Vision Flashcards
What are the 2 principles of vision?
- Perception is dynamic - we perceive change
- we perceive constancies in a changing environment
What is the electromagnetic radiation continuum?
- is generated when an atom emits a “particle” called a photon
- the energy of photons determines their wavelength
- different wavelengths give rise to the perception of different colours
True or false: the human eye is only capable of detecting light within a narrow range of wavelengths
True
What is the effect of a short wavelength?
Ultraviolet light
(Gamma rays, X rays)
What is the effect of a long wavelength?
Infrared light
(radar, radio)
Where is the Retina positioned in the eye?
Above the line of sight and Fovea at the back of the eye
What is Saccades?
Our eyes are constantly moving
- if an image stays stable it disappears on the retina (the photoreceptors stop firing) and the brain fills in the missing spaces
Describe the stationary blind spot
We have a stationary blind spot where the optic nerve enters the eye and we are unaware of it
What controls the shape of the lens to accommodate near or far targets?
the ciliary muscles
To focus on a far target what happens to the lens?
Lens flattens
To focus on a near target what happens to the lens?
Lens rounds
What are the properties of cones?
- fast dark adaptation
- low dark sensitivity
- “yellow” sensitive
- high acuity
(fovea and periphery)(6 million)
What are the properties of Rods?
- slow dark adaptation
- high dark sensitivity
- “green” sensitive
- low acuity
(Mainly peripheral vision) (120 million)
What is the Duplex retina theory?
Schultze proposed that the rods and cones form two separate visual fields; Photopic and Scotopic
What is the Photopic visual field in the Duplex Retina theory?
Bright light vision via cones
- “day blind” without cones
What is the Scotopic visual field in the Duplex Retina theory?
Dim light vision via rods
- “night blind” without rods
What cells do Receptor cells synapse with?
Bipolar cells
What cells do bipolar cells synapse with?
ganglion cells
What do Horizontal cells do?
connect different receptor or bipolar cells
What do Amacrine cells do?
connect different bipolar or different ganglion cells