Sensory system structures of the eye
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Sensory System structures of the eye. The Five Senses. Eyes Sight Ears Hearing Nose Smell Tongue Taste Skin Touch. Eyes. THE EYE 1” in diameter Protected by: orbital socket eyebrows eyelashes eyelids. Structures of the eyes. External structures Orbit Eyelids

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Sensory System structures of the eye

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Sensory system structures of the eye

Sensory System structures of the eye


The five senses

The Five Senses

  • Eyes

    • Sight

  • Ears

    • Hearing

  • Nose

    • Smell

  • Tongue

    • Taste

  • Skin

    • Touch

3.03 Remember the structures of the sensory system


Sensory system structures of the eye

Eyes

3.03 Remember the structures of the sensory system


Sensory system structures of the eye

  • THE EYE

  • 1” in diameter

    Protected by:

  • orbital socket

  • eyebrows

  • eyelashes

  • eyelids


Structures of the eyes

Structures of the eyes

  • External structures

    • Orbit

    • Eyelids

    • Eyelashes

    • Conjunctiva

    • Lacrimal apparatus

    • Extrinsic muscles

3.03 Remember the structures of the sensory system


Structures of the eyes1

Structures of the eyes

Let’s look at the external structures


Sensory system structures of the eye

conjunctiva

A thin membrane that lines the eyelids and covers part of the eye. It secretes mucus to lubricate our eyes.

  • Wall of the eye made up of three “coats”

http://www.stlukeseye.com/popups/images/Conjunctiva.jpg


Sensory system structures of the eye

SCLERA

  • Outer layer

  • White of the eye

  • Tough coating, helps

    maintain shape of the eye and protects what’s inside.

  • Muscles responsible for moving the eyeare attached to the sclera – called EXTRINSIC MUSCLES

http://www.cis.rit.edu/people/faculty/montag/vandplite/images/chapter_8/cornea2.jpg


Structures of eyes

Structures of eyes

Extrinsic muscles

3.03 Remember the structures of the sensory system


Sensory system structures of the eye

  • ANTERIOR CHAMBER filled with AQUEOUS HUMOR, a watery fluid.

  • POSTERIOR CHAMBER filled with transparent, jellylike substance – VITREOUS HUMOR

*

*


Sensory system structures of the eye

CORNEA

  • Front of sclera – clear part (NOblood vessels)

  • Transparent so light rays can pass through

  • Gets oxygen and nutrients through our lymph fluid.


Sensory system structures of the eye

  • CHOROID COAT

  • Middle layer

  • Contains blood vessels

  • Opening in front is the pupil.

  • Colored, muscular layer surrounding the pupil is called the IRIS.

  • INTRINSIC MUSCLES – change size of the iris to control amount of light entering the pupil.

http://stlukes-eye.com/popups/images/Choroid.jpg


Sensory system structures of the eye

LENS

LENS

  • Crystalline structure located behind the iris and pupil.

  • Elastic

  • Disc shaped

  • biconvex

  • Situated between the anterior and posterior chambers

http://www.visionweb.com/vwweb/images/content/consumers/illustrations/about_the_eye_anatomy_lens2.jpg


Sensory system structures of the eye

RETINA

  • Innermost layer

  • Light rays focus an image on the retina

  • The image travels to the cerebral cortex via the OPTIC NERVE

  • If light rays don’t focus properly on the retina, corrective lenses can bend the light rays as required.

  • Retina contains specialized cells called rods and cones

http://www.thetech.org/exhibits/online/color/eye/Rods_and.gif


Sensory system structures of the eye

Eyes

  • Let’s look at the internal structures

3.03 Remember the structures of the sensory system


Structures of the eyes2

Structures of the eyes

  • Rods and cones

    • Rods

      • Activate in dim light

      • Do not perceive color

    • Cones

      • Activate in bright light

      • Perceive color


Sensory system structures of the eye

OPTIC DISC

A spot on the retina, known as the “blind spot” – nerve fibers gather here to form the optic nerve. Does not contain any rods or cones.


Sensory system structures of the eye

Cornea

Pupil

Lens

(Where light rays are refracted)

Retina

Rods & Cones(pick up stimulus)

Optic

Nerve


Eye trivia

Eye Trivia

What gives the

iris color?

Which famous screen actress was noted for her stunning eyes?

Many people thought her irises were violet in color…

3.03 Remember the structures of the sensory system


Sensory system structures of the eye

Eyes

Name the structures…

sclera

Ciliary body

Ch…..

conjunctiva

Re….

cornea

iris

pupil

lens

Anterior chamber

optic nerve

Optic d…

Extrinsic muscle

Review

3.03 Remember the structures of the sensory system


3 04 functions and disorders of the eye

3.04 Functions and disorders of the eye

3.04 Understand the functions and disorders of the sensory system


Understanding the functions of the eye

Understanding the functions of the eye

Sight

3.04 Understand the functions and disorders of the sensory system


Understanding the functions of the eye1

Understanding the functions of the eye

Interesting

tidbit

External eye

  • Orbit

  • Eyelids and eyelashes

    Women blink twice as often as men. Why do we blink?

  • Conjunctiva

  • Lacrimal apparatus - The system that secretes and drains tears into the nasal cavity, consisting of the lacrimal gland, the lacrimal lake, the lacrimal duct, the lacrimal sac, and the nasolacrimal duct.

  • Extrinsic muscles

3.04 Understand the functions and disorders of the sensory system


Sensory system structures of the eye

The eye is bathed in fluid from our lacrimal glands. The tears empty into our nasal cavity. This is why your nose gets stuffy when you cry!!

http://medicalimages.allrefer.com/large/lacrimal-gland-anatomy.jpg


Understanding the functions of the eye2

Understanding the functions of the eye

Which extrinsic muscle allows you to look upward?

External eye

Extrinsic muscles

are voluntary muscles, external to the eye, that control the direction of the eye movement.

3.04 Understand the functions and disorders of the sensory system


Understanding the functions of the eye3

Understanding the functions of the eye

Internal eye

  • Cornea

  • Iris

  • Pupil

3.04 Understand the functions and disorders of the sensory system


Understanding the functions of the eye4

Understanding the functions of the eye

Internal eye

  • Ciliary body- is the structure in the eye that releases a transparent liquid called the aqueous humor within the eye.

  • Lens

3.04 Understand the functions and disorders of the sensory system


Understanding the functions of the eye5

Understanding the functions of the eye

Internal eye

  • Sclera

  • Choroid

  • Retina

3.04 Understand the functions and disorders of the sensory system


Understanding the functions of the eye6

Understanding the functions of the eye

Internal eye

  • Vitreous humor = clear gel that fills the space between the lens and the retina of the eyeball

3.04 Understand the functions and disorders of the sensory system


Sensory system structures of the eye

It is a small and highly sensitive part of the retina. It allows us to appreciate detail and perform tasks that require central vision such reading.

What is the macula?

3.04 Understand the functions and disorders of the sensory system


Understanding the functions of the eye7

Understanding the functions of the eye

  • Trace the pathway of vision.

  • Is there anything strange about this picture? Explain

3.04 Understand the functions and disorders of the sensory system


Understanding the functions of the eye8

Understanding the functions of the eye

Vision

What happens as you move your paper away from and

toward to your eye?

3.04 Understand the functions and disorders of the sensory system


Sensory system structures of the eye

Check your knowledge!

3.04 Understand the functions and disorders of the sensory system


Disorders of the eye

Disorders of the eye

Astigmatism

Presbyopia

Glaucoma

Diabeticretinopathy

Detachedretina

Hyperopia

Color blindness

Cataract

Myopia

Conjunctivitis

Have you heard of these conditions?

What do you know about them?

3.04 Understand the functions and disorders of the sensory system


Disorders of the eye1

Disorders of the eye

Cataract

Describe this lens.

3.04 Understand the functions and disorders of the sensory system


Disorders of the eye2

Disorders of the eye

Cataract

How is a cataract treated? Initially treated with new glasses or improved lighting. Surgical removal required with progression.

3.04 Understand the functions and disorders of the sensory system


Disorders of the eye3

Disorders of the eye

Ishihara chart

Color blindness

Do you see the number?

What is color blindness?

What causes it?

Who is most likely to have color blindness?

3.04 Understand the functions and disorders of the sensory system


Sensory system structures of the eye

Color blindness occurs when there is a problem with the nerve cells of the eye called cones.

Most color blindness is due to a genetic problem.

About 1 in 10 men have some form of color blindness. Very few women are color blind.

3.04 Understand the functions and disorders of the sensory system


Disorders of the eye4

Disorders of the eye

How is conjunctivitis spread?

How can it be prevented?

Conjunctivitis

  • What is conjunctivitis?

  • What are the symptoms?

  • What causes it?

  • How is it treated?

3.04 Understand the functions and disorders of the sensory system


Conjunctivitis

Conjunctivitis

inflammation or infection of the membrane lining the eyelids - the conjunctiva.

There are many causes of conjunctivitis.

Viruses are the most common cause.

"Pink eye" refers to a viral infection of the conjunctiva. These infections are especially contagious among children.

Practice good hand washing!!!!!!!

Tx = Antibiotic eye drops if bacterial conjunctivitis. Viral conjunctivitis will disappear on its own. Doctors may give a mild antibiotic eye drop for “pink eye” to prevent bacterial conjunctivitis.


Detached retina

Detached retina

Retinal detachment often begins when the vitreous gel shrinks and separates from the retina allowing fluid to seep behind the retina causing it to detach.

Retinal detachment requires care right away. Without treatment, vision loss can progress from minor to severe or even to blindness within a few hours or days.

Surgery is the only way to reattach the retina. In most cases, surgery can restore good vision.

3.04 Understand the functions and disorders of the sensory system


Sensory system structures of the eye

Detached retina

Compare this process to the previous picture.

What might cause this condition?

3.04 Understand the functions and disorders of the sensory system


Causes of retinal detachment

Causes of retinal detachment:

An eye or head injury leading to tears or holes in the retina.

Traction on the retina. Traction pulls the retina away from the layers beneath it. The most common cause of this problem is diabetes.

3.04 Understand the functions and disorders of the sensory system


Disorders of the eye5

Disorders of the eye

Diabetic retinopathy

  • What causes diabetic retinopathy?

  • What are the symptoms?

  • Explain the impact on vision.

3.04 Understand the functions and disorders of the sensory system


Diabetic retinopathy

Diabetic retinopathy

Diabetes damages the small blood vessels in your retina. This is called diabetic retinopathy.

leading cause of blindness in working-age Americans.

People with type 1 and type 2 diabetes are at risk for this condition.

3.04 Understand the functions and disorders of the sensory system


What are the symptoms

What are the symptoms?

Most often, diabetic retinopathy has no symptoms until the damage to your eyes is severe.

  • Blurred vision and slow vision loss over time

  • Floaters and shadows

  • Trouble seeing at night

3.04 Understand the functions and disorders of the sensory system


Treatments for diabetic retinopathy

Treatments for diabetic retinopathy

Laser eye surgery creates small burns in the retina where there are abnormal blood vessels.

A surgical procedure called vitrectomy is used when there is bleeding (hemorrhage) into the eye.

Drugs that prevent abnormal blood vessels from growing, and steroid drugs injected into the eyeball are possible new treatments for diabetic retinopathy.

3.04 Understand the functions and disorders of the sensory system


Disorders of the eye6

Disorders of the eye

Tonometry

Glaucoma

  • What are the common symptoms of glaucoma?

  • How is it diagnosed?

  • How is it treated?

3.04 Understand the functions and disorders of the sensory system


Glaucoma

Glaucoma

Glaucoma refers to a group of eye conditions that lead to damage to the optic nerve. This nerve carries visual information from the eye to the brain.

In most cases, damage to the optic nerve is due to increased pressure in the eye, also known as intraocular pressure (IOP).

3.04 Understand the functions and disorders of the sensory system


Causes incidence and risk factors

Causes, incidence, and risk factors

Glaucoma is the second most common cause of blindness in the United States. There are four major types of glaucoma:


Sensory system structures of the eye

Open-angle glaucoma is the most common type.

The cause is unknown.

Most people have no symptoms

There is a slow loss of peripheral vision

Runs in families.

People of African descent are at particularly high risk for this disease.


Sensory system structures of the eye

The front part of the eye is filled with a clear fluid called aqueous humor. This fluid is constantly being reproduced. It leaves the eye through channels in the front.

Anything that slows or blocks the flow of this fluid will cause pressure to build up in the eye and causes damage to the optic nerve.


Treatment for glaucoma

Treatment for Glaucoma

Acute angle-closure attack is a medical emergency. Blindness will occur in a few days if it is not treated. If you have angle-closure glaucoma, you will receive:

Eye drops

Medicines to lower eye pressure, given by mouth and by IV

Some people also need an emergency operation, called an iridotomy. This procedure uses a laser to open a new pathway in the colored part of the eye. This relieves pressure and prevents another attack.

3.04 Understand the functions and disorders of the sensory system


Disorders of the eye7

Disorders of the eye

Macular degeneration

What is macular degeneration? What do these pictures represent?

Compare the two types.

How is it diagnosed?

What is the treatment?

3.04 Understand the functions and disorders of the sensory system


Macular degeneration

Macular Degeneration

Macular degeneration is the leading cause of severe vision loss in people over age 60. It occurs when the small central portion of the retina, known as the macula, deteriorates. The retina is the light-sensing nerve tissue at the back of the eye. Because the disease develops as a person ages, it is often referred to as age-related macular degeneration (AMD). Although macular degeneration is almost never a totally blinding condition, it can be a source of significant visual disability. There are two types: dry and wet

3.04 Understand the functions and disorders of the sensory system


Dry vs wet macular degeneration

Dry vs Wet Macular Degeneration

dry

wet

Wet macular degeneration occurs when abnormal blood vessels grow behind the macula. These vessels are fragile and leak blood, resulting in scarring of the macula. Straight-ahead vision can become distorted or lost entirely in a short period of time.  Accounts for approximately 10% of the cases, but results in 90% of the legal blindness.

  • Dry macular degeneration, in which the cells of the macula slowly begin to break down, resulting in loss of clear, straight-ahead vision. It is diagnosed in 90 percent of the cases.


Treatments

Treatments

Many researchers believe that certain nutrients — zinc, lutein and vitamins A, C and E — help lower the risk or slow down the progression of dry macular degeneration.

  • Treatments for macular degeneration depend on whether the disease is in its early-stage, dry form or in the more advanced, wet form that can lead to serious vision loss. No FDA-approved treatments exist yet for dry macular degeneration, although nutritional intervention may help prevent its progression to the wet form.

3.04 Understand the functions and disorders of the sensory system


Sensory system structures of the eye

Problems with Focus

Compare the symptoms and treatments of these common eye disorders.

Can a person have more than one of these disorders? Explain.

3.04 Understand the functions and disorders of the sensory system


Nearsightedness

Nearsightedness

  • Nearsightedness = myopiaNearsightedness can develop early in life or in adulthood, and is caused by the eyeball becoming oval or egg-shaped instead of round. When this happens, light entering the eye's lens does not reach the retina at the back of the eyeball, but focuses just ahead of it. The result is blurred vision.


Farsightedness

Farsightedness

Farsightedness is a common eye problem. Typically, it is caused by the ball of the eye being too short, so that the lens focuses an image behind the retina. Often, children who suffer from farsightedness outgrow it. People with farsightedness can focus on objects that are far away, but can't bring objects closer to them into focus.  The official medical term is hyperopia.  

3.04 Understand the functions and disorders of the sensory system


Astigmatism

Astigmatism

People are able to see because the front part of the cornea is able to bend (refract) light and focus it onto the back surface of the eye, called the retina.

 If the light rays are not clearly focused on the retina, the images you see may be blurry.

With astigmatism, the cornea is abnormally curved, causing vision to be out of focus.

The cause of astigmatism is unknown. It is usually present from birth, and often occurs together with nearsightedness or farsightedness.

Astigmatism is very common.

Glasses or contact lenses will correct astigmatism, but do not cure it.


Presbyopia

Presbyopia

In the young eye, the lens needs to change its length or shape to focus on objects that are close. The ability of the lens to change shape is called the elasticity of the lens. This elasticity is slowly lost as people age. The result is a slow decrease in the ability of the eye to focus on nearby objects. 

People usually notice the condition at around age 45. Presbyopia is a natural part of the aging process and it affects everyone.

Bifocals are the answer to this vision defect!

3.04 Understand the functions and disorders of the sensory system


Testing vision

Testing vision

What is the difference between

an ophthalmologist and an optician?

How do we test visual acuity? A Snellen chart is an eye chart used to measure visual acuity.

What is 20/20?

What does PERRLA mean? PERRLA = Pupils Equal, Round, Reactive to Light and Accommodation

3.04 Understand the functions and disorders of the sensory system


What is 20 20 vision

What is 20/20 vision?

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.


3 04 functions and disorders of the eye1

3.04 Functions and disorders of the eye

The End

3.04 Understand the functions and disorders of the sensory system


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