Which retinal layer forms a barrier to the retina's own blood vessels?

Which retinal layer forms a barrier to the retina's own blood vessels?

• A. External limiting membrane
• B. Bruch's membrane
• C. RPE
• D. Inner limiting membrane

Answer: (A)

Barriers inside the retina are built by specific layers that separate compartments and protect the delicate outer retina. The external limiting membrane is formed by adherens junctions between Müller glial cells and photoreceptor cells, creating a tight, continuous boundary between the inner retina and the outer retina. This makes it the gate that restricts movement from the vascular inner retina into the outer photoreceptor region, effectively acting as a barrier to the retina’s own blood vessels reaching the outer layers. The other options describe barriers at different interfaces: Bruch’s membrane lies between the retina (via the RPE) and the choroid; the RPE forms the outer blood-retina barrier between the retina and choroidal circulation; and the inner limiting membrane is the boundary with the vitreous, not a barrier to the retina’s vascular network.

Barriers inside the retina are built by specific layers that separate compartments and protect the delicate outer retina. The external limiting membrane is formed by adherens junctions between Müller glial cells and photoreceptor cells, creating a tight, continuous boundary between the inner retina and the outer retina.

This makes it the gate that restricts movement from the vascular inner retina into the outer photoreceptor region, effectively acting as a barrier to the retina’s own blood vessels reaching the outer layers. The other options describe barriers at different interfaces: Bruch’s membrane lies between the retina (via the RPE) and the choroid; the RPE forms the outer blood-retina barrier between the retina and choroidal circulation; and the inner limiting membrane is the boundary with the vitreous, not a barrier to the retina’s vascular network.