Enucleation specimen
The patient is an elderly male. The reason for surgery is a choroidal melanoma, but I’m not going to show that in this post: there’s something else of note.
This low power image shows the anterior segment (cornea, iris, ciliary body and lens). The feature of interest is that instead of having a single oval(ish)-shaped lens just behind the pupil, we have two ovalish structures that look like mini-lenses, one behind each iris leaflet.
In the annotated image, I’ve marked the anatomical structures plus the oddities. CB = ciliary body.
A medium power view shows us one iris leaflet and a few ciliary processes. The oval structure has the appearance of lens material, and it is bounded by a discontinuous layer of basement membrane (ie lens capsule). So we have a piece of lens with capsule, just behind the iris.
In the annotated image, I’ve marked the anterior (thicker) lens capsule in green and the posterior (thinner) capsule in yellow. CP = ciliary processes. Those tiny fragments marked with “z” are pieces of lens zonules.
This is a high power of the lens material. Lens fibres are usually (as their name suggests) long strands. But here, they are rounded blobs that we might describe as balloon-shaped. The cells closer to the capsule have nuclei, whereas those further in have lost their nuclei. This reflects lens fibres arising from lens epithelial cells, which are located just under the capsule. Fibres are produced throughout life, and the lens becomes increasingly compacted with age as more fibres accumulate. (I point out, this is my very simplistic view and probably not strictly accurate).
In the annotated image, I’ve outlined a few of the “balloon cells” in green. Note the amorphous cytoplasm.
And here’s a PAS-stained image, highlighting the lens capsule. Note how thick the anterior capsule is compared to the posterior capsule. The anterior lens capsule is one of the thickest basement membranes in the human body: although it is surpassed by Descemet’s membrane.
So, what’s going on here? This is the histological appearance of a Soemmering (sometimes spelled “Soemmerring,” I haven’t ascertained which is correct) ring cataract. During cataract surgery, the “bag” (lens capsule) is opened anteriorly, and the lens removed. It doesn’t come out as a single piece, and residual cortex must be aspirated – essentially, hoovering up the pieces. The thin posterior capsule is at risk of rupture (an unwanted complication), and so there is a balance between aspirating every last piece of cortex and potentially rupturing the capsule. Often, some cortex is left behind. Over time, this can accumulate around the periphery of the bag (capsule) while the IOL (intraocular lens implant) occupies the centre of the bag. Ring cataracts are often asymptomatic because they don’t obscure the visual axis.
Here’s another case. Again, we see an anterior segment with two pieces of lens lying behind the iris leaflets. In this case, we can also make out a portion of intraocular lens. IOLs are clear and synthetic, and they don’t always appear on the section. In this case, it has folded over during microtomy.
The annotated image outlines the IOL.
Selected references
The cause and consequence of fiber cell compaction in the vertebrate lens by Bassnetta and Costellob (2017). This is a comprehensive review of lens physiology and refractive index. The first 3 sections give a nice overview of lens development although after that it became more technical than I was looking for.
Soemmering’s ring by Bhattacharjee and Deshmukh (2017) has a nice clinical image
And here are a couple of articles with historical context
Soemmering’s Ring and its Dislocations by Guha (1951)
Soemmerring’s ring—a review and three illustrative cases by Stokoe (1957)
eyepathlondon 