VISION

LIGHT

Electromagnetic energy Electromagnetic energy described in wavelengthsdescribed in wavelengths

Main colors of the spectrum:Main colors of the spectrum:RROOYYGGBBIIVV

                                                                

PUPIL

Determines amount of light let Determines amount of light let into eyeinto eye

                                                                

LENS

Focuses light rays onto the Focuses light rays onto the retina. retina.

Adjusts to the distance of objects Adjusts to the distance of objects by changing its thickness (squint)by changing its thickness (squint)

                                                                

RETINA Nerve layer that lines the back of the Nerve layer that lines the back of the

eye.eye. Contains rods, cones, & neurons Contains rods, cones, & neurons

(photoreceptors) that process visual (photoreceptors) that process visual stimulistimuli

Macula -- a small area in the retina Macula -- a small area in the retina - allows us to see fine - allows us to see fine

details clearlydetails clearly..

BLIND SPOT

Part of retina that contains no Part of retina that contains no photoreceptorsphotoreceptors

Located where Optic Nerve Located where Optic Nerve leaves the eyeleaves the eye

CORNEA

The clear front window of the eye. The clear front window of the eye. The cornea transmits and focuses The cornea transmits and focuses light into the eyelight into the eye. .

IRIS

The colored part of the eye. The The colored part of the eye. The iris helps regulate the amount of iris helps regulate the amount of light that enters the eye. light that enters the eye.

Vitreous -- the clear, jelly-like Vitreous -- the clear, jelly-like substance that fills the middle of the substance that fills the middle of the eye. eye.

OPTIC NERVE

Connects the eye to the brainConnects the eye to the brain

Carries the impulses formed by Carries the impulses formed by the retina to the brain, which the retina to the brain, which interprets them as images.interprets them as images.

RODS & CONES

Rods -Rods - - night vision; black & white, - night vision; black & white, light & darklight & dark95% of photoreceptors are rods95% of photoreceptors are rodsRods - long + narrowRods - long + narrow

RODS & CONES

Cones Cones Responsible for color visionResponsible for color visionAbout 5% of photoreceptorsAbout 5% of photoreceptorsRods - thick + taperedRods - thick + tapered3 Types:3 Types:

Red, Green/Yellow, Blue/VioletRed, Green/Yellow, Blue/Violet

COLOR BLINDNESS

Partially or totally unable to Partially or totally unable to distinguish colordistinguish color

                            

                            

                            

COLOR BLINDNESS

People who see all colors called People who see all colors called trichromatstrichromats (from the Greek (from the Greek term meaning “three colors”term meaning “three colors”

Smaller number of people Smaller number of people see only see only two colorstwo colors = = dichromatsdichromats

COLOR BLINDNESS

MonchromatsMonchromats -- -- See the world in See the world in only black and white. Occurs in only black and white. Occurs in about 1 in every 100,000 men.about 1 in every 100,000 men.

COLOR VISION Color CircleColor Circle – light spectrum is bent – light spectrum is bent

in a circle – colors across from one in a circle – colors across from one another are complimentary another are complimentary

COLOR VISION

Afterimage Afterimage = = visual sensation that occurs visual sensation that occurs

after original stimulus has been after original stimulus has been removedremoved

Is seen in the complimentary Is seen in the complimentary colorcolor

-Stare at the eye of the red parrot while you count slowly to 20, then look immediately at one spot in the empty bird cage. The faint, ghostly image of the blue green bird will appear in the cage.

-Try the same thing with the green cardinal. A faint magenta bird will appear in the cage.

-Stare at the eye of the red parrot while you count slowly to 20, then look immediately at one spot in the empty bird cage. The faint, ghostly image of the blue green bird will appear in the cage.

-Try the same thing with the green cardinal. A faint magenta bird will appear in the cage.

ADAPTATION Dark adaptation = rods & cones Dark adaptation = rods & cones

become more sensitive to lightbecome more sensitive to light (entering a dark room) (entering a dark room)

Light adaptation = r & c become Light adaptation = r & c become less sensitive (leaving dark room less sensitive (leaving dark room into light)into light)

VISUAL ACUITY

Sharpness of visionSharpness of vision Determined by the ability to see Determined by the ability to see

visual detailsvisual details

Corrective Lenses