Lesson 2: Vision

Question 1

The lens of an eye can become thinner or thicker based on the distance of an object. Which structure is responsible for the lens’s ability to change its shape?

(A) Ciliary Body
(B) Retina
(C) Cornea
(D) Aqueous Humor

Answer 1

(A) Ciliary Body

The Ciliary Body is the structure that changes the thickness of the lens. The ciliary body is composed of suspensory ligaments and ciliary muscle, which on top of changing the shape of the lens also secretes aqueous humor.

Question 2

Inferior to the lens is the ______________. This is separate from the _____________, which filled with a jelly-like substance known as the vitreous humor, that helps to suspend the lens in place while also providing some structure to the eye itself.

(A) Anterior Chamber, Ischemic Chamber
(B) Anterior Chamber, Vitreous Chamber
(C) Posterior Chamber, Vitreous Chamber
(D) Posterior Chamber, Ischemic Chamber

Answer 2

(C) Posterior Chamber, Vitreous Chamber

Inferior to the lens is the Posterior Chamber. This is separate from the Vitreous Chamber, which filled with a jelly-like substance known as the vitreous humor, that helps to suspend the lens in place while also providing some structure to the eye itself.

Question 3

CRB Which of the following is an eye disorder that is often caused by a blockage in the Canal of Schlemm? (This canal allows for aqueous humor to drain, but when blocked, pressure builds up in the posterior chamber.)

(A) Glaucoma
(B) Astigmatism
(C) Hyperopia
(D) Myopia

Answer 3

(A) Glaucoma

Glaucoma is an eye disorder that can be caused by blocking the Canal of Schlemm, which will prevent aqueous humor from draining. building up pressure in the posterior chamber of the eye.

Question 4

A common issue with flash photography is the “red eye effect”. What part of the eye anatomy causes the red eye effect, and how?

Answer 4

The macula is an avascular zone in the superior posterior region of the eye. Its center is the fovea, which is densely populated by cone cells and responsible for color vision.

Question 5

Sensation occurs when a physical stimuli is converted into a neural impulse. In terms of the human eye, what is the physical stimuli and what cells convert that into a neural impulse?

Answer 5

Light, a physical stimuli, enters the eye and is converted to a neural impulse by photoreceptor cells (rods & cones) present in the eye.

Question 6

How does the phototransduction cascade affect rod cells, the downstream bipolar and ganglion cells, and the optic nerve?

Answer 6

The phototransduction cascade deactivates rod cells that typically inhibit downstream cells. In response, a bipolar cell is activated, which activates a retinal ganglion cell that sends signals to the optic nerve, which finally leads to processing in the Brain.

Question 7

CRB Rods and Cones, in the absence of light, both release which neurotransmitter to inhibit the downstream bipolar cells?

(A) GABA
(B) Dopamine
(C) Glutamate
(D) Substance P

Answer 7

(C) Glutamate

Glutamate is released to inhibit downstream bipolar cells.

Question 8

When do on-center bipolar cells turn on? What about off-center bipolar cells?

Answer 8

On- and off-center refer to the status of a bipolar cell being either ON or OFF, and they are most activated when there’s a contrast between the lighting of the center and surroundings of their receptive fields (which contain many rods).

For an on-center bipolar cell, it is turned ON when light shines on the rods in the center of the receptive field (rods in the center turn off).

Off-center bipolar cells refer to bipolar cells being turned ON when light shines on the rods at the surroundings of the receptive field, not the rods in the center (rods in the center turned on). See image for more details.

Question 9

Describe the similarities between the Optic discs of rod and cone cells, and the presence of the protein, Opsin?

Answer 9

Both photoreceptor cells are composed of many layers of optic discs, which both contain a form of opsin (rods = rhodopsin/ cones = photopsin) to trigger the phototransduction cascade.

Question 10

How do the Parvo Pathway and Magno Pathway compare in terms of:

• Spatial Resolution (Detail)?
• Temporal Resolution (time)?
• Color Vision?

Answer 10

Spatial Resolution - The Parvo pathway can provide much greater detail, necessary for detecting form.

Temporal Resolution - The Magno Pathway has faster processing, necessary for tracking motion.

Color Vision - Only found in the Parvo Pathway.

Question 11

Arriving at the scene, an EMT needs to quickly assess the situation, including any bleeding, discoloration, injuries, etc. How does the parallel processing of multiple vision pathways enable them to do this quickly and efficiently?

Answer 11

The parallel processing of multiple pathways allows different aspects (color, form, motion) to be processed quickly at the same time, and integrated at higher vision centers.

Question 12

CRB Which of the following vision terms is best described as an inability to accommodate (focus light), usually caused by the loss of flexibility from the lens?

(A) Hyperopia
(B) Presbyopia
(C) Emmetropia
(D) Myopia

Answer 12

(B) Presbyopia

Presbyopia is an inability to accommodate (focus light) caused by the loss of flexibility of the lens. This commonly happens with aging.

Question 13

CRB Tyreke is a standout wide receiver, and has no issues with focusing light and tracking a football in the air. Which of the following vision terms is best described as normal vision, in terms of the ability to focus light?

(A) Hyperopia
(B) Presbyopia
(C) Emmetropia
(D) Myopia

Answer 13

(C) Emmetropia

Emmetropia refers to having normal vision and being able to focus light properly onto the retina.

Question 14

CRB Edith struggles to read on her computer screen, and often holds her laptop up very close to her face. Which of the following vision terms is commonly called “nearsightedness”, where the light converges too much and focuses before the retina?

(A) Hyperopia
(B) Presbyopia
(C) Emmetropia
(D) Myopia

Answer 14

(D) Myopia

Edith suffers from Myopia, or Nearsightedness, where the light focuses before striking the retina.

Question 15

CRB To treat hyperopia, a ___________ lens would be prescribed, whereas to treat myopia, a _________ lens would be prescribed.

Fill in the blanks using:

• Spherical
• Concave
• Convex
• Conical

Answer 15

Convex, Concave

To treat hyperopia, a Convex (converging) lens would be prescribed, whereas to treat myopia, a Concave (diverging) lens would be prescribed.

Question 16

Which part of the eye is thick fibrous tissue that is considered the white part of the eye and serves to protect the eye and is an attachment point for muscle so that one can move their eye in different directions?

(A) Cornea
(B) Retina
(C) Sclera
(D) Pupil

Answer 16

(C) Sclera

The Sclera is thick fibrous tissue that is considered the white part of the eye and serves to protect the eye and is also an attachment point for muscle so that one can move their eye in different directions.

Question 17

What structure of the eye is transparent and serves to protect the eye while bending incoming light?

(A) Pupil
(B) Cornea
(C) Iris
(D) Lens

Answer 17

(B) Cornea

The Cornea is a transparent structure in the front of the eye that serves to protect the eye while also bending some incoming light.

Question 18

Because the cornea is really sensitive it needs to be protected. The ___________ is a thin layer of epithelial cells that protects the cornea from friction and helps to moisturize the cornea as well.

(A) Iris
(B) Pupil
(C) Retina
(D) Conjunctiva

Answer 18

(D) Conjunctiva

The Conjunctiva is a thin layer of epithelial cells that protects the cornea from friction, such as when you rub your eyes, and also helps moisturize the cornea.

Question 19

The anterior chamber of the eye is filled with a water/salt substance, that provides nutrients to the cells of the cornea and iris. What is this water/salt substance known as?

(A) Vitreous Humor
(B) Lens
(C) Aqueous Humor
(D) Retina

Answer 19

(C) Aqueous Humor

The Aqueous Humor is water/salt substance that fills the anterior chamber of the eye and provides nutrients to supply the cornea and iris with.

Question 20

Which structure of the eye is composed of two different muscles that are responsible for adjusting the size of the pupil of the eye, and is also colored based on its pigmentation?

(A) Iris
(B) Cornea
(C) Lens
(D) Retina

Answer 20

(A) Iris

The Iris is composed of two different muscles that adjust the size of the pupil. The Iris is also the part of the eye that is colored and is responsible for a human having either blue/green/brown eyes.

Question 21

The opening or dark space in the middle of the eye, known as the pupil, adjusts its size based on the amount of light it receives. How does the pupil adjust its size in a dark environment? Light environment?

Answer 21

If it is dark outside, the pupil will expand to increase the amount of light able to enter the eye, while if it is light outside, the pupil will contract to decrease the amount of light able to enter the eye.

Question 22

What structure is found along the back of the eye, is filled with photoreceptor cells, and is the destination of light after it passes through the vitreous humor? This structure is responsible for converting light into a neural impulse that the brain can understand.

(A) Lens
(B) Sclera
(C) Retina
(D) Choroid

Answer 22

(C) Retina

The Retina lines the back of the eye and contains photoreceptor cells which upon receiving light convert the light into a neural impulse that the brain can understand.

Question 23

True or False? The retina sends information to the back of the eye through fibers that form the optic nerve, which ultimately leads to the brain for comprehension.

Answer 23

True. The retina sends information to the back of the eye through fibers that form the optic nerve, which ultimately leads to the brain for comprehension.

Question 24

Which membrane in the eye is right behind the retina and is a network of blood vessels that provides nutrients to retinal cells as well as other cells in the eye?

(A) Cornea
(B) Sclera
(C) Choroid
(D) Optic Nerve

Answer 24

(C) Choroid

The Choroid is a membrane in the eye that is right behind the retina and is a network of blood vessels that provides nutrients to retinal cells as well as other cells in the eye

Question 25

In terms of the difference of choroids, explain why cats have better night vision than humans?

Answer 25

In a human eye, the choroid is pigmented black. Thus when light enters the eye and passes the retina, the light is completely absorbed by the choroid. In cats, the choroid is shiny and thus if light is not absorbed by the retina and passes to the choroid, it is reflected back to the retina to be absorbed again, which enhances night vision.

Question 26

What is the difference in function between the rod cells and cone cells?

Answer 26

Rods are ultra-sensitive to light and simply detect light which is good for night vision. No color vision takes place in rod cells.

Cones are sensitive to color and thus responsible for color vision

Question 27

Which of the following are not a type of Cone?

(A) Red
(B) Blue
(C) Yellow
(D) Green

Answer 27

(C) Yellow

Cones come in 3 types: red, green, and blue.

Question 28

What is the relative density and location of the rod and cone cells in a human eye?

Answer 28

The cones are very densely populated and centered in the fovea, while scarcely present in the periphery of the retina.

The rods are densely populated in the periphery of the retina, but decline rapidly when approaching the fovea.

Question 29

There are approximately ____ million rod cells in the human eye. There are approximately ____ million cone cells in the human eye.

(A) 120, 120
(B) 120, 7
(C) 7, 7
(D) 7, 120

Answer 29

(B) 120, 7

There are approximately 120 million rod cells in the human eye. There are approximately 7 million cone cells in the human eye.

Question 30

Are Rod cells turned ON or OFF in the presence or absence of light?

Answer 30

Rod cells are turned ON in the absence of light.

Question 31

Put the following 5 steps of the phototransduction cascade in order:

I. The retinal goes from 11-cis to all trans, changes conformation of retinal and rhodopsin.
II. Sodium channels close without cGMP bound, rod hyperpolarizes, rod inactivated.
III. Light hits retinal in the rhodopsin (rod opsin).
IV. Transducin will break from rhodopsin, and the alpha subunit binds to Phosphodiesterase (PDE).
V. PDE converts cGMP->GMP.

(A) III > I > IV > V > II
(B) III > V > IV > I > II
(C) II > V > IV > I > III
(D) II > I > IV > V > III

Answer 31

(A) III > I > IV > V > II

The 5 steps of the phototransduction cascade in order:

Light hits retinal in the rhodopsin (rod opsin). > The retinal goes from 11-cis to all trans, changes conformation of retinal and rhodopsin. > Transducin will break from rhodopsin, and the alpha subunit binds to Phosphodiesterase (PDE). > PDE converts cGMP->GMP. > Sodium channels close without cGMP bound, rod hyperpolarizes and thus is inactivated.

Question 32

When you walk out from the bright sunlight into a dark room, you are unable to see at first, but after a few minutes your eyes adjust and you can begin to see clearly. What causes this on a molecular level?

Answer 32

Rods have slow recovery times. In the sunlight, the rods are hyperpolarized, allowing the bipolar cells to be activated. For rods, it takes a longer time than cones to return to the resting membrane potential and fire another action potential. Therefore, when you go into the dark room, it takes time for the rods to reactivate, and for one to see clearly in the dark room.

Question 33

True or False? Cones adapt to change in illumination very slowly, thus when one walks from a brightly lit room into a dimly light room, one is not able to clearly see color and can’t make the transition very quickly.

Answer 33

False. Cones adapt to change in illumination very QUICKLY, thus when one walks from a brightly lit room into a dimly light room, one is ABLE to clearly see color and the make the transition fairly quickly

Question 34

The part of the retina that is directly in front of where the optic nerve exits the eye is known as the _____________.

(A) Fovea
(B) Blind Spot
(C) Macula
(D) Optic Chiasm

Answer 34

(B) Blind Spot

The part of the retina that is directly in front of where the optic nerve exits the eye is known as the Blind Spot. The Blind Spot contains no rods or cones.

Question 35

There are no axons that run behind the cones in the fovea, creating an indentation. What is the functional purpose of this lack of axons?

Answer 35

With no nearby axons blocking the light, a higher resolution of light will hit the cones, giving more clarity of vision.

Question 36

A ray of light from the left visual field hits the ____________ side of the left eye and hits the __________ side of the right eye.

(A) Nasal, Temporal
(B) Temporal, Temporal
(C) Nasal, Nasal
(D) Temporal, Nasal

Answer 36

(A) Nasal, Temporal

A ray of light from the left visual field hits the Nasal side of the left eye and hits the Temporal side of the right eye.

Question 37

A ray of light from the right visual field hits the __________ side of the left eye and hits the _________ side of the right eye.

(A) Nasal, Temporal
(B) Temporal, Nasal
(C) Temporal, Temporal
(D) Nasal, Nasal

Answer 37

(B) Temporal, Nasal

A ray of light from the right visual field hits the Temporal side of the left eye and hits the Nasal side of the right eye.

Question 38

What is the point at which the optic nerve from each eye converges?

(A) Blind Spot
(B) Retina
(C) Optic Chiasm
(D) Visual Field

Answer 38

(C) Optic Chiasm

The Optic Chiasm is the point at which the optic nerve from each eye converges.

Question 39

At the optic chiasm, how are the nasal and temporal visual fields sorted? What purpose does this serve?

Answer 39

At the optic chiasm, light that hits the nasal visual field of each eye will cross over, while light that hits the temporal visual field will not cross over the optic chiasms.

This pathway of light from both the nasal and temporal visual fields allows light from the left visual field to be processed in the right side of the brain, while light from the right visual field to processed in the left side of the brain.

Question 40

If there is a lesion in the left optic nerve before the optic chiasm, how would vision be affected?

(A) All information from the right eye would be compromised.
(B) All information from the left eye would be compromised.
(C) All information from the right visual field would be compromised.
(D) All information from the left visual field would be compromised.

Answer 40

(B) All information from the left eye would be compromised.

With the lesion in the left optic nerve before the optic chiasm, all information from the left eye would be compromised

Question 41

If there is a lesion after the optic chiasm on the left side, how would vision be affected?

(A) All information from the right eye would be compromised.
(B) All information from the left eye would be compromised.
(C) All information from the right visual field would be compromised.
(D) All information from the left visual field would be compromised.

Answer 41

(C) All information from the right visual field would be compromised.

With a lesion after the optic chiasm on the left side, the information carried by the left optic nerve from the right visual field would be compromised

Question 42

When processing the environment, feature detection is known as breaking down an object to its component parts. What are these component parts?

(A) Color, Form,
(B) Motion, Form
(C) Color, Form, and Motion
(D) Color, Motion

Answer 42

(C) Color, Form, and Motion

Feature detection explains that when processing the environment, one makes sense of what they are looking at by breaking down an object into color, form, and motion.

Question 43

In terms of the Trichromatic theory of color vision, which of the following is the most accurate description?

(A) There are three types of rods, each most sensitive to a certain quantity/intensity of light.
(B) There are three types of cones, each most sensitive to a specific wavelength of light (Red, green, and blue).
(C) There are three types of cones, each most sensitive to a specific quantity/intensity of light.
(D) There are three types of rods, each most sensitive to a specific wavelength of light (Red, green, and blue).

Answer 43

(B) There are three types of cones, each most sensitive to a specific wavelength of light (Red, green, and blue).

The RGB cones are most sensitive to that type of light, and the combination of the stimulation of each cone types codes for color vision

Question 44

The Parvo Pathway is __________ detecting while the Magno Pathway is __________ detecting.

(A) Form, Form
(B) Form, Motion
(C) Motion, Form
(D) Motion, Motion

Answer 44

(B) Form, Motion

The Parvo Pathway is Form detecting and the Magno Pathway is Motion detecting.

Question 45

CRB Little Tommy was doing really well catching fly balls in the outfield, but struggled to see the ball when his coach was standing a few feet away and tossing it to him. Which of the following vision terms is commonly called “farsightedness”, where the light is not converging enough and would focus behind the retina?

(A) Hyperopia
(B) Presbyopia
(C) Emmetropia
(D) Myopia

Answer 45

(A) Hyperopia

Little Tomnmy suffers from Hyperopia, or Farsightedness, in which light does not converge quick enough and would focus behind the retina.

Question 46

In terms of light being present or not, when is the Phototransduction cascade triggered?

Answer 46

In the presence of light, the Phototransduction cascade is triggered and takes place in rod cells, cone cells and photosensitive ganglion cells.