Human Visual System

The Brain and the Eye

		Three levels of membranes. Outer = Cornea: Transparent area, Sclera: Opaque	Choroid network of blood vessels heavily pigmented ciliary muscle: allows focusing of the lens iris: like a diapragm, controls quantity of light
		Lens made of layers of tissue 60 -70% water slightly yellow absorbs 8% of visible light
Retina: contains photorecptors, sensors that detect light contains rods and cones	Fovea Part of retina w/ central vision. Most cones are located here, w/ less rods.	rods 120 million, several per nerve ending achromatic vision = b/w, grayscale work well in low light conditions low spatial detail related to peripheral vision	cones 6-7 million fovea color fine detail work well in bright light 3 types, r, g, b

Layers in Retina

Distribution on Rods and Cones in EYE