NBEO Ocular Disease Part 1 Practice Test

The key idea here is recognizing endothelial dysfunction as the basis of the disease. Fuchs dystrophy is an endothelial dystrophy, meaning it starts in the innermost layer of the cornea where the endothelial cells govern fluid balance. In Fuchs, these endothelial cells progressively die off and characteristic guttae form on Descemet’s membrane. As the endothelium fails to pump out fluid effectively, the cornea swells (edema), especially after waking, leading to blurry vision and glare. It’s a slowly progressive, usually bilateral condition that tends to present in middle to older age, making it the most common endothelial dystrophy by far.

Keratoconus, by contrast, is a stromal thinning and bulging of the cornea (an anterior surface issue rather than endothelial), not a dystrophy of the endothelium. Pterygium is a surface conjunctival growth that can affect vision but does not involve endothelial cell degeneration. Descemet’s membrane detachment is an acquired mechanical problem where Descemet’s membrane separates from the stroma, often after surgery or trauma, and is not a dystrophy of the endothelial cells.