Which retinal layer is referred to as the blood-barrier?

Which retinal layer is referred to as the blood-barrier?

• A. Bruch's membrane
• B. Retinal pigment epithelium
• C. Choroid
• D. Sclera

Answer: (A)

The barrier in the retina that protects neural tissue from blood-borne substances is formed by tight junctions that regulate diffusion between blood and retinal tissue, and there are two parts to it: an inner barrier at the retinal vessels and an outer barrier at the retinal pigment epithelium (RPE). The outer barrier is created by the tight junctions between RPE cells, preventing unregulated exchange from the choroidal blood supply into the retina. Bruch’s membrane sits between the RPE and the choroid as a thin extracellular layer that supports and regulates diffusion, but it is not the cellular barrier itself. So, the functional barrier that preserves retinal homeostasis is the RPE with its tight junctions (outer BRB), while Bruch’s membrane is a structural diffusion barrier, not the primary barrier mechanism.

The barrier in the retina that protects neural tissue from blood-borne substances is formed by tight junctions that regulate diffusion between blood and retinal tissue, and there are two parts to it: an inner barrier at the retinal vessels and an outer barrier at the retinal pigment epithelium (RPE). The outer barrier is created by the tight junctions between RPE cells, preventing unregulated exchange from the choroidal blood supply into the retina. Bruch’s membrane sits between the RPE and the choroid as a thin extracellular layer that supports and regulates diffusion, but it is not the cellular barrier itself. So, the functional barrier that preserves retinal homeostasis is the RPE with its tight junctions (outer BRB), while Bruch’s membrane is a structural diffusion barrier, not the primary barrier mechanism.