How does Bruch's membrane appear in an OCT scan?

• A. A thick elevated ridge at the vitreous boundary
• B. A dark band anterior to the RPE
• C. A thin, highly reflective line just posterior to the RPE
• D. A bright circular ring at the optic nerve

Answer: (C)

The key idea is how OCT shows retinal boundaries by reflectivity. Bruch's membrane sits between the RPE and the choroid, and on OCT it appears as a very thin, highly reflective line just posterior to the RPE. The bright line marks the boundary between the RPE and the choroid, so you’ll see a distinct, slim reflective line immediately behind the RPE.

Other options describe structures not Bruch's membrane: a thick elevated ridge at the vitreous boundary would relate to the vitreoretinal interface, a dark band in front of the RPE isn’t the Bruch’s membrane line, and a bright circular ring at the optic nerve relates to the optic nerve head region, not Bruch's membrane.