eye, vision Flashcards
what are the 3 parts of the eye (main)
pupil, iris, scalera
what is a scalara coil
measures eye movement by sitting on the eye
where does light hit after passing the cornea
to the retina
high center of what in the middle of the retina
photoceptors
what are the muslces attaching the lense and change shape of lense
ciliary muscles
what can the cillry muscles do
change shape of the lens
how does the brain reverse image
left to right
post retinal processing is what
what is a diopter
is a measure of lens focussing power - reciprocal of focal length in meters - 1D=1m
what 2 things effect lens strength
curvature and refractive index
how does the lens change shape
either curved and oval or flat - aka accomodation
ciliary muscles can contract and relax - which is loosening of fibres
contract
what state will your eye be if relaxed
focusing on something’
round shape is for what
close object
flat lens is for what
something far away
parasympathetic nervous system
concave lens of glasses is
short sighted
short sighted is aka
myopia
how does a concave lens help
reduces the refraction and focus
what is hypermetropia
far sighted
how does the pupil adapt to light
changes diameter- smaller = too much light VV
whats the range for pupil size when changing
2-8mm
whats the proper name for pupil
sphincter pupillae
why is a smaller pupil better
links to more light be accessible but also creates a high quality image - like a pinhole camera which has more depth
depth of field is what when small pupil
longer / deeper
pupil size can help with which condition
myopia
what is a ophthalmoscope
an object that shines light into a retina
photoreceptors in high amount are where
retina middle
rods and cones make up what
photoreceptors
what are the 5 cells in photorecptors
cones/rods, horizontal cells, biopolars, ganglai cells and amacrines
what do ganglia cells do
fire like neurons
do photorecptors have ap
no
do ganglia in photorecptors have ap
yes
what forms the optic nerve
ganglai cells
why are structures in the front foveal receptors pushed to one side
reduces light / scatter absorption
what is acuity
sharpness
what happens to receptors when they are saturated and cannot detect light
they become bleached
what is photopigment
a pigment that the chemical state depends on its degree of illumination
what 2 molecules used to form photopigment
retinal and opsin
retinal and opsin are the what state
bleached
the light photon interacts with rhodopsin causes what
configurational change
released opsin activates PDE - phosphodiesterase via …
transducin G protien
closure of NA channels cuases hypeerpolerisation of cell due to what leak
K
ganglion cell modifies the membrane potential of a what cell
bipolar
changes in firing of ganglion cell bipolar can be
excitatory or inhibitory
rod and cone hyperpolarization results in less
neurotransmitter release - glutamate
what is the unit that the eye can function across of luminance
10^15
what is scotopic vision
low light vision
are rods or cons for low light
rods - because low acuity and high sensitivity
is high light / photopic rods or cones
cones only - too much light will bleach the rods
mesopic is what
medium light level
mesopic what levels is everything
medium
does mesopic have rods or cones
both
what are the 4 mechanisms adapting to lumminance
pupil size, cones and rods switch dark adaptation ( bleaching and regeneration) and field adaptation
what is field adaption
light adaptation, automatic gain control within photoreceptor - calcium release mechanism
sensitivity verus acuity is what
an adaptation which is a constant trade-off of the 2
Rods are more sensitive than cones t or f
T
how long does it take to regenerate rods cells
20min
under mescopic conditions rods and cones may..
converge together
visual sesnitivity gradually increases over 20min in
dark
cones adapt faster but rods
take over as their threshold is lower
field adaptation copes with fast ..
changes in light
biopolars, horizontals and amacrines do what
retinal processing partically, reducing things of interest, changes - spacial and temporal
the ganglion cell is the final output of what
the retina
each ganglion cell may repsond to
many photoreceptors
use light shone on a retina to find what
the ganglion receptive field
Some photoreceptors excite the ganglion cell, some inhibit.
Forms a centre-surround shape, causing
lateral inhibition
lateral inhibition is
mediated by horizontal cells
lateral inhibition explained-
the surrounding context impacts what your retina sees
1 rod cell and 3
cone cell
what can colour be defined by 2
saturation and hue
where does colour processing take place
the retina
ganglion cells dont respond to which colours
green blue or red - alone but do combinations
colour constancy is ..
when colours tend to look the same despite large changes in wavelength of illuminating light
colour blind or deuteranope is
lack of green receptor
which part of brain does a left visual enter
right
where does the optic nerve split
optic chiasm
informtaion if relayed to where via the lateral geniculate nucleus - in thalamus
visual cortex
