Structure of eyes and retina Schematic diagram of

Structure of eyes and retina Schematic diagram of the vertebrate eye Rods are most densely packed about 3 mm away from fovea; Cones are located largely in fovea, where they are 150000 mm-2 Section of retina

Two types of vision mode 1. Scotopic vision: rods 2. Photopic vision: cones In a normal eye, about 6 million cones and about 120 million rods. The characterization of rods and cones the structures of rod and cone Rods can respond for low intensity light— 10 -9 lx, about 100 times more sensitive than cones but have long response time, about 100 ms; Cones have less sensitive than rods and shorter response time, about 20 ms. Rod and cone photoreceptors: Molecular basis of the difference in their physiology Satoru Kawamura , Shuji Tachibanaki，Comparative Biochemistry and Physiology, Part A 150 (2008) 369– 377

Response curves of rods and cones Relative intensity of absorbance There are three types of cones, about 64% of the cones are red sensitive (L-type ones), about 32% are green sensitive (M-type ones), and about 2% are blue sensitive (S-type ones). Human spectral sensitivity curves. (1) scotopic sensitivity; (2) photopic sensitibity; Circles: Absorption spectrum of human rod pigment. The Senses, Horace Basil Barlow, J. D. Mollon Wavelenth/nm Simplified human cone response curves, based on Dicklyon's PNG version, itself based on data from Stockman, Mac. Leod & Johnson (1993) Journal of the Optical Society of America A, 10, 2491 -2521 d

Color blindness There are three types of inherited or congenital color vision deficiencies: 1. monochromacy: monochromacy occurs when two or all three of the cone pigments are missing and color and lightness vision is reduced to one dimension. 2. dichromacy: a moderately severe color vision defect in which one of the three basic color mechanisms is absent or not functioning. ] 3. anomalous trichromacy: a common type of inherited color vision deficiency, occurring when one of the three cone pigments is altered in its spectral sensitivity.

Dichromacy The colors of the rainbow as viewed by a person with no color vision deficiencies. The colors of the rainbow as viewed by a person with deuteranopia. http: //en. wikipedia. org/wiki/Color_blindness The colors of the rainbow as viewed by a person with protanopia The colors of the rainbow as viewed by a person with tritanopia.

Night Blindness 1. A disorder in which the rod cells in the retina gradually lose their ability to respond to the light 2. Deficiency of retinol, or vitamin A, found in fish oils, liver and dairy products http: //en. wikipedia. org/wiki/Carrots http: //en. wikipedia. org/wiki/Second_World_War

Find a black dot http: //www. visionrx. com/library/optical_illusion 1. asp

Blowing in the Wind Are the long diagonal lines bending? http: //www. visionrx. com/library/optical_illusion 1. asp

A snapshot of the "color dove illusion"