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. 2021 Mar 17;62(3):25. doi: 10.1167/iovs.62.3.25

Figure 6.

Figure 6.

Histologic changes after half-dose half-fluence vPDT (groups 1, 3, and 4). (A) Light microscopy section with toluidine blue stain at magnification × 20 demonstrating the inner retina and choroid close to the laser spot. Pigment-laden macrophages were observed (indicated with solid black arrows). A monolayer of regenerated RPE cells with few melanin granules was seen. These cells were flatter in shape and hypopigmented because of the damage induced by vPDT (in contrast to the RPE cells in Figure 3A after administration of systemic adrenaline). A few pyknotic nuclei were seen in the ONL (indicated with interrupted black arrows). (B) Corresponding electron microscopy section at magnification × 890 demonstrating a monolayer of depigmented regenerating RPE cells after vPDT and pigment-laden macrophages (indicated with solid black arrows). (C) Composite image of light microscopy section with toluidine blue stain at magnification × 40 of the central part of the vPDT laser spot. The outer nuclear layer was disrupted. Most of the photoreceptor cells were lost. Few residual cone cells with the inner segments were seen at the foveal center. Pigment-laden macrophages were attached to the retina (indicated with solid black arrows). The RPE layer was composed by flat cells with few melanin granules. The lumens of the choriocapillaris were narrow (indicated with interrupted black arrow), and choroidal venules had narrow lumens (indicated with black asterisks). (D) Corresponding electron microscopy section at magnification × 1900 demonstrating a subretinal pigment-laden macrophage. (E) Light microscopy section at magnification × 20 as negative control for vascular endothelial growth factor (VEGF) staining of central area of vPDT. (F) Light microscopy section with VEGF antibody stain at magnification × 20 demonstrating marked VEGF staining in the choroidal stroma. There was positive staining of the subretinal macrophages (indicated with solid black arrows). There were also many round-shaped and spindle-shaped cells in the choroidal stroma compared with the control specimen. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; OLM, outer limiting membrane; PRL, photoreceptor layer; CC, choriocapillaris; PLM, pigment-laden macrophage.