What is the second layer from the choroidal side in Bruch's membrane?

• A. Outer Collagenous Layer
• B. Elastic Layer
• C. Inner Collagenous Layer
• D. Basement Membrane of the Choriocapillaris

Answer: (A)

Bruch's membrane is a five-layer sheet that lies between the choriocapillaris and the retinal pigment epithelium. Moving from the choroidal side toward the retina, the sequence is: basement membrane of the choriocapillaris, outer collagenous layer, elastic layer, inner collagenous layer, and basement membrane of the RPE. The second layer from the choroid is the Outer Collagenous Layer. This layer provides structural support with a dense network of collagen fibers, helping to anchor Bruch's membrane and contribute to its diffusion barrier between the choroid and the outer retina. The other layers in order are the choriocapillaris basement membrane (first), the elastic layer (third), the inner collagenous layer (fourth), and the RPE basement membrane (fifth).