Which layer forms a blood barrier to the retina blood vessels?

Which layer forms a blood barrier to the retina blood vessels?

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

Answer: (A)

The outer blood-retina barrier is formed by tight junctions in the retinal pigment epithelium (RPE). These junctions between RPE cells prevent diffusion from the choroidal blood supply into the retina, helping maintain the retinal environment. The other structures don’t serve this barrier role: the external limiting membrane is a network of junctions between photoreceptors and Müller cells, not a barrier to blood flow; Bruch's membrane sits between the RPE and the choroid and acts as a diffusion barrier for substances moving between those layers but isn’t the retinal blood barrier itself; the inner limiting membrane marks the boundary at the inner retina to the vitreous and isn’t involved in blocking vascular diffusion.

The outer blood-retina barrier is formed by tight junctions in the retinal pigment epithelium (RPE). These junctions between RPE cells prevent diffusion from the choroidal blood supply into the retina, helping maintain the retinal environment. The other structures don’t serve this barrier role: the external limiting membrane is a network of junctions between photoreceptors and Müller cells, not a barrier to blood flow; Bruch's membrane sits between the RPE and the choroid and acts as a diffusion barrier for substances moving between those layers but isn’t the retinal blood barrier itself; the inner limiting membrane marks the boundary at the inner retina to the vitreous and isn’t involved in blocking vascular diffusion.