Visual System

Structure

The human visual system comprises a complex collection of structures that transforms light into a rich palette of visual information that one experiences as the physical environment. The most recognizable element of the system is the eye, the peripheral organ of vision. Light rays are refracted by the cornea and projected through the pupil to the photoreceptive cells (rods and cones) of the retina at the back of the eye where the transformation of light energy into chemical messages begins. The rods are found with relatively greater frequency in the periphery of the retina and are better adapted to low-intensity light, such as night vision. The cones are more concentrated in the macula, particularly in the center of the macula or fovea, are better adapted to the perception of color and the sharper point-to-point vision necessary for fine discriminations (foveal vision). While other cells (horizontal cells) serve as interneurons, it is basically the rods and cones that...