Retinal histology

No teaching session this month – just as well, with the BAOP meeting coming up and arrangements to make!

There was some interest in a retinal photo I shared on Twitter yesterday, so I’m taking the opportunity to talk a little about retinal histology here.

High power view of photoreceptors (x40 objective)

The image I originally tweeted was of retina from an evisceration specimen. It shows some mild inner atrophy but has beautifully preserved photoreceptor inner segments (ie rods and cones).

Here are some more images from an enucleation specimen for comparison.

Medium power view of a normal(ish) macula

This is a medium power view of the macular region. The ganglion cell nuclei are multilayered, unlike in the periphery, and there is a dip where they disappear, indicating the fovea. The folding artefact is unfortunate, but it’s incredibly difficult to get a section from this region in a surgical specimen. I’ve examined around 800 globes and only identified the fovea histologically 3-4 times!

High power view of the fovea (x20 objective)

This is a closer view of the central area…

High power view of extrafoveal macula (x40 objective)

… and this is a high power view of the parafoveal macula. There is a multilayer of ganglion cell nuclei to the right of the image, and a high proportion of the photoreceptor inner segments to the left appear to be cone-shaped.

High power view of foveal photoreceptors (x40 objective)

In contrast, this is a high power image from the central part of the fovea. Although this is the region of the retina with the highest cone density, they are slender rather than cone-shaped (which leads me to wonder why cones elsewhere are cone-shaped, but that’s a question for some clever retinal biologist to answer!)

Whole globes, particularly those that contain tumour, present quite a challenge during microtomy. The sclera can be quite tough, the lens may be calcified, the tumour may be necrotic, and the retina has a tendency to fall off. I must thank the laboratory technical staff in the Department of Eye Pathology for their diligence in cutting such beautiful sections.

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