Which layer forms a blood barrier to the choroidal vessels?

Which layer forms a blood barrier to the choroidal vessels?

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

Answer: (D)

Between the choroid and the retina sits Bruch’s membrane, which acts as a diffusion barrier separating choroidal vessels from retinal tissues. Its layered basement-membrane structure regulates what substances can move from the highly permeable choroidal blood into the outer retina, helping keep the retinal environment stable. As Bruch’s membrane ages or thickens with deposits (drusen), its barrier function can weaken, contributing to retinal pathology. The other layers have different roles: the external limiting membrane is a cellular junction between photoreceptors and Müller cells, the inner limiting membrane lines the vitreous-retina boundary, and the RPE itself forms a cellular barrier, but the layer specifically forming the barrier between choroidal vessels and retina is Bruch’s membrane.

Between the choroid and the retina sits Bruch’s membrane, which acts as a diffusion barrier separating choroidal vessels from retinal tissues. Its layered basement-membrane structure regulates what substances can move from the highly permeable choroidal blood into the outer retina, helping keep the retinal environment stable. As Bruch’s membrane ages or thickens with deposits (drusen), its barrier function can weaken, contributing to retinal pathology. The other layers have different roles: the external limiting membrane is a cellular junction between photoreceptors and Müller cells, the inner limiting membrane lines the vitreous-retina boundary, and the RPE itself forms a cellular barrier, but the layer specifically forming the barrier between choroidal vessels and retina is Bruch’s membrane.