Fig. 2.

Histological macular appearance in another eye affected by diabetic retinopathy (an 83 yo subject). Tissue was fixed in 4% paraformaldehyde solution within 7 hours of death. An 8 mm diameter punch including neural retina, choroid and sclera was collected, centered on the fovea centralis. The punch underwent cryopreservation through a series of sucrose solutions followed by embedding in optimal cutting temperature compound (Ted Pella) and freezing in liquid nitrogen. Cryostat sections were collected at a thickness of 7 μm onto Superfrost plus slides (Fisher) and were stained with hematoxylin/eosin stain.

Multiple cysts are present within the outer plexiform layer, as observed in classical DME. However, below these cysts are pseudocysts between the photoreceptors and the RPE monolayer, which is artifactually noncontinuous. Wherever the pseudocyst is present, the outer nuclear layer is compressed and degenerated to as little as one nucleus thick, suggesting compression on and toxicity to the photoreceptor cells. The ONL is present with inner and outer segments in the center where the pseudocysts are not present.