What is the fifth layer of Bruch's membrane when counting from the choroid to the retina?

• A. Basement Membrane of the Retinal Pigment Epithelium
• B. Basement Membrane of the Choriocapillaris
• C. Outer Collagenous Layer
• D. Elastic Layer

Answer: (A)

Bruch's membrane consists of five successive laminae when you move from the choroid toward the retina. The layer immediately adjacent to the choriocapillaris is its basement membrane, then the outer collagenous layer, followed by the elastic layer, then the inner collagenous layer. The innermost layer, closest to the retina, is the basement membrane of the retinal pigment epithelium. Therefore, the fifth layer from choroid to retina is the basement membrane of the retinal pigment epithelium. This arrangement supports nutrient/waste exchange between the choroid and photoreceptors and forms part of the outer blood-retina barrier; aging can cause thickening and drusen formation near the RPE basement membrane, impacting transport.