Photoreceptors

Photoreceptors

1. LIGHT

   • light waves contain info about surfaces
   • light energy is reflected and absorbed
     • Proccess
       • light waves pass through the cornea and enter pupil
         • sensory receptors in retina (rods and cones) detect light waves
   • visable light is electromagnetic radiation

2. RETINAL GANGLION CELLS

   • 2 types
     • midget
       • input from CONES
     • parasol
       • input from RODS

3. CONES

   • 3 types
     • short
       • 'blue'
         • peak at 440nm
     • medium
       • 'green'
         • peak at 540nm
     • long
       • 'red'
         • peak at 570nm
   • fast response and recovery
   • High Acuity
   • Low Sensitivity
   • location
     • central retina
       • concentrated at the fovea
   • 6 million cones
   • function
     • detailed, central and chromatic vision

4. RODS

   • High Sensitivty
   • Low Acuity
   • slow response and recovery
   • 120 million rods
   • location
     • peripheral retina
       • increases towards the fovea but no rods at the fovea
   • one type
   • function
     • Peripheral and low light achromatic vision

5. COLOUR BLINDNESS

   • LOSE L/M differentation