ABSTRACT
The retina coats the back of the eye and is spherical, not at, making optical magnification constant at 3.5° of scan angle per millimeter. The retina is the neuronal front end of the visual system, the image sensor. Bipolar cells exhibit the first level of information processing in the visual system. Their response to light on the retina demonstrates “centre/surround” receptive fields, that is, a small dot on the retina elicits a response, while the area surrounding the spot elicits the opposite response. Many cues for depth are available to the visual system, including occlusion, vergence and accommodation of the eyes, expected size of objects, shape based on perspective, and shadow casting. Further evidence that successful development of the visual system depends on proper input comes from clinical experience with children who have cataracts at birth. Cataracts constitute a clouding of the lens, permitting light, but not images, to reach the retina.
