Vision Flashcards
How does light travel through the eye?
Cornea –> pupil –> lens
What is the cornea?
A clear hard covering that protects the lens
What is the pupil?
An opening in the iris in which light enters the eye
What is the lens?
The structure behind the pupil that bends light rays to focus images on the retina and allow larger area of visual space in the small eye area
What is the iris and it’s function?
- A muscle that makes up the colored part of the eye
- adjusts pupil to control the amount of light that enters
the eye
What is the retina?
- The thin layer of tissue that lines the back of the eye
- The lens bends light rays to focus light on the retina
What is the process of Accommodation?
The process by which muscles control the shape of the lens to adjust it to view objects at different distances
What are the cells in the retina called?
Photoreceptors called rods and cones
What is the purpose of photoreceptors?
These convert light energy to neural impulses
Explain the pathway of light through the eye in terms of cells
Ganglion cells –> amacrine cells –> bilayer cells –> horizontal cells –> photoreceptor layer (rods and cones)
What are rods?
- One of two photoreceptors
- Located on the outer periphery of the retina
- used in vision at night
- very sensitive to light
- become “bleached” in the morning when sudden bright light hits the eye
- more numerous
- protein contained in these cells called rhodopsin
What are cones?
- One of two photoreceptors
- responsible for our colour vision
3 photosins: short (blue), medium (green), long (red) - function well in bright light
- give our vision sharpness and detail
- best in bright light
- less numerous
- protein contained in these cells called photopsins
What is the fovea?
- A spot in the back of the retina that contains the highest concentration of cones
- Because of this high concentration of cones, when ligh hits the fovea, the clearest image we can see is produced
Explain the difference in photoreceptors in humans and dogs and how this affects our vision
While both dogs and humans have more rods than cones, dogs have less cone cells than rod cells compared to humans
This explains why dogs have better night vision that humans ( the more rod cells ) and why they have poor detailed vision and poorer colour vision (less cones than humans)
what are the theories of the perception of colour?
The trichromatic colour theory
- colour is perceived by mixing wavelengths of light
The opponent process theory
- cones are linked together in opposing colour pairs
and so when one fires, the other cannot