RETINA, SEM. RETINA, SEM The retina is a membrane covering the eye´s interior, containing 3 types of cells which capture light: photoreceptor (rod and cone), bipolar, and ganglion. Photoreceptor cones are responsible for visual acuity and color vision. Cones are responsible for vision in low-light levels and for peripheral vision. Bipolars transmit the light signal from the cones to the ganglions, which then transmit the stimulus to the optic nerve. Here, rods, viewed under SEM. Magnification