Fig 5. Histology of the occlusion site.

Veins were occluded at d0. Two days later, eyes were prepared for serial paraffin sections that were stained with HE. Typical sections from three RVO eyes and three control eyes are shown. A1—A4: Sections at different positions of a single laser site. The RPE is slightly affected and Bruch’s membrane is intact. The inner limiting membrane is detached by a large inner retinal serous exsudation, and the INL is also affected by a serous exsudation. A1 is from the distal part of the laser site with the vein containing erythrocytes. A2 shows a fold (invagination) within the outer retina and a vein that contains a fibrous plug. A3 is from the center of the laser site showing a large retinal invagination and a bleeding vein containing a fibrous plug. A4 is from the proximal part of the laser site showing the retinal fold within the RPE and a decreased vein. The whole series of sections is shown in the supplemental S1 Fig. B1—B4: Sections at different positions of another single laser site. The inner limiting membrane is detached by a large inner retinal serous exsudation, and the INL is also affected by a serous exsudation. RPE and Bruch’s membrane are perforated as is seen in B3. B1 shows the distal part of the laser site with a fold of photoreceptor outer segments within the RPE and a vein containing a fibrous plug. B2 shows a fold within the outer retina. B3 is from the central part of the laser site showing a retinal fold and fused material of photoreceptors, RPE, and choroid. B4 shows the proximal vein that is diminished and a lateral part of the laser site with a fold of outer segments of the photoreceptors. The retina shows unequal thickness. The whole series of sections is shown in the supplemental S2 Fig. C1—C3: Sections from control laser sites without vein occlusion. The morphology of the laser sites is principally equal to RVO laser sites. C1 shows a fold of the outer retina of a laser site with intact Bruch’s membrane. The choroid is affected as shown by its reduced thickness at the center of the laser site. C2 and C3 are sections from a laser site with disrupted RPE and choroid. The choroid shows a reduced thickness, and even the sclera is affected. The material of the outer retinal fold is partially fused. C4 is a section from an intact retina for comparison. ILM: inner limiting membrane; INL: inner nuclear layer; ONL: outer nuclear layer; POS: photoreceptor outer segments; RGC: retinal ganglion cells.