Vision

What are the two rules of visual acuity?

1. Near objects focal points are always more posterior that far object focal points 2. Accommodation moves all focal points anteriorly

When performing the visual acuity test using the Snellen eye chart, how far away from the chart does the subject stand? ______ feet. What number is considered normal vision? ________.

20, 20/20

To keep an object in focus when the object is near the eye, the ciliary body muscles change the shape of the lens. This process is called ______.

Accommodation

__________ is the ability of eye to focus on near objects.

Accommodation

Explain briefly how you performed the near point of accommodation test.

An object (such as a pen) was slower brought closer and closer to the test sunject's eye. A ruler was used to measure the closest distance that the subject could keep the object in focus.

A defect (a non-smooth area) in the lens or the cornea that causes one part of the field of vision to be blurry is called a(n) ____________.

Astigmatism

_____ is a problem in which the cornea or lens is unevenly shaped, so that some objects appear blurry but others are in focus.

Astigmatism

If a person with hyperopia is looking at a far object and their ciliary body is relaxed, the focal point of the object will fall in front of/on/behind (circle one of the three) the retina.

Behind

44. 20/15 vision is better/worse (circle one) than 20/20 vision.

Better

What do rods detect?

Black and white

The area of the eye where the optic nerve passes through the retina is called the _______.

Blind spot

The region of the retina where the axons of the retinal ganglion cells leave the eye is called the _____ or _____, and lacks _____.

Blind spot, Optic disk, Photoreceptor cells

The choroid coat of the eye contains what two structures/substances?

Blood vessels, Light-absorbing pigments

The middle tunic of the eye is called the __________

Choroid coat

Define middle tunic

Choroid coat, Mostly blood vessels and dark pigments

Accommodation occurs when the _______ bends the ______ into a different shape.

Ciliary body, Lens

When a far object is sharply focused on the retina the

Ciliary muscle is relaxe

What do cones detect?

Color (red, blue, green)

The photoreceptors known as cones allow for

Color vision

Color blindness is due to the genetic absence of one type of _____.

Cone types

What are the two major types of photoreceptors called?

Cones and rods

The _______ are the photoreceptors that provide color vision and the ________ are the photoreceptors that provide black-and-white vision.

Cones, Rods

Define accommodation

Contraction of ciliary body muscles to change lens shape to move focal points anteriorly to focus on near objects

The outermost tunic of the eyeball has two regions: In the front, it is clear, forming the _____. The other areas are white, and form the _____.

Cornea, Sclera

What do photoreceptors do?

Detect light and transducer it inside into a nerve signal

In dimly lit areas, the pupil will dilate/contract

Dilate

What are the types of vision?

Emmetropia, Hyperopia, Myopia, Presbyopia, Astigmation

The outer muscles on the eye are called the _______ muscles. They are skeletal muscles that control voluntary eye movements such as looking left, looking right, etc.

External

Define presbyopia (old vision)

Eye can focus on far objects but not near objects because the lens has become hard and inflexible (progressive)

Define myopia (near-sighted)

Eye can focus on near objects but not far objects because the lens shape has changed such that all focal points are abnormally anterior

In a relaxed eye, the lens focuses far/near (circle one) objects on the retina.

Far

Where are the far and near focal points if the CB is relaxed and has Hyperopia?

Far: Behind retina, Near: Way Behind retina

Where are the far and near focal points if the CB is relaxed and has Myopia?

Far: In front of retina, Near: On retina

Where are the far and near focal points if the CB is contracted and has Emmetropia?

Far: In front retina, Near: On retina

Where are the far and near focal points if the CB is contracted and has Hyperopia?

Far: On retina, Near: Behind retina

Where are the far and near focal points if the CB is relaxed and has Emmetropia?

Far: On retina, Near: Behind retina

Where are the far and near focal points if the CB is contracted and has Myopia?

Far: Way in front of retina, Near: In front of retina

The optic nerve is composed of axons extending from the ____ cells in the retina

Ganglion

In order to be absorbed by photoreceptors, light must actually pass through the _____ layer and the ____ layer of the retina.

Ganglion cell, Bipolar cell

The retina has three sub-layers. The cells of the three layers (from anterior-most to posterior-most) are called ______, _______, and _______.

Ganglion cells, Bipolar cells, Photoreceptor cells

The retina has three layers of nervous tissue. Which is the correct order of the retina's layers, from anterior to posterior?

Ganglion cells, Bipolar cells, Photoreceptors

Astigmatism is caused by a defect (non-smooth area) in the ______ or the __

Lens, Cornea

Color blindness is more common in which sex?

Males

The visual disorder where near objects can be focused but far objects can't is sometimes called "near sighted", but the correct term for the condition is ______.

Myopia

_____ is nearsightedness: All focal points are anterior/posterior (circle one) compared to where they normally are found.

Mypoia, Anterior (forward)

Contracting the ciliary body of an eye results in focusing far/near (circle one) objects on the retina.

Near

Name the test you performed in lab to measure how close an object could be and still be focused.

Near point accommodation

When a visual pigment molecule in a photoreceptor cell is hit by light, this results in the photoreceptor cell generating a _______.

Nerve signal

Define Emmetropia

Normal vision (far objects and near objects can be focused)

If a person with hyperopia is looking at a far object and their ciliary body is contracted, the focal point of the object will fall in front of/on/behind (circle one of the three) the retina.

On

If a person with myopia is looking at a near object and their ciliary body is relaxed, the focal point of the object will fall in front of/on/behind (circle one of the three) the retina.

On

The axons of the retinal ganglion cells run along the surface of the retina then they become bundled together, pass through the back of the eye, and connect to the brain. This bundle of axons is called the _____.

Optic nerve

The function of the lens of the eye is to

Serve as the major site of focusing of light rays

Each eye has how many extrinsic (external) muscles to move the eyeball? ______

Six

Define ciliary body

Smooth muscle attached to the lens for accommodation

Describe lens

Soft gel material, Flexible

What do the numbers 20/30 mean for visual acuity?

The 20 is the distance that the patient stood from and the 30 is the distance an average person could read that line

Define Visual acuity

The ability of the eye to form sharp in-focus images

Define Accommodation

The ciliary body muscles changing the shape of the lens to move all focal ​points forward to focus on near objects

Describe how, in the normal functioning of the eye, the shape of the lens is changed, and use this information to explain how images are kept in focus on the retina as a distant object is brought closer to the eyes.

The ciliary body muscles, which surround the lens of the eye, can change the shape of the lens. When a person is looking at a far object, the ciliary body muscles are relaxed and the lens' shape is such that it focuses far object onto the retina. When a person looks at a near object, the ciliary body muscles contract. This changes the shape of the lens such that near objects are focused onto the retina

What makes up the outer tunic?

The cornea and the sclera

The eye wall is composed of three layers, which are called "_____."

Tunics

The wall of the eye has three layers called _______.

Tunics

What is the name of the "letters chart"?

Visual acuity test using the Snellen eye chart

Define Adaptation

When a sense organ stops responding to a stimulus when it has been over ​stimulated by that stimulus

Describe Sclera

White dense connective tissue

Define pupil

Hole to let light into the eye

The vision problem __________ occurs when the focal point of the lens is deeper than (behind) the retina.

Hyperopia

The visual disorder where far objects can be focused but near objects can't is sometimes called "far sighted", but the correct term for the condition is ______.

Hyperopia

Which disorder (hyperopia or myopia) is the one where the person can see far objects but not near objects?

Hyperopia

____ is farsightedness: all focal points are anterior/posterior (circle one) compared to where they normally are found.

Hyperopia, Posterior (deep)

If a person with myopia is looking at a far object and their ciliary body is relaxed, the focal point of the object will fall in front of/on/behind (circle one of the three) the retina

In front of

If a person with myopia is looking at a near object and their ciliary body is contracted, the focal point of the object will fall in front of/on/behind (circle one of the three) the retina.

In front of

Explain the reason for blurred vision in a person with myopia, and describe how this person's vision is improved by the lenses in a pair of glasses.

In myopia, the shape of the lens has changed such that the focal points of all objects are abnormally forward in the eye. To correct this problem, glasses (or contact lenses) are worn that move all focal points backward

The colorful part of the eye (the part that can be brown, blue, gray, or green) is called the ______.

Iris

In the front of the eye, the _______ is the pigmented area surrounding the pupil. Its purpose is to _________.

Iris, Control the size of the pupil (to regulate the amount of light entering the eye)

The _____ is the clear part of the eye that focuses light images on the retina. Many patients benefit from having it re-shaped with a laser to correct myopia, hyperopia, or astigmatism.

Lens

The retina generates a nerve signal when it is struck by light. Use the numbers 1 - 5 to indicate in what order the nerve signal passes through the following structures: ​Optic nerve: ____​ ​Ganglion cell: ____​ ​Visual area of cerebrum: ___ ​Photoreceptor cell: ____​ ​Bipolar cell: ____

Optic nerve = 4 ​Ganglion cell = 3 ​Visual area of cerebrum = 5 ​Photoreceptor cell = 1 ​Bipolar cell = 2

Define astigmatism

Parts of the field of vision are in focus but other parts are out of focus due to a defeat (non-smooth region) on lens or cornea

Rods and cones are sensory cells that respond to light. Together, they are called _____ cells.

Photoreceptor

_____ are neurons that sense light energy; they are found in the retina.

Photoreceptor cells

What cells make up the retina?

Photoreceptor cells, Bipolar cells, and Ganglion cells

Define iris

Pigmented smooth muscle that controls the size of the pupil

Light enters the interior of the eye through a small hole called the ______.

Pupil

If you stare at a blue-green colored dot for 30 seconds and then look at a white piece of paper, you will see a colorful after-image of the dot​ a) What color will the after-image be?

Red

What are the three types of color-sensing photoreceptors (what colors)? ____, ____, and ____.

Red, Blue, Green

In innermost tunic contains the sensory neurons that transduce light into nerve signals. This tunic is called the _______.

Retina

The _____ is the innermost tunic of the three eye wall tunics.

Retina

Define inner tunic

Retina/Nervous tissue, Detects light and transducers light into nerve signals

What are the two types of photoreceptor cells?

Rods and cones

What do the external eye muscles do? In what ways are they different from the other eye muscles (the iris and the ciliary body)?

The external eye muscles move the eye up, down, left, right, and diagonally. In other words, they control what direction the eye is looking. They are different from the eye muscles of the iris and ciliary body in that the external muscles are skeletal (voluntary) mucles, whereas the iris and ciliary body muscles are smooth (involuntary) muscles

Define emmetropia (normal vision)

The eye can focus on far objects and near by accommodation

Define hyperopia (far-sighted)

The eye can focus on far objects but not on near objects because the lens shape has changed such that all focal points are abnormally posterior

Define visual acuity

The eyes ability to form a sharp in-focus image

Which muscles of the eye are smooth muscles?

The iris and the ciliary body are smooth muscles. (The external eye muscles are skeletal muscles, not smooth muscles)

Within the retina

The photoreceptors synapse directly with the bipolar cells

If you stare at a blue-green colored dot for 30 seconds and then look at a white piece of paper, you will see a colorful after-image of the dot. b) Explain briefly (2-3 sentences) what causes this phenomena:

There are three cone types of photoreceptor cells in the retina: Blue, green, and red. If a person stares at a blue-green dot for a long period of time, the blue and green cones undergo "adaptation, " which means they temporarily stop responding to the stimulus they normally detect (blue and green light, in this case). When the person starts to look at a white piece of paper (which normally stimulates all three cones types) the blue and green cones are not stimulated (because they are still undergoing adaptation). The only cones that respond, therefore, are the red cones. This produces a red after image of the dot

Explain (in two or three sentences) what is the anatomical reason that we have a blind spot. In other words, what is at that spot instead of light-detecting cells?

There are three layers of neurons in the retina of the eye. The ganglion cells are the last group of neurons in the retina to receive the nerve signal when light is detected. The axons of the ganglion cells bundle together and then the bundle of axons (which is the optic nerve) passes through the back wall of the eye. At the location where the optic nerve passes through the back of the eye, the nerve takes up all the room so there is no room left for photoreceptor cells, and therefore no light can be detected at that location of the retina.