65. The Middle Limiting Membrane
A 68-year-old man presents with sudden visual loss.
In this OCT image there is thickening and hyperreflectivity of the inner retinal layer. The outer retinal layer is hyporeflective because there is shadowing as light is having difficulty moving through the inner layers. There is a sharp demarcation between the inner and outer retinal layers, which is called the “middle limiting” membrane. This is an artificial membrane, as opposed to the internal and external limiting membranes. There is also increased relative reflectivity in the fovea.
This is because the patient has a central retinal artery occlusion (CRAO), and this central hyperreflective area is compatible with a cherry-red spot.
If you see a sharp demarcation between inner hyperreflectivity and outer shadowing, or a “middle” limiting membrane, a CRAO needs to be ruled out.
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