Vision Flashcards
Are we limited by our visual system
We only respond to a narrow range of wavelengths which is the human visible spectrum
What does the iris do
Controls how much light enters the eye
What does the pupil do
It is a circular hole where the light enters the eye
What is the cornea
It is a curved transparent layer covering the iris and the pupil
The curvature is responsible for bending incoming light to focus it on the back of the eye
What is the lens
It does the same as the cornier but can change its curvature to accommodate as it is made up of cells
What does the retina do
It is a thin membrane that is at the back of the eye it is technically part of the brain
Receives light that the lens has focussed and convert it into neural signals for the brain
What is the fovea
It is the central part of the eye responsible for acuity (sharpness of vision)
Retina is spread aside to let the light directly on the cones
What are ganglion cells
Output neurons of the retina. Depart eye via optic nerve to reach brain
What is the blindspot of the eye
Is a region of the retina that contains no rods or cones - nothing to detect vision
Why don’t we noticed that we have a blindspot
It is always there but our brain fills in the gaps so that we don’t notice it
What is myopia?
Near sightedness images are focused in front of the rear of the eye this can be due to the cornea being to steep of the eyes being too long
What is hyperopia?
Farsightedness the focal point goes beyond the retina this can be due to the cornea being too flat for the eyes being too short
What are rods
They work in low light monochromatic and responsible for peripheral vision
Allow us to see basic shapes and forms and are more plentiful long and narrow
What are cones
They are less numerous they work in bright light and allow us to see colour
They are responsible for central vision and fine detail
What is the optic nerve
It contains the axons of ganglion cells and travels from the retina to the brain
Optic chiasm?
X shaped structure that allows a crossing over of the optic nerves.
Allows the visual cortex to receive the same hemispheric visual field from both eyes
Lateral geniculate?
A relay centre in the thalamus for the visual pathway it receives major sensory input from the retina
What is the primary visual cortex
It is the part with the occipital lobe that receive visual information from the optic nerve
What is the V4 system
Colour
What is the MT/V5 system?
Movement
What is V1/primary system?
Optic chiasm
Lateral geniculate
Primary visual cortex
Trichromatic theory of colour vision?
Colour vision is based on our sensitivity to 3 primary colours
This is consistent with the three types of cones in our eyes and explains colour blindness
What is the opponent process theory of colour vision
Colour vision as a function of complimentary opposing colours
Red versus green
Blue versus yellow
Opponent colours competing with each other
What are some causes of blindness
Cataracts Glaucoma Macular degeneration Diabetic retinopathy Childhood blindness
What are cataracts
Change on lens looks cloudy more opaque and less light coming in
What is glaucoma
Pressure build up damaging the optic nerve
What is macular degeneration
Central vision loss
What is diabetic retinopathy
Damaged blood vessels - patchy loss of vision
What is colour blindness
Often due to the absence or a reduced number of one or more types of cones due to genetic abnormalities
What are the three types of colour blindness
Monochromacy- only one time of cone - lose all colour vision
Dichromacy - two types of cones, missing one
Trichromacy - normal vision
What is motion blindness
Occurs when unable to string together images processed by the brain into perception of ongoing motion
What is visual agnosia
The inability to recognise objects despite normal ability to describe the shape colour etc
Occurs when there is damage in brain areas that piece together visual elements
Cortical blindness and blindsight?
Damage to V1/primary
Can identify shapes and location
Route of information flow to visual association areas is blocked however visual information is still reaching the visual association cortex without going through v1
