Lesson 4 Study Guide

depth perception

the ability to judge the distance of objects and the spatial relationship of objects that light to the interior - with 1 eye, field of vision appears two dimensional - with 2 eyes, the eyes see & the brain processes different views of the same object - simply, ability to see things in three dimensions - length, width, and depth - and to perceive how near or far away people and objects are.

accomodation

adjustment of the optics of the eye to keep an object in focus on the retina as its distance from the eye varies. It is the process of adjusting the focal length of a lens.

cones

allow us to perceive color in normal lighting conditions - in fovea, no rods but many cones

rods

allow us to see in dim light - provide peripheral (or side) vision - are responsible for dark adaptation -most sensitive to movement/motion - less sensitive to color perception. - perceive shades of gray - rods are more than cones

how does the eye perceive color?

by signals from the cones in the retina.

vision screening & vision testing

can each be a window of opportunity for healthy sight - find out how they are different.

refract

change direction

iris

colored portion of the eye; smooth muscle; causes dialation and constriction of the pupil; by doing so it regulates the amount of light entering the pupil, first ring of tissue from pupil. - ring-shaped membrane inside the eye that surrounds an opening in the center.

hyperopia corrected with

converging lens, convex lenses

astigmatism

cornea or lens is irregular in shape which causes light entering the eye to focus on 2 points rather than single point. causes headaches, blurred, etc can be corrected by refractive surgery, glasses, or contacts

how can corrective lenses be used to refocus light and resolve myopia and hyperopia?

corrective lenses work by modifying the path of the light as it approaches your eye such that between the artificial lens and the lens of your eye - the light focuses on the retina.

how is life impacted by a vision disorder?

depends on the severity - you may get glasses - but if you are full on blind, then life will be very hard

myopia corrected with

diverging lenses, concave lenses

cornea & lens

focus light

how does an error in the structure or function of the eye relate to disease or dysfunction?

if the eye is too long or to short, then myopia or hyperopia can occur - if the cones are not properly receiving color, then colorblindness will occur & other problems

ciliary muscles

in the eye assist adjustment of the lens

different types of cones come together to...

interpret colors other than red, blue and green

slit lamp exam

is a magnified analysis of your eye from front to back

lens

is composed of transparent, flexible tissue and is located directly behind the iris and the pupil. - is the second part of your eye, after the cornea, that helps to focus light and images on your retina.

concave lenses

is thinner at the centre than at the edges. Rays of light that pass through the lens are spread out (they diverge).

vitreous humor

jelly-like substance that fills the inside of the back part of the eye - over time, the vitreous becomes more liquid and can detach from the back part of the eye, which can create floaters.

myopia & hyperopia

light can't focus on the retina causing faraway objects to seem blurry, images are formed in front of the retina

myopia

light can't focus on the retina causing faraway objects to seem blurry, images are formed in front of the retina, nearsightedness.

what does it mean to have 20/20 vision?

means that the test subject sees the same line of letters at 20 feet that a normal person sees at 20 feet. - 20/40 vision means that the test subject sees at 20 feet what a normal person sees at 40 feet.

converge

meet at a point

visual perception

one of the senses, consisting of the ability to detect light and interpret it as the perception known as sight

3 different types of cones

red blue green

peripheral vision

side vision - the ability to see objects and movement outside of the direct line of vision - is the work of the rods, nerve cells located largely outside the macula (the center) of the retina. the rods are also responsible for night vision and low-light vision but are insensitive to color. as opposed to central vision. - due to their proximity to the edge of the retina, rods are responsible for this aspect of vision - better for detecting movement than for processing sharp images, and is most often stronger in the dark

pupil

space or black hole through which the light passes

how does the eye perceive optical illusions?

- certain types of spatial arrangements and certain types of motion will cause the brain to misinterpret the information, creating an optical illusion

how does the eye perceive depth perception?

- combination of the visual images (from the left occipital and the right occipital) is what allows us to have depth perception

sclera

- tough white outer coating of fibrous tissue that covers your entire eyeball (all the way around) except for the cornea - muscles that move the eye are attached to the sclera. - maintains the shape of the eyeball, protects the eye from serious damage

cornea

- transparent dome-shaped tissue that forms the front part of your eye - functions as a window and allows light to enter your eye - also begins the process of focusing light rays that allow you to see words and images clearly - provides 65-75% of your eye's focusing power.

retina

a layer at the back of the eyeball containing cells that are sensitive to light which lines the inside of the eye - cells in the retina convert incoming light into electrical impulses -t hese electrical impulses are carried by the optic nerve (which resembles your television cable) to the brain, which finally interprets them as visual images.

aqueous humor

the clear fluid filling the space in the front of the eyeball between the lens and the cornea.

hyperopia

the light focuses behind the retina because the eyeball is too short, farsightedness.

impulses from rods to cones pass from

the nerve cells to the optic nerve

how do the eye and the brain work together to process what we see?

the retina, which receives the focused light, has cones and rods which translate color and faint light to chemical and nervous signals so the the optic nerve, which connects to the brain, sends it to the occipital lobe and other parts to be processed into our comprehensible picture.

blind spot

the small circular area in the retina where the optic nerve enters the eye that lacks of rods and cones and is insensitive to light - the optic nerve exits the eye at the retina on its way to the brain. - since this area of the retina does not have receptors that respond to light, it is referred to as the blind spot. - an image that falls on this area can not be seen. - normally people do not recognize the blind spot because the eyes are always on the move and the brain ignores this "hole" in visual input

convex lenses

thicker in the middle than the edges When light travels through lenses, refraction occurs. The light bends either outward or inward, it depends on the lens.

how does what we see impact other human body systems?

what we see can send panic signals to our endocrine system and then have an effect on systems from there. also, if we see something we are scared of, it can stop our breathing, make us scream, close our eyes, etc.What we see can send panic signals to our endocrine system and then have an effect on systems from there. and also if we see something we are scared of it can stop our breathing, make us scream, close our eyes and other things.

optic disc

where the optic nerve converges and exit the eye, no light-sensitive cells to detect light rays, results in a break in the visual field, known as a blind spot - no photoreceptors, so cant see visual images which makes it a natural blind spot

eye dilation exam

your pupil in front of the eye has been opened using special drops