Unit 4 Assessment HBS 2.3 & 2.4 review

cataract

A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Cataracts are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery.

Depth perception

The ability to judge the distance of objects and the spatial relationship of objects at different distances

iris

The colored part of the eye which helps regulate the amount of light entering the eye. When there is bright light, the iris closes the pupil to let in less light. And when there is low light, the iris opens up the pupil to let in more light. The colorful structure of the eye that changes the shape of the pupil to allow for different amounts of light to enter the inner eye.

. Describe two ways in which the cow eye and the human eye differ? How are these differences linked to function?

The cow eye and human eye differ in size and shape. The cow eye has a tapetum present where the human eye does not

Cover tests

The eye doctor will ask the patient to cover one eye and stare at a small object across the room, then the doctor will ask you to cover the other eye and stare at the same thing. This test is to make sure the patient has binocular vision. Amblyopia could present from tests like this- amblyopia is a disorder where there is dimness in one eye (lazy eye)

What is refraction? What does it mean when we say that light is refracted as it enters the eye?

The fact or phenomenon of light, radio waves, etc., being deflected in passing obliquely through the interface between one medium and another or through a medium of varying density. A refraction means that the light is not bending properly when it passes through the lens of your eye.

fovea centralis

a small depression in the retina of the eye where visual acuity is highest. The center of the field of vision is focused in this region, where retinal cones are particularly concentrated.

peripheral vision

ability to see things outside of the direct line of vision. rods are responsible for this

vitreous humor

clear gel that fills the space between the lens and retina, helps give the eye its shape

retina

detects image focused by cornea and lens- the sensory layer of the eyeball which contains receptors for sight, called rods and cones

optic nerve

from the retina to the brain - nerve fibers carrying visual messages from the retina to the brain. (In order to see, we must have light and our eyes must be connected to the brain.) - The nerve at the back of the eye that transports electric signals to the brain.

rods

function in dim light and perceive shades of grey

how does astigmatism impact the way that you see?

it causes light or images to be distracted bc of the abnormal curvature of the lens

Emmetropic

normal vision

rod

photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor, cone cells. Rods are concentrated at the outer edges of the retina and are used in peripheral vision.

Cone

photoreceptor cells that are in the retina of the eye which are responsible for color vision; they function best in relatively bright light, as opposed to rod cells that work better in dim light. There are red, blue and green cones

retnis pigmentosa

refers to a group of inherited disorders that slowly lead to blindness due to abnormalities of the photo receptors in the retina

tapetum

reflects light through the retina

astigmatism

- A defect of an optical system (as a lens) causing rays from a point to fail to meet in a focal point resulting in a blurred and imperfect image. This is caused by a deviation in the curvature of the lens. - Refractive error due to an irregular curvature of the cornea or changes in the lens causing light rays to bend in different directions condition in which rays of light are not refracted equally in all direction and a point focus on the retina is not attained

Choroid

- Layer containing blood vessels that lines the back of the eye and is located between the retina (the inner light-sensitive layer) and the sclera (the outer white eye wall). -Layer behind retina that contains blood vessels

accomodation

- The automatic adjustment of the eye for seeing at different distances affected chiefly by changes in the convexity of the crystalline lens - Ability of the eye to change its refractive power to bring objects of regard at different distances into focus

20/20 vision

20/20 vision is a set measurement for normal vision this means that you see perfectly. However if you were to have 20/40 vision fterm-49or example this would mean you see in the clarity 20 feet away that a person with normal vision would be able to see 40 feet away.

myopia

A condition in which the visual images come to a focus in front of the retina of the eye because of defects in the refractive media of the eye or of abnormal length of the eyeball resulting especially in defective vision of distant objects -- called also nearsightedness. Eye is too long, needs a divergent lens with a concave shape and a negative focal length -difficulty seeing distant objects term -when light rays are focused on a point in front of the retina.

hyperopia

A condition in which visual images come to a focus behind the retina of the eye and vision is better for distant than for near objects -- called also farsightedness. - The eye ball is too short, corrective lens = convex lens to converge the light. Corrective focal length must be positive.

Color blindness test

A test where the patient has to match up different shades of color to see if the patient is able to decipher different colors, if not the patient will be diagnosed with color blindness.

macular degeneration

AMD is a common eye condition and a leading cause of vision loss among people age 50 and older. It causes damage to the macula, a small spot near the center of the retina and the part of the eye needed for sharp, central vision, which lets us see objects that are straight ahe

Optometrist

An optometrist is a trained professional to diagnose, treat, and manage conditions of the eye and some visual system disorders.Optometrists do not complete medical school however instead will further their education at a college of optometry. Optometrists may not perform surgery and are only trained to diagnose some diseases of the eye. Commonly optometrists prescribe corrective lenses to their patients for visual correction.

Lenses are described as convergent or divergent depending on how they refract light. What is the difference between these two types of lenses? Based on what you have learned, do you think the cornea and the eye lens act together as a convergent or divergent lens? Explain.

Divergent lens are prescribed to people who have myopia or near nearsightedness. They need a divergent lens because their eye ball is too long there for the light needs to come together later in the eye to provide a clear image. In contrast a convergent lens is for those who have too short of an eyeball or hyperopia. The light must come together quickly so it is able to be refracted off of the retina at the proper time. The cornea and the eye lens act together as a convergent lens, causing the light to bend and hit the retina.

Ophthalmologist

Doctors that specialize in the medical and surgical care of the visual system and eye. These doctors may be doctors of medicine or of osteopathy, they also work to prevent eye damage and disease. Ophthalmologists are licensed to provide total eye care, and perform surgery

lens

Focuses light rays onto the retina. The lens is transparent, and can be replaced if necessary. Our lens deteriorates as we age, resulting in the need for reading glasses. Intraocular lenses are used to replace lenses clouded by cataracts. The transparent orb within the eye that refracts light to the retina of the eye.

cones

Functions in bright light and provide sharp, colorful image. 3 different type of cones -Red -Blue -Green Each cone is sensitive to a different range of wavelength light

glaucoma

Glaucoma is an eye disease that affects the pressure of the eye, resulting in optic nerve damage. The aqueous and vitreous humor expand, which then covers the optic nerve, which leads to vision loss. Glaucoma is the second leading cause of blindness

after images

Optical illusions that occur when looking away after staring intently at a fixed image.

Optician

Opticians have a two year technical degree and help to aid either the ophthalmologist or optometrist in providing thorough patient care. They are able to dispense and determine the proper lens needed for a patient.

ciliary muscles

Structure containing muscle and is located behind the iris, which focuses the lens. A muscle that controls the shape of the lens to better focus the light onto the retina of the inner eye.- aid in accommodation.

How do our other senses -- taste, smell, touch and hearing -- influence communication within the body? Provide an example for each sense.

Taste- If you taste poison, your body stimulates a reflex to stop eating the potentially harmful substance. Smell- If you smell a foul odor you your reflex is to hold your breath in an effort to prevent inhalation of a potentially harmful chemical or substance Touch- If you put your hand on a hot stove, the pain receptors in your hand tell your brain to take your hand away from the hot surface. Hearing- If you hear a loud noise, such as a gunshot, your instinct is to run away from the potential danger.

. Which parts of the eye are most important when it comes to focusing light so we can see a perfect image?

The lens is the most important when it comes to focusing light so that we can see a perfect image. It focuses the light and images on the retina. As well as the pupil- the pupil is responsible for controlling the amount of light to enter into the eye

pupil

The opening in the iris, which admits light into the inner eye; muscles in the iris regulate its size and control the amount of light entering

Explain how rods and cones in the eye help the police officer in pursuit of a suspect. What other properties of sight help this officer complete his task?

The rods give the officer the vision and the cones help identify certain colors. The rods are responsible for vision at night because they are much more sensitive than cones. Rods are responsible for black and white colors which are much more easily seen in our peripheral vision than vibrant colors. At night, it is nearly impossible to see any color besides black and night which is why the rods allow the officer to adjust his eyes in darkness when needed. Depth perception also helps the officer during a chase because he is able to judge different distances quickly and react. Without depth perception he would be unable to follow and chase the suspect in his car. The rods in his peripheral vision also contribute to when he is chasing the suspect. When the suspect moves his car fast or changes lanes or swerves down a street, the rods and cones in the peripheral vision will allow the officer to detect this change and follow and chase the suspect more accurately.

Blind Spot

The small circular area in the retina where the optic nerve enters the eye that is devoid of rods and cones and is insensitive to light, cant respond to light

cornea

The transparent part of the coat of the eyeball that covers the iris and pupil for protection, bends light into an image.

Visual acuity tests

Usually performed with an eye chart 20 feet away from where you are standing with one eye covered while you read off the letters. This test is to make sure a person is not near sighted.

Refraction

What takes place in refraction is the eye doctor is determining the lense prescription the patient needs. The doctor will put a machine called phoropter up to the eyes and change the lenses while asking the patients if their vision has become more clearer or has stayed blurry.

Describe how what you see can impact other human body systems. Provide at least five specific examples of how your communication with the outside world through your eyes initiates a response in another body system

What you see impacts your other systems because of the response your brain has to the images it depicts. An image signaling danger may cause your heart to race.

Think about the optical illusions you observed in Activity 10. Explain the relationship between "seeing" with the eye and "perceiving" with the brain.

When the eye sees an image in front of it, the brain quickly assumes it is that of a past image seen. Therefore it assumes it to be something it is not because it has a memory of a similar image.

Do you think it is possible for a person to be blind, but have no problems with the structure and function of his/her eyes? Explain your answer.

Yes because the occipital lobe controls vision, not the eyes. So the eyes can have no problems and a person can be blind if they have serious damage to their occipital lobe.

aqueous humor

a clear fluid that helps cornea keep round shape

refraction

the light is not bending properly when it passes through the lens of your eye. when light travels through the lens its path is term-24bent(refracted- bent light rays into a precise point of focus essential for sharpness).

Is the response of your pupil a reflex or a voluntary action? Describe how this response is controlled by the nervous system.

the response of your pupil is a reflex, this is controlled by the nervous system strictly as means of self protection. In an effort to see as clearly as possible your eye must adjust to the amount of light present while focusing on a certain image. We do not tell our eyes to focus on objects to make them clear when it is dark instead it is a natural reaction

optical illusions

visual tracks that actually take place in the brain rather than the eye. In an optical illusion images are often mispercieved because of what we know to be true about the images we see on a daily basis sometimes this will trick our brain into not actually processing the image and instead relying on what we know to be true about images this is what is known as an optical illusion. These are significant because it shows the gap between seeing and assuming.

sclera

white hard area of the eye that protects and covers the eyeball