Which layer of the retina.

[KLPM]

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I have a question regarding looking at changes in the retina. I have seen a lot of pictures in books that say "this lesion is located in this layer."

e.g. location of haemorrhage, location of infiltrates.

Take this one for example:

The description says there is a "subretinal amelanotic choroidal mass". How do you know it is choroidal? As in it's in the choroid? Or am I misinterpreting? Maybe I am looking at the wrong thing? Is it that hazy area from the 7 to 9 o'clock position? I can see it is a deep lesion based on the fact vessels seem to be visible over it but I had be a bit hesitant to definitively say its location.

Any help with localising lesions to layers of the retina? I can sort of see how it works with haemorrhages but I use a mixture of guess work, shape and more guess work and colour.

 

[Dusn]

The easiest way is to get an OCT of it and see what layer the mass is on OCT. Or if you're as good as Don Gass you can figure it out with a hruby or contact lens.

I use an OCT personally.

 

[jsh1986]

I'd be very interested to learn more about this as well. During my department's retina conferences, the Fellows will comment that a picture suggests the infiltrate is choroidal, etc, which excludes certain things from the differential....I have no idea how they can tell.

I can differentiate epiretinal/subretinal from whether obscuration of the blood vessels is present but that's it.

Obviously OCT is one way, but surely there are characteristics that can give you a keen sense of localization?? Any tips, reviews, chapters, websites, etc. we can read?

 

[MstaKing10]

lesions deep to the retina will have overlying retinal structures such as blood vessels still visible. Lesions deep to the RPE will have a grey/brown appearance from the overlying RPE in additional to visible retinal structures (blood vessels). Thus, choroidal lesions have a brownish appearance with visible RPE and overlying retinal structures. Lesions superficial to the retina will obscure retinal structures.

If you are looking for lesions WITHIN the retina (ie. retinal layer), then this is a bit more difficult. In general, most fluid and lipid tends to accumulate in the outer plexiform layer (macular edema, "macular star" etc). Some conditions affect the internal limiting membrane (ILM) or nerve fiber layer (NFL) or photoreceptor layer exclusively. As mentioned before, OCT can be very useful for determining what layer is affected, though, cannot replace exam and clinical impression.

 

[KLPM]

I asked because when I first decided I actually want to learn some solid ophthalmology (since my medical school kind of skips it all) I came across the problem of localising which layer the retinal haemorrhages are.

I found that initially I had to memorise that flame haemorrhages are here, dot-blots are here etc. But when I actually thought about how the layers are arranged and what they look like it made more sense based on shape and colour of the lesions.

So in that example picture I posted is that sort of hazy brown-black lesion in the infer-temporal position the RPE being pushed up by an underlying choroidal mass?

 

[jsh1986]

Thanks this was helpful!