Vision begins in the retina.

Vision begins in the retina.

• A. Cornea
• B. Lens
• C. Optic nerve
• D. Retina

Answer: (D)

Light must be detected by photoreceptors in the retina to begin vision. The retina, a light-sensitive layer at the back of the eye, contains rods and cones that transduce photons into electrical signals. This phototransduction changes the photoreceptors’ membrane potential and starts the signaling cascade through bipolar and then ganglion cells. The signals are carried by the retinal ganglion cell axons, which form the optic nerve and route information to the brain for further processing. The cornea and lens only focus light, and the optic nerve transmits signals rather than initiating their sensory transduction. So the first step in vision occurs in the retina.

Light must be detected by photoreceptors in the retina to begin vision. The retina, a light-sensitive layer at the back of the eye, contains rods and cones that transduce photons into electrical signals. This phototransduction changes the photoreceptors’ membrane potential and starts the signaling cascade through bipolar and then ganglion cells. The signals are carried by the retinal ganglion cell axons, which form the optic nerve and route information to the brain for further processing. The cornea and lens only focus light, and the optic nerve transmits signals rather than initiating their sensory transduction. So the first step in vision occurs in the retina.