vision Flashcards
fibrous tunic
outer layer
protection
vascular tunic
middle layer
nutrition
retina
inner layer
transduction
sclera
white
protective
outer layer of eyeball
cornea
transparent outer surface of the eye
bends and refracts light
choroid
highly vascular
very thin
lines nearly the entire inner surface of sclera
brown
designed to prevent light rays from bouncing back out the eye ball
iris
coloured part of the eye
being the anterior chamber
controls the amount of light entering the eye
retina
dark spot - macula and fovea
light spot - optic nerve
astigmatism
cornea improperly shaped
light entering the eyes os not properly bent
inability to properly focus the image onto the retina
glaucoma
cilliary bodies clog up
improper drainage of waste
excess of aqueous humour
intraocular pressure
presbyopia
old sight
inability of the lens to accomadate properly
loss of elasticity in the lens with age
albinism
due to lack of pigment in the iris
a pinkish hue of the eye
fractional eye movement
small involuted eye movements that occur during visual fixation
- mircosaccades
- ocular microtremor
- ocular drift
saccadic movements
quick, simultaneous movements of both eyes in the same direction
smooth pursuit
ability of the eyes to smoothly follow a moving object
vergence movements
simultaneous movement of both eyes in opposite directions
vestibule ocular reflex
reflex eye movement that stabilises the images on the retina
works in total darkness or when eyes are closed
optokinetic reflex
allows the eye to follow objects in motion when the head remains stationary
retina
outer segment - components for light absorption
inner segment - protein synthesis and energy production
phototransduction
- light strikes the retina
- the retinal is transformed, opsin also transformed
- generation of electrical impulse, transmits through the optic nerve to the brain for processing
horizontal cells
laterally interconnecting neurons in the outer layer of the retina
photoreceptors
high light levels - only cone mediated vision is sensitive to light as rods are bleached at high levels
low level light - only rod mediated vision is sensitive enough to detect light
rods
night vision
peripheral vision
poor resolution
motion sensitive
high convergence
cones
daylight vision
foveal vision
high resolution
colour sensitive
low convergence
midget ganglion
small sized centric trees and cell bodies
parasol ganglion
large sized dendritic trees and cell bodies
photosensitive ganglion cells
contain their own photopigment
respond to light even in absence or rods and cones
project to the SCN
retinal ganglion cells
exit the eyes at the optic disc and travel via the optic nerve to the optic chiasm
optic chiasm
half the fibres cross to hemispheres opposite to left and right visual hemifeilds
lateral geniculate nucleus
80% of the optic fibres terminate
in thalamus
superior coliculus
20% of optic fibres terminate
in midbrain
ventral pathway
what
temporal lobe
object recognition
dorsal pathway
where
parietal lobe
appreciative agnosia
damage to occipital lobe
inability to perceive entire perceptions
unable to draw/copy or recognise objects
perceive local properties but not wholes
appreciative agnosia 2
image to parietal lobe
inability to recognise objects if contour degraded or in a atypical position
hemispatial neglect
damage generally in right parietal lobe pr right temproroparertial junction
