1. Presented By: Jenna, Jeff, and Olivia
Vision
Presented By: Jenna, Jeff, and Olivia

2. My head is spinning just from reading these!
Essential Questions
What parts of the visual system create and process images?
What are some theories related to color vision and what do they state?
Name some common visual disorders and what causes them.
My head is spinning just from reading these!

3. Structure of the Eye

4. Structure
Iris: Colored part of the eye; contracts and expands retina in response to light and protects it
Pupil: Hole in the center of the iris where light passes through
Cornea: Clear, dome-shaped surface that covers eye; first (and most powerful) lens
Lens: keeps images in focus (adjustable for close work/distance); inverts images and sends to brain

5. Retina: film over the eye; converts light into electrical signals to send to the brain
Blind Spot: location where the optic nerve exits the eye; anything that falls in this area is not seen
Bipolar cells: cells in the retina that connect receptors to ganglion cells
Ganglion cells: axons of these cells form the optic nerve; located in the retina
Fovea: area of the retina that controls central vision

6. Structures that help with vision, but aren’t totally located in the eye
Optic Chiasm: where the optic nerve fibers from each eye meet
Optic Nerve: group of neurons that transfer visual information from the retina to the brain
Visual Cortex: area in the brain that processes vision, and combines it in order to create an image
Forebrain: receives and processes visual information (contains the visual cortex)
Occipital Lobe: located in the forebrain; contains the visual cortex
Thalamus: processes visions; information from the optic nerves is relayed here, and then to the cerebral cortex

7. Photoreceptors
Light sensitive cells (neurons) in the retina that convert light energy to neural impulses
Furthest that light travels in the visual system
Two types:
Rods: most sensitive to light, but not to color; 120 million
Cones: provide eye’s color sensitivity; 6-7 million
Visual Phototransduction: process through which photoreceptors convert light into electrical signals in the rods and cones of the retina

8. Visual Processing Images enter through lens and are inverted
info on viewer’s left is taken in on right side of the eye
Eye sends info to optic chiasmus
info on left side sent to be right cerebral hemisphere, processed by right occipital lobe
Neurons of cerebral cortex pass their separate analyses of the image into parietal lobe and temporal lobe
assembled and integrated w/ emotions, memories into meaningfulness

10. Eye Disorders
Nearsighted: inability to see objects that are far away; eyes have difficulty refracting light
Farsighted: inability to see objects that are nearby; eye ball is either too short or lens cannot become round
Blindness: inability to see
Cataracts: clouding of the lens
Glaucoma: increased pressure within the eye

11. Some Functions of the Eye
Accommodation: when eye muscles change to focus on something close or far away
Normally in lens, pupil size, and movement of eyes in opposite directions to keep binocular vision
Dark Adaptation: chemical and physical changes undergone in eye to make it possible to see in relative darkness
Includes dilating pupil, and increasing activity in rods

12. More Functions of the Eye
Parallel Processing: ability of brain to simultaneously process incoming messages of different quality (multitasking for your eyes)
Important for vision because brain first divides vision into color, motion, shape, depth then synthesizes it
Acuity: clearness of vision
Usually depends on focused retina, and how well brain interprets images

13. What is color?
Color/ Hue: sensation created in the brain from wavelengths of light and visual information gathered from the eyes
Color is a sensation, so it does not exist outside of the brain
Only exists in the individual mind
Created when light waves are translated by photoreceptors into neural impulses, and are transferred to specialized areas of the brain to be processed

14. Electromagnetic Spectrum
The range of electromagnetic energy
Includes:
Radio waves
Microwaves
Infrared
Visible Light
Ultraviolet
X-Rays
Gamma Rays

15. More information about the Electromagnetic Spectrum
Classifications in the electromagnetic spectrum depend on the wavelength of a wave as well as its amplitude
Wavelength: length of a light wave
Amplitude: strength/ intensity of something (usually a stimulus)
Peak/ Crest: Top of the wave
Trough: bottom of the wave
Frequency: Speed of the wave
The only section of the electromagnetic spectrum that is visible to us is the small, and properly named, section called “Visible Light”

16. Visible Spectrum
Small section of the Electromagnetic Spectrum that our eyes are sensitive to
Light waves with different wavelengths within the Visible Spectrum, create different colors
Waves come from Radiant and/or Reflected Light
Radiant light: visible energy emitted by something
Reflected light: energy reflected by objects
The eye extracts information from the wavelength of a light ray in order for the brain to process color

17. Visible Spectrum
Visual experiences of color, form, position, and depth, are all based on processing one stream of sensory information in multiple parts of the visual cortex
Since color only exists within the brain, perception of a color can vary in saturation and brightness
Saturation: purity of a color
Brightness: psychological sensation that is based on a light wave’s intensity

18. Theories on viewing colors
Trichromatic theory: idea that colors are sensed by three different types of cones sensitive to light in red, blue, and green wavelengths
explains earliest stages of color sensation
also called Young-Helmholtz theory

19. Another theory
Opponent-process theory: idea that cells in visual system process colors in complementary pairs, such as red and green or yellow and blue
explains color sensation from bipolar cells onward in visual system

20. Afterimages Sensations that linger after stimulus is removed
negative afterimages appear in reversed colors

21. Monocular Cues Depth perceived in each individual eye
Types: relative size, interposition, relative clarity, texture gradient, relative height, relative motion, light, shadow

22. Binocular Cues Depth perceived using both eyes
Types: Retinal disparity, Convergence
Retinal disparity: the difference between the visual images that each eye perceives because of the different angles viewed
Convergence: coordinated movement of eyes inward to focus on objects close to us

23. Optical Illusions (Fun ways to mess with your eyes!)

25. THE END