Vision and the Eye

Light

electromagnetic energy measured and described in wavelengths

hue

color; determined by the wavelength of light

intensity

amount of energy in light/ sound; determined by waves amplitude (ex. neon has higher than baby yellow)

Amplitude

the height of a wave

Cornea

dome shaped covering on front of the eye (where light enters) - transparent and PROTECTIVE

Pupil

black part; adjustable opening through which light passes (size controlled by iris)

Iris

ring of muscle tissue; colored portion'; controls pupils’ size

iris expand/ pupil contract

bright light

iris contract/ pupil expand

dark light

lens

transparent structure behind pupil which changes shape to focus on images (malfunction = need glasses)

Accommodation

process in which the lens changes structure to focus light on the retina

Vitreous Humor

thick transparent liquid in the eyeball which helps to give shape (clearness = lets light through)

Retina

light-sensitive inner back surface of the eye where vision happens (contains photo-receptors/ cones and rods)

rods

help see peripheral vision and black, gray, and white

cones

central vision that helps to see color (many at the fovea)

fovea

little dip in the retina where the lens focuses the light (central focus area)

Bipolar and Ganglion cells

help to TRANSDUCE light waves into neural impulses for optic nerve

Optic Nerve

Sends neural impulses from the eye to the brain

Blind Spot

where the optic nerve connects to the eye, no neurons here so cannot see!

Acuity

the sharpness of one’s vision (measure by vision chart)

Myopia (near)

easier to see close objects (light projected in front of fovea)

Hyperopia (far)

easier to see further objects (light projected behind fovea)

Astigmatism

blurring of image at retina (intense glare, typically at night) - caused by irregular shape of cornea/ lens

Retinopathy

damage to blood vessels of retina (blood cells leak into vitreous humor and cause floaters)

Glaucoma

fluid pressure builds up in eye/ eye swelling, causes damage to optic nerve (blurred vision and loss of peripheral vision)

Macular Degeneration

comes with age; dark spots in center of vision because there is less cell replication and degeneration of eye cells

Cataracts

with age; clouding of the lens (white in eye)

rods and cones - b and g cells - optic - opp thalamus - visual cortex

Visual info processing path

Parallel Processing

the brain’s natural mode of processing several things at once (see vision subdivisions, more than just color to see)

Vision subdivisions

movement, depth, form, and color

Hubel and Weisel

scientists who proved vision subdivisions

color vision

the colors one can see determined by amount of cones (humans have low/ limited while other animals can have more/ humans see rainbow only)

Young-Helmhoitz Trichromatic Theory

a theory of vision that the retina has THREE CONES which BLEND to let us see all other colors. These cones are red, green, and blue. If we cannot see a color, it is because it cannot be made from one of those three cones.

Color Deficiency/ Blindness

cones in the eye don’t function properly

Protanope

red cones don’t function right (hard to see red, looks brown)

Deuteranope

green cones don’t function right (green color is hard to see) - MOST COMMON!

Tritanope

Blue cones don’t work right (blue color is hard to see)

Afterimage

after viewing a color for a long period of time, then it is removed, one can see the COMPLIMENTARY COLOR! Think of the bee (black and white seems colorful)

Opponent Process Theory

theory of vision in which our ability to see color is controlled by 3 RECEPTOR complexes. These receptors are tuned ON / OFF, like a switch and only ONE can be activated at a time. Ex. red receptor suppresses green because of such different hue/ amplitude = not at same time.