Why is the retina considered inverted?

• A. Photoreceptors are at the front and initiate signals
• B. The phototransduction signal is reversed in the brain
• C. Photoreceptors are in the back but initiate the phototransduction signal
• D. The retina has an extra protective layer that delays signals

Answer: (C)

The retina is described as inverted because the light must pass through several neural layers before reaching the photoreceptors, which sit behind them. The rods and cones are the light-detecting cells, and they initiate phototransduction the moment they absorb photons. Once triggered, the signal is carried forward through the retinal circuitry—bipolar and ganglion cells—toward the optic nerve. Although the image formed on the retina is flipped due to the eye’s optics, the brain ultimately interprets it as upright. The special case of the fovea, where inner retinal layers are displaced to minimize light scattering and maximize acuity, doesn’t change the fundamental arrangement that photoreceptors are located toward the back of the retinal structure.