In this chapter, the anatomy, optics, physiology, and psychophysics of the human visual system will be summarized. The visual sense depends on the conversion of electromagnetic energy within a narrow range of wavelengths (from about 300 nm to 700 nm) into electrical energy within the retina. This is followed by a series of processing stages resulting in an output from the retina to several different parts of the midbrain and thalamus. Subsequently, signals are processed and may lead to conscious interpretation utilizing many regions of the cerebral hemispheres. Perhaps 50% of human visual cortex is visually sensitive.