Fovea: Central Retina's High-Density Photoreceptor Region

Steps:

• Identify light receptors as photoreceptors (rods and cones) in the retina.
• Recall eye anatomy: retina lines the back, with varying receptor density.
• Note central vision requires sharp focus, demanding more receptors.
• Locate fovea as retina's center for detailed vision.

Why D is correct:

• The fovea is a small retinal pit packed with cones (over 200,000 per mm²), maximizing light detection for acuity, per retinal anatomy.

Why the others are wrong:

• A. Cornea: Transparent front layer for light refraction, no photoreceptors.
• B. Optic nerve: Bundle of axons transmitting signals, lacks receptors.
• C. Iris: Colored muscle controlling pupil size, no light receptors.

Final answer: D