Which three types of retinal cells are found in the middle layers as light passes through the retina?

• A. Bipolar, Horizontal, Amacrine
• B. Photoreceptors
• C. Ganglion cells
• D. Retinal pigmented epithelium

Answer: (A)

Light must pass through several retinal layers before signals reach the output cells, and the middle layers host the neurons that do the key processing on the way. Bipolar cells act as the main relay from photoreceptors to the next stage, conveying the detected light information toward ganglion cells. Horizontal cells provide lateral connections across neighboring photoreceptors, shaping contrast and receptive fields to refine the signal. Amacrine cells perform further modulation in the inner part of the retina, influencing how signals from bipolar cells are integrated before reaching ganglion cells.

Photoreceptors live in the outer part of the retina and detect light, so they aren’t part of the middle layers. The retinal pigmented epithelium sits outside the neural retina and supports photoreceptors, not involved in the middle-layer processing. Ganglion cells are in the innermost layer, receiving the processed signals from bipolar and amacrine cells, not in the middle. Thus, the three cell types found in the middle layers are bipolar, horizontal, and amacrine.