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

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

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

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

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

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

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!

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

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

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

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

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

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 ofretina fatigue. Usually are negative reversed)

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

Vision Disorders Dichromats –Kind of color blindness where one of the three colors is missing