Between January 1, 1994, and December 31, 1996, 15 SST surgeons at 10 participating institutions and practices had voluntarily submitted to our laboratories surgically excised CNV tissue from patients enrolled in the SST pilot study for histopathologic examination. An informed consent form was signed by each patient prior to surgery. Patient age, sex, right or left eye, and presence or absence of ARMD were recorded by the submitting surgeon. No information was provided on whether the specimen came from group N, R, or B patients. The tissue was placed in 2.5% glutaraldehyde solution and processed for transmission electron microscopic examination. The specimens were postfixed with 0.1-mol/L cacodylate buffer and 1% osmium tetroxide solutions. Standard dehydration of the specimens was performed and the specimens were embedded in epoxy resin, sectioned, and stained with toluidine blue. Sections through the center of each specimen were evaluated for greatest linear CNV dimension and thickness, and for configuration of the CNV with regard to the neurosensory retina and retinal pigment epithelium (RPE). The diameter and thickness measurements were made with a reticule and standardized light microscope (Carl Zeiss Ltd, Oberkochen, Germany). Means of the greatest linear dimensions and thicknesses measured by the 2 independent observers (H.E.G. and W.R.G.) were recorded. The CNV configuration was listed as sub-RPE, between the neurosensory retina and RPE (subretinal), both sub-RPE and subretinal (combined), or unclassifiable.5 The orientation was accomplished by comparing the CNV with surrounding landmarks, such as photoreceptors, Bruch membrane, and basal laminar deposit (BLD). Semithin (0.1-µm) sections were cut and stained with uranyl acetate–lead citrate for transmission electron microscopy. A minimum of 20 micrographs per specimen was examined. Previously reported criteria6,7 were used for identification of specific cell types including RPE, vascular endothelium, fibrocytes, macrophages, myofibroblasts, glial cells, photoreceptors, lymphocytes, and extracellular components including collagen, fibrin, BLD, basal linear deposit, and fragments of Bruch membrane. The final diagnosis (CNV, fibrocellular tissue without CNV, hemorrhage, or other) was noted for each case.