stroma was composed mainly of collagen types I and IV and fibronectin, with small amounts of collagen types III, V, and VI. The absence of Bruch's membrane suggests that a splitting may occur between the RPE cells and Bruch's membrane with the new vessels growing into this cleft. A thickened layer of collagen type IV was often present under the RPE cells. The basement membranes of the newly formed capillaries were morphologically ill-defined, and contained substantial amounts of collagen type IV and fibronectin, but, unlike the basement membranes of normal capillaries, they lacked laminin or heparan sulfate proteoglycan.

CONCLUSION

These results on the ultrastructural components of the SRNVMs may be useful in clarifying the nature of the disciform process in ARMD.