Transcript Vision

Vision
• Pupil- adjustable opening in the center of
the eye
• Iris- a ring of muscle the 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
Vision
Vision
• Accommodation
– change in shape of lens
– focus near objects
• Retina
–
–
–
–
–
inner surface of eye
light sensitive
contains rods and cones
layers of neurons
beginning of visual information processing
Vision
• Acuity- the sharpness of vision
• Nearsightedness
– nearby objects seen more clearly
– lens focuses image of distant objects in front
of retina
• Farsightedness
– faraway objects seen more clearly
– lens focuses near objects behind retina
Retina’s Reaction
to
Light- Receptors
• Cones
– near center of retina (fovea)
– fine detail and color vision
– daylight or well-lit conditions
• Rods
– peripheral retina
– detect black, white and gray
– twilight or low light
• Saccades - quick eye movements
Retina’s Reaction
Light
to
• Bipolar cells- neurons that combine info from
multiple receptors
• Ganglion cells – neurons that combine info
from multiple bipolar cells.
• Optic nerve – bundle of axons of the
ganglion cells that carry info from retina to
brain.
Vision- Receptors
Receptors in the Human Eye
Cones
Rods
Number
6 million
120 million
Location in
retina
Center
Periphery
Sensitivity in
dim light
Low
High*
Color sensitive?
Yes
No
*Why pirates wore eyepatches? Arrrr…