Vision

1. Vision By: Bethany, Iqra, Clint, Cameron, Nick

2. The Process • Light enters eye through the cornea • Then, it goes through the pupil which is surrounded by the iris • Fun Fact: When you’re around someone you like, your pupils dilate • Dark adaptation: pupils get bigger or smaller depending on surrounding • Behind pupil is the lens which focuses the light rays into an image on the retina • Lens first reverses the image

3. The Process Cont. Accommodation: lens will change its curvature to focus what you see

4. Nearsightedness: when the lens focuses objects in front of retina • Farsightedness: when the lens focuses objects behind the retina

5. How It Works • Retina: where transduction happens. • Thin, light sensitive layer of cells at the back of the eye • Eye gathers light, focuses it, converts it to neural signals, sends to brain • Transduction: eye converts light into neural signals the brain can process

6. Photoreceptors • These cells are called photoreceptors • Convert light energy into neural impulses • Two types: • rods: especially sensitive to dim light but not to colors. • cones: especially sensitive to colors but not to dim light • Cones are concentrated in the fovea where our vision is sharpest

7. Other Important Cells in Eyes • Bipolar cells: take impulses from rods & cones and takes it to ganglion cells • Ganglion cells: collects visual information • Axons make up the optic nerve which transports this information to brain • Blind spot: small area of retina where there are no photoreceptors • where the optic nerve leaves the eye • DEMO: Find YOUR Blind Spot!

8. Optic Chiasm Optic chiasm: where optic nerves from each eye meet

9. The Brain • Thalamus: sends the information to the visual cortex • Visual cortex: gets all information from optic nerve • Transforms neural impulses into visuals with color, form, movement • Makes 2D patterns 3D • Part of the occipital lobe which puts together the entire picture • Forebrain: makes connections, analyzes what you sees, spatial relationships

10. The Brain cont. • Parallel processing: brain divides each visual scene into subdimensions like color, movement, form and depth and works on each one at the same time • Brain creates color vision from wavelengths of light

11. Light Radiant light: visible energy released by an object (sun, lightbulb) Reflected light: visible energy reflected by object (grass, flowers)

12. Color Vision • Amplitude: intensity, brightness • Photoreceptors pick up wavelengths of light and change into neural impulses • Hue: color of object, created in visual cortex • Not a property of things • Psychological sensation created in the brain from the wavelengths of visible light • Saturation: how much color an object has • Acuity: how clear your vision is

13. How We Sense Color • Young-Helmhotlz trichromatic theory: colors are sensed by 3 different types of cones that see red, blue, and green wavelengths. Earliest stage of color vision • Opponent-process theory: cells in visual system process colors in complementary pairs (red or green and blue or yellow) • -Afterimages: sensations that linger after stimulus is removed because of retina fatigue. Usually are negative reversed)

16. Vision Disorders • Monochromats • complete color blindness. can’t distinguish any colors

17. Vision Disorders • Dichromats • Kind of color blindness where one of the three colors is missing