2.4 Quiz

optic nerve

the bundle of nerve fibers that carry information from the retina to the brain

tapetum

The colorful, shiny material located behind the retina. Found in animals with good night vision, the tapetum reflects light back through the retina.

What is visual perception? What is visual acuity?

visual perception is the ability to perceive our surroundings through the light that enters out eyes. visual acuity is how sharp or clear our vision is.

cornea

a tough, clear covering over the iris and the pupil that helps protect the eye. light bends as it passes through the cornea. this is the first step in making an image on the retina. the cornea begins bending light to make an image. the lens finishes the job.

describe Glaucoma

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 one of the leading causes of blindness

What are the tests and procedures in a routine eye exam?

eye muscle test, visual acuity, refraction assessment

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

eye works like a camera and lens. brain helps translate image to something we understand

Explain the importance of the fovea centralis.

fovea centralis allows for central vision and helps with actions like driving and reading

describe Colorblindness

inherited usually. Poor or deficient color vision is an inability to see the difference between certain colors, but color is still seen. But true color blindness, in which everything is seen in shades of black and white, is rare. The most common color deficiency is an inability to see shades of red and green. Next is an inability with shades of blue and yellow. Seeing colors across the light spectrum is a complex process that begins with your eyes' ability to respond to different wavelengths of light. If your cones lack one or more wavelength-sensitive chemicals, you will be unable to perceive one or more of the primary colors → red, blue or yellow.

describe retinitis pigmentosa

inherited, slowly leads to blindness due to issues in the rods and cones (photoreceptors), rp is the result of harmful changes in any one of more than 50 genes, genes carry instructions for making proteins that are needed in cells within the retina called photoreceptors

How does what we see impact other human body systems?

most of what we do is in response to sight. our sight guides out actions.

How is light focused by the eye?

mostly cornea and lens, but also fluid, pupil, and iris

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

myopia is nearsighted, and hyperopia is farsighted. myopia is corrected with a concave (diverging) lens and negative prescription. hyperopia is corrected with a convex (converging) lens and positive prescription.

describe two astigmatism

nearsighted and farsighted

What does it mean to have 20/20 vision?

20/20 is considered normal visual acuity. it means you can see what a normal person sees at 20 ft.

describe Cataracts

A cataract is a clouding of the normally clear lens of your eye. Most cataracts develop when aging or injury changes the tissue that makes up your eye's lens. Most cataracts develop slowly and don't disturb your eyesight early on. But with time, cataracts will eventually interfere with your vision.

Afterimages

Afterimages are optical illusions that occur when looking away after staring intently at a fixed image or color. The constant light stimulating the retina causes the cones in that area to become fatigued. After looking away from the image, the less-stimulated cones, which are not fatigued, still function. The resulting image lasts briefly and because it comes only from the less fatigued cones, is perceived as a negative image.

Astigmatism

Astigmatism is a condition in which the cornea or the lens is irregularly shaped. This shape change causes incoming light rays to refract and converge improperly. The light rays do not focus at the specific point on the retina, resulting in a blurry or distorted image. Astigmatism may be corrected with eyeglasses, contact lenses, or refractive surgery.

describe Age-Related Macular Degeneration

Chronic eye disorder that causes blurred vision or a blind spot in your visual field. there are two types: wet and dry. Wet ARMD is generally caused by abnormal blood vessels that leak fluid or blood into the macula. The macula is in the part of the retina responsible for central vision acuity. Dry ARMD is caused due to thinning of the macula.

Color Vision

Color vision is possible through the retina of the eye. The retina possesses two special types of nerve cells known as photoreceptors- rods and cones. Impulses from rods and cones pass through nerve cells to the optic nerve.

Depth Perception

Depth perception is the ability to judge the relative distances between objects in three dimensions. With one eye, the field of vision appears two-dimensional. With two eyes, the eyes see and the brain processes different views of the same object.

Cones

Function in bright light and provide sharp, colorful images. There are three different types of cones: red, blue, and green. Each type of cone is sensitive to a different range of wavelengths of light. Different cones function together to interpret colors other than red, blue, and green. If any of the cones malfunction, color deficiency or color blindness occurs.

Rods

Function in dim light and perceive shades of gray

Optical Illusions

Optical illusions are visual tricks that actually take place in the brain rather than the eye. The visual cortex of the brain deciphers images sent from the eye, however surrounding objects, intense colors, distortions of expected patterns, and preconceptions can cause the mind to "see" and interpret an image differently.

Peripheral Vision

Peripheral vision is the ability to see things that fall outside of the direct line of vision. Due to their proximity to the edge of the retina, rods are responsible for this aspect of vision. Peripheral vision is better for detecting movement than for processing sharp images, and is most often stronger in the dark.

vitreous humor

The thick, clear jelly that helps give the eyeball its shape.

sclera

The thick, tough, white outer covering of the eyeball.

Accommodation

Two parts of the eye - the cornea and the lens - focus light on the retina. The cornea does most of the work, but it cannot change shape. Fine adjustments are carried out by the lens. Accommodation is the combination of reflex actions by which the lens of the eye changes to keep the focal length, the distance between the center of the lens and its focal point, constant. Ciliary muscles in the eye assist adjustment of the lens.

iris

a muscle that controls how much light enters the eye. it is suspended between the cornea and the lens. human irises comes in many colors: brown, blue, green, and grey

aqueous humor

a clear fluid that helps the cornea keep its rounded shape

lens

a clear, flexible structure that makes an image on the eye's retina. the lens is flexible so that it can change shape, focusing on objects that are close up and objects that are far away

retina

the layer of light-sensitive cells at the back of the eye. the retina detects images focused by the cornea and the lens. the retina is connected to the brain by the optic nerve.

blind spot

the place where the optic nerve leaves the retina. each eye has a blind spot where there are no light-sensitive cells

pupil

the pupil is the dark circle in the center of your iris. its a hole that lets light into the inner eye. your pupil is round.

How does the eye perceive depth, color, and optical illusions?

with the combination of images, it allows our eyes to perceive depth. the cones allow us to see color. optical illusions are made by our eyes and brains being tricked. the main parts for these processes include occipital lobe, visual cortex, rods, and cones.