Retinal Processing Flashcards
What are the three layers of the retina?
Photoreceptors (rods and cones)
Pigment epithelium
Sclera
What is the first cell type light is most likely to encounter as it enters the eye and moves towards the back of the eye?
Ganglion cell
Which photoreceptor is bigger?
Rods
Ganglion cells are located everywhere except
At the fovea
There are more photoreceptors/mm^2 in the (nasal/temporal) retina
Nasal
Where are there more rods than cones? More cones than rods?
More rods in retinas
More cones in fovea
In which retina is the optic disc located? What is the consequence of this?
Nasal, causes a blind spot
Which are more sensitive, rods or cones?
rods
Why is it easier to see a bright star on a dim night when you look next to it?
Because there are more rods on the parafovea which are more sensitive
True/False? Cones can adapt to dark light just as well as rods can
False
What is the difference between scotopic and photopic vision?
Scotopic: dark
Photopic: well lit
What is the photochromatic interval?
The increase in sensitivity going from photopic to scotopic vision
What is the Purkinje shift?
The shift in optimal wavelength going from photopic to scotopic vision
How do On-center RGCs react when light is shone: Directly on centre? Dimly on centre? Directly off centre? Dimly off centre? Everywhere?
Strongly Weakly Weakly Strongly Weakly
How do Off-center RGCs react when light is shone: Directly on centre? Dimly on centre? Directly off centre? Dimly off centre? Everywhere?
Weakly Strongly Strongly Weakly Weakly
True/False? A photoreceptor is connected to just an on or just an off-centre RGC
False
What are Centre-Surround interactions most responsive to? What does this result in?
Contrast, Results in non-uniform receptive field structures (enhances edge information in scenes)
Compare parasol and midget cells in terms of their Receptive fields Conduction velocity Responsiveness to rapid contrast change Color response
Parasol RGCs: Large RF High Conduction v v. responsive to rapid contrast Poor color response
Midget RGCs Small RFs Low conduction v Poorly responsive to rapid Good color response
Why is visual acuity lower in the periphery?
Optical and biological factors
RFs are larger
How does the contrast sensitivity/spatial frequency curve change in a person with myopia?
Shifted to the left
