Vision I Flashcards
visual acuity
the ability to see fine lines and details (its what gives us 2020 vision)
visible light
the portion of the electromagnetic spectrum that we are able to see
what characteristics of light are we not able to see
lightwaves
how can we characterize light waves
by their variations in length, size, height, and distances between each wave
what does the length of the light wave determine
hue of the light (the color that we are able to see)
what does “intensity” of a light wave mean
the amplitude/how high the peaks are
what does the intensity of a light wave determine
how bright the light we perceive to be is
what does “purity” of a light wave mean
how many singular waves makeup the single light wave
what does the purity of a light wave determine
determines how saturated the color is; not enough waves gives it more of a lighter color whereas a lot of waves making up a single lightwave will make a very deep and saturated color
what are the main parts of the eye (ordered)
cornea, iris, pupil, lens, retina, optic nerve
what is the cornea and what is its purpose
clear smooth outer tissue that bends and focuses the light wave that enters the eye in order for the light waves to enter in such way that they freely pass through the pupils
what is the iris and what is its purpose
the iris is the colored part of the eye that controls the size of the pupils; thus controlling the amount of light that enters the eye
what is the pupil and what is its purpose
the pupil is the black hole in the middle of the iris where light enters into the eye
what is the purpose of the muscles behind the iris
control the shape of the lens to bend and focus light again onto the retina and diff distances
in what ways can the muscles behind the iris bend the shape of the lens
the muscles will make the lens shape flatter for objects that are far way and rounder for objects that are closer
what is the retina and what is its purpose
the retina is a layer of light sensitive tissue that lines the back of the eyeball and receives light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition.
what makes up the retina
the retain is made up of cones, rods, bipolar cells and ganglion cells
what is the retina referred to ?
the retina is also referred to as the interface between the world of light outside the body and the world of vision inside the body
what are the two types of photoreceptor cells within the retina
rods and cones
what do these photoreceptor cells contain
they contain light sensitive pigments thats transduce light into neural impulses
when are our cones activated
they are active under direct color, operate under normal daylight conditions, and allows us to focus on fine detail; a lot of photons are needed to activate the cones
where are the cones more densely packed
they are more densely packed in the fovea of the retina
what is the fovea
it is the area of the retina where vision is the clearest
when are our cones activated
our cones are activated under lowlight conditions
what makes our rods more sensitive than cones and at what cost
our rods are easily activated (they can be activated by a single photon unlike our cones which need a large amount of photons to be activated) however this comes at the cost of our rods not being able to detect high frequencies of color like our cones can
how many cones and rods are there in our retina and what difference does it make
there are 6 million cones lined up in our retina and 20 million rods; the cones are more densely packed in our fovea which is in the middle of the retina but the rods are more dispersed thus explaining why objects off to the side in our peripheral view are not clear
what is the purpose of the bipolar cells and where are they located
the bipolar cells are located directly above the rods/cones and they collect neural signals and then transmit them to the retinal ganglion cells
what is the purpose of the ganglion cells
the ganglion cells serve as the final output neurons of the vertebral retina which collects information about the visual world from bipolar cells and amacrine sells (retinal neurons)
what are amacrine cells
they are interneuron cells between bipolar and ganglion cells that are in the visual cortex and respond to basic elements
what do the axons of the ganglion cells form
they form the optic nerve
where does the optic nerve begin
the optic nerve begins in the retina
describe what happens/the structure of the optic nerve after its beginning in the eye
beginning in the retina, the axons of the optic nerve cells called RGCs come together to leave the eye at a region called the optic disc thus forming the optic nerve.
what happens after the nerve leaves the eye
the optic nerve extends to a structure called the optic chiasm where it meets the optic nerve from the other eye
what happens at the optic chiasm
the optic nerve fibers carrying info from the side of nerve cross over to the other side of the brain while those carrying info from the side closest to the temples stay on the same side
what happens when the optic nerve begins to leave the optic chiasm
the nerve becomes known as the optic tract (most of the fibers in the optic tract end in the lateral ganiculate nucleus of the thalamus and from there info is passed to the visual cortex
what two pathways are included in the visual cortex
dorsal and ventral
what is the dorsal stream
travels up from the occipital lobe to the parietal lobe and to mid and upper parts of the temporal lobes and expresses where the object is
what is the ventral stream
the ventral stream travels down from the occipital lobe into the lower levels of the temporal lobe and into the hippocampus and it detects the what of the object
memory refresher*** what is the hippocampus responsible for
the hippocampus is responsible for creating new memories and integrating them into a network of knowledge so that they can be stored indefinitely in other parts of the cerebral cortex
what are these pathways used for
they are part of the perception processes of the neural system that help to detect shape
what is the neural system for perceiving shape
area VI
what is area VI
area VI contains populations of neurons, each tuned to respond to edged oriented at each population in the visual field (some neurons fire when we perceive objects in horizontal others in vertical others in diagonal
describe what illnesses are associated with the eye and its general anatomy
the eye can either be too long (nearsightedness - myopia) or too short (far sightedness-hyperopia)
what are the signs of myopia
one will be able to see nearby but not far away because the image is focused at the front of the retina
what are the signs of hyperopia
can see far away but not up close because the images that are far are focused behind the retina
what are the solutions to both of the illnesses associated with the eye and its general anatomy
eyeglasses/contacts or lasik
what impact would the glasses/eye contacts have on eyes with either myopia or hyperopia
they would provide additional lenses to help focus the light more directly
what impact would lasik have on the other hand
it would reshape the eyes cornea to help focus light more directly
what kind of damages can happen in the optic nerve
trauma, stroke, tumors, glaucoma
what is another word for visual defect
anopsia
what happens if damage occurs before the optic chiasm
the pt will experience blindness in the eye that supplies that optic nerve
if damage occurs in the middle of the optic chiasm
then the pt will experience blindness in the lateral fields of both eyes due to the way the fibers from the nasal side of the retina cross over
if damage occurs in the optic tract
then half of the visual field will be lost in both eyes
in regards to the visual cortex what happens if there is permanent damage to the large region of the lateral occipital lobe (area of the ventral stream)
the pt will exp visual formagnosia there will be impaired sight but ability to touch and recognize objects = normal
what happens if there is brain damage to the parietal lobe or the section of the dorsal stream
the pt will likely have a difficult time using their vision to guide/reach objects but will not be able to recognize what the objects are
what color does the s cone represent
blue
what color does the rod represent
white
what color does the m cone represent
green
what color does the L cone represent
red
