Cystoid macular edema is primarily associated with which retinal layer?

• A. Outer Nuclear Layer
• B. Outer Plexiform Layer
• C. Inner Nuclear Layer
• D. Inner Limiting Membrane

Answer: (B)

Cystoid macular edema forms fluid-filled cystic spaces in the macula after leakage from retinal vessels. These spaces preferentially appear in the outer plexiform layer, where photoreceptor terminals connect with bipolar and horizontal cells. In the macula, especially the foveal Henle fiber layer, the tissue is arranged in a way that makes extracellular fluid collection into cysts most evident here. The inner nuclear layer contains cell bodies and is not the primary site for these cystic spaces, and the inner limiting membrane is simply the retina’s boundary rather than a layer where fluid accumulates. So the outer plexiform layer is the region most characteristically involved in CME.