Vision

Structure of the Eye

We only use light energy to see.

Wavelength The distance from the peak of one light wave to the peak of the next. The distance determines the hue (color) of the light we perceive.

Intensity The amount of energy in a light wave. Determined by the height of the wave. The higher the wave the more intense the light is.

Vision – front of eyeball – phase 1  Pupil- adjustable opening in the center of the eye  Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening  Lens- transparent structure behind pupil that changes shape to focus images on the retina

Nearsighted Vision

Farsighted Vision

Inner eye – phase 2  Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina  Retina- the light-sensitive inner surface of the eye  receptor rods and cones  layers of neurons that begin the processing of visual information

The Retina

Rods and Cones – 125 million rods to 7 million cones per eye! Rods – sensitive to variations in light, helps us adjust to dark. Full adjustment = 30 minutes Cones – sensitive to color, bright light. Full adjustment = 5 minutes

Retina’s Reaction to Light  Optic nerve- nerve that carries neural impulses from the eye to the brain  Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there  Fovea- central point in the retina, around which the eye’s cones cluster. Greatest visual acuity

Blind spot

Processing from retina to the brain – phase 3 Bipolar Cells – preliminary sensory reception area. Raw data Ganglion cells – neurons that are photoreceptive – processes fine details from cones From retina cells go to optic nerve and then optic chiasm

Color Processing  Trichromatic (three color) Theory  Young and Helmholtz  three different retinal color receptors  red  green  blue

Color-Deficient Vision  People who suffer red-green blindness have trouble perceiving the number within the design

Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision “ON”“OFF” red green green red blue yellow yellow blue black white white black

Opponent Process Theory – Afterimage effect

Feature Detection The concept that specific nerve cells in the brain respond to specific features of the stimulus, such as shape, angle, or movement.

Parallel Processing The processing of several aspects of a problem simultaneously. Color MotionForm Depth