**Core Concept**
The human eye is a complex sensory organ responsible for detecting light and color, with a unique structure and function that enables us to perceive the world around us. The eye's anatomy is composed of multiple layers and tissues, including the cornea, lens, retina, and optic nerve, which work together to transmit visual information to the brain.

**Why the Correct Answer is Right**
The correct answer is related to the structure and function of the human eye. The retina is a critical component of the eye, consisting of specialized cells called photoreceptors (rods and cones) that convert light into electrical signals. These signals are transmitted to the optic nerve, which carries them to the brain for interpretation. The retina is responsible for detecting light, color, and spatial information, and any damage to this area can lead to vision loss or blindness.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the iris is the colored part of the eye that controls the amount of light entering the eye through the pupil, but it is not responsible for detecting visual information.
**Option B:** Incorrect because the macula is a part of the retina responsible for central vision, but it is not the entire retina.
**Option C:** Incorrect because the optic nerve is responsible for transmitting visual information from the eye to the brain, but it is not the primary structure responsible for detecting light and color.

**Clinical Pearl / High-Yield Fact**
The retina is the only part of the central nervous system that is exposed to the external environment, making it vulnerable to damage from disease, injury, or age-related degeneration.

**Correct Answer:** D.