Vision Flashcards
How does light travel?
Via electromagnetic waves or particles called photons
What is luminance?
the % light that is reflected from each wavelength of an object
What muscles cause the iris to a) contract and b) dilate?
a) circular muscle
b) radial muscle
What is accomodation?
Bringing different objects into focus by changing the shape of the lens
What is:
1. Myopia
2. Hyperopia
And how can they be corrected?
- Difficulty seeing far away things as the lens is too strong, need concave glass
- Difficulty in seeing close up things as the lens is too weak, need convex glass
What is the ‘near point’?
he nearest distance to the eye at which an object is accurately focused on the retina at full accommodation
What are the properties of the rod cells?
Used for scotopic vision at low light levels
- High sensitivity to light
- Slow recovery in the dark
How are the cone cells different?
Used for photopic vision at high light levels?
- Low sensitivity for light
- Have a quick recovery in the dark
- Used to detect colour
How are photons absorbed?
By specialised pigment rhodopsin located in the rod cells. When activated, inhibits the bipolar cell.
How is a ganglion (M cell) organised?
Centre-surround organisation:
Inhibitory surround and exitatory centre
Describe the passage of visual information into the brain
- Signal from left eye goes to the right and vica versa at the optic chiasm
- Optic tract then leads to the lateral geniculate nucleus (LGN)
- Divides into optic radiations before being received in the striate cortex
What is the trichromatic theory for colour perception?
Colour perception is based on three primary colours corresponding to three receptor types in the retina
What is the opponent processing theory?
Colour perception is based on the activity of 3 oponent systems
- White vs Black
- Blue vs Yellow
- Red vs Green
What are the 3 types of opsin?
L-opsin, M-opsin and S-opsin
What are the 3 types of opsin and what colours are they receptive for?
S-Opsin - blue
M-Opsin - green
L-Opsin- red
