What is the approximate peak density of cones in the foveola?

• A. 100,000 cones/mm^2
• B. 200,000 cones/mm^2
• C. 300,000 cones/mm^2
• D. 400,000 cones/mm^2

Answer: (B)

The question tests how densely packed cones are in the foveola, the spot of highest visual acuity in the retina. In the foveola, cones are packed extremely tightly to sample the image at a very fine spatial scale. The approximate peak density is about 200,000 cones per square millimeter. This dense packing supports sharp, detailed central vision because each cone contributes to the image with minimal averaging, especially since the fovea has a near one-to-one or small convergences with midget ganglion cells. The foveola is also rod-free and structurally optimized (a shallow pit to reduce light scattering), all of which together maximize acuity. Outside the fovea, cone density falls off, which is why peripheral vision has lower spatial resolution.