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Transcript of The Special Senses (Eye and Ear) CHAPTER 14. 2 Overview of the Eye Eye acts much like a camera...
![Page 1: The Special Senses (Eye and Ear) CHAPTER 14. 2 Overview of the Eye Eye acts much like a camera –Lens of eye adjusts to bring object into focus –Pupil.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649db55503460f94aa703f/html5/thumbnails/1.jpg)
The Special Senses(Eye and Ear)
CHAPTER 14
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Overview of the Eye
• Eye acts much like a camera– Lens of eye adjusts to bring object into focus– Pupil of eye constricts to allow less light to
enter in bright setting or dilates to allow more light to enter in darker setting
– Through bending of light rays, image reaches retina
• Sensitive nerve cell layer of eye• Image is transmitted to brain for interpretation
![Page 3: The Special Senses (Eye and Ear) CHAPTER 14. 2 Overview of the Eye Eye acts much like a camera –Lens of eye adjusts to bring object into focus –Pupil.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649db55503460f94aa703f/html5/thumbnails/3.jpg)
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• Sclera– White portion of eye
• Tough, fibrous membrane• Maintains shape of eyeball• Serves as protective covering for eye
• Iris– Colored portion of eye
• Pupil– Opening in center of eye– Controls amount of light entering eye
Structures of the Eye(Front View)
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• Conjunctiva– Thin mucous membrane layer that lines anterior part
of eye and inner part of eyelids• Colorless, but appears white because it covers sclera
• Lacrimal gland– Located at upper outer edge of each eye
• Produces tears
• Lacrimal duct– Located at inner edge of eye
• Tears drain from eye through this duct
Structures of the Eye(Front View)
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Structures of the Eye(Front View)
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• Eyelids– Continuous with skin and cover the eyeball– Keep surface of eyeball lubricated and protected from
dust and debris through blinking motion
• Eyelashes– Located along edges of eyelids– Help protect eyeball by preventing foreign materials
and/or insects from coming in contact with surface of eyeball
Structures of the Eye(Front View)
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Structures of the Eye(Cross Section)
• Sclera– “White of the eye”– Thinnest over anterior surface of the eye– Thickest at the back of the eye, near opening
for optic nerve
• Cornea– Continuous with anterior portion of sclera– Transparent, nonvascular layer covering
colored part of the eye
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• Conjunctiva– Mucous membrane lining inner surfaces of
eyelids and outer surfaces of eye
• Choroid– Vascular middle layer of eye
• Just beneath sclera• Contains extensive capillaries that provide blood
supply and nutrients to eye• Contains the iris, ciliary body, and suspensory
ligaments
Structures of the Eye(Cross Section)
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• Iris– Colored portion of eye
• Can be seen through transparent corneal layer
• Pupil– Located in center of iris
• Controls amount of light entering eye
• Lens– Colorless biconvex structure that aids in
focusing images clearly on retina
Structures of the Eye(Cross Section)
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• Ciliary body– Located on each side of the lens– Contains muscles responsible for adjusting lens to
view near objects
• Suspensory ligaments– Radiate from ciliary body and attach to lens– Hold lens in place– Assist in adjusting shape of lens for proper focusing of
eye
Structures of the Eye(Cross Section)
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• Retina– Sensitive nerve cell layer
• Changes energy of light rays into nerve impulses• Transmits nerve impulses via optic nerve to brain
for interpretation of image seen by eye
– Nerve cells of retina• Rods are responsible for vision in dim light and for
peripheral vision• Cones responsible for visualizing colors, central
vision, and vision in bright light
Structures of the Eye(Cross Section)
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• Retina – Macula Lutea
• Oval, yellowish spot near center of retina
– Fovea Centralis• Small depression located within macula lutea• Sharpest image is obtained when image focuses
directly on fovea centralis = central vision
Structures of the Eye(Cross Section)
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• Optic nerve– Receives impulses from retina and transmits
them to the brain• Images are then interpreted as vision
• Optic disc– Contains no rods or cones– Known as the “blind spot” of the eye– Center of optic disc serves as point of entry
for artery that supplies retina
Structures of the Eye(Cross Section)
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Structures of the Eye(Cross Section)
Lateral Cross Section of the Eye
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• Anterior cavity of the eye– Anterior chamber
• Located in front of lens• Filled with clear, watery fluid called aqueous humor
– Posterior chamber• Located behind lens• Also filled with aqueous humor • Flows back and forth between both chambers
Structures of the Eye(Cross Section)
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• Posterior cavity of eye– Posterior to lens– Filled with vitreous humor
• Clear, jellylike substance that gives shape to the eyeball
• Not constantly reproduced• Blindness can result if vitreous humor escapes
from eye
Structures of the Eye(Cross Section)
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Process of Vision
• Process begins as light rays enter eye– Transmitted through cornea, aqueous humor,
pupil, lens, and vitreous humor to retina• Sensitive nerve cells of retina transmit image
through optic nerve to brain• Brain interprets image as vision
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Process of Vision• Refraction
– Process of bending of light rays as they pass through the various structures of the eye to produce a clear image on the retina
• Errors of refraction – Occur when eyeball is abnormally shaped– Occur when lens has lost ability to
accommodate to near vision• Vision will be blurred• Can be adjusted with corrective lenses
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PATHOLOGICAL CONDITIONS
The Eye
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Astigmatism
• Pronounced– (ah-STIG-mah-tizm)
• Defined– Refractive error causing light rays entering the
eye to be focused irregularly on the retina due to an abnormally shaped cornea
• Correction: contact lenses or eyeglasses to neutralize defect
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Blepharitis
• Pronounced– (blef-ah-RYE-tis)
• Defined– Inflammation of the eyelid margins stemming
from seborrheic, allergic, or bacterial origin
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Blepharoptosis(Ptosis)
• Pronounced– (blef-ah-roh-TOH-sis)
• Defined– Occurs when eyelid partially or entirely covers
the eye as a result of a weakened muscle
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Blepharoptosis
Blepharoptosis
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Blindness
• Pronounced– (BLINDNESS)
• Defined– Absence of vision or the need for assistive
devices and/or assistance from others to accomplish daily activities due to inability to see
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Monochromatism (Color Blindness) • Pronounced
– (mon-oh-KROH-mah-tizm)
• Defined– Inability to sharply perceive visual colors
• Daltonism– Unable to distinguish greens from reds
• Achromatic Vision – Cannot distinguish any color; perceives only white, gray,
and black
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Cataract
• Pronounced– (KAT-ah-rakt)
• Defined– Lens in the eye becomes progressively cloudy
losing its normal transparency• Alters perception of images due to interference of
light transmission to retina
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Chalazion
• Pronounced– (kah-LAY-zee-on)
• Defined– Cyst or nodule on eyelid resulting from an
obstruction of a meibomian gland, which is responsible for lubricating margin of the eyelid
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Conjunctivitis, Acute
• Pronounced– (kon-junk-tih-VYE-tis acute)
• Defined– Inflammation of mucous membrane lining the
eyelids and covering the front part of the eyeball
– Also called “Pinkeye”
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Corneal Abrasion
• Pronounced– (COR-nee-al ah-BRAY-zhun)
• Defined– Disruption of the cornea’s surface epithelium
commonly caused by an eyelash, a small foreign body, contact lenses, or a scratch from a fingernail
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Diabetic Retinopathy
• Pronounced– (dye-ah-BET-ik reh-tin-OP-ah-thee)
• Defined– Condition that occurs as a consequence of an
8 to 10-year duration of diabetes mellitus in which the capillaries of retina experience scarring
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Diabetic Retinopathy
• Causes of retinal capillary scarring– Abnormal dilation and constriction of vessels– Hemorrhages– Microaneurysms– Abnormal formation of new vessels causing
leakage of blood into the vitreous humor• Leakage causes permanent decline in sharpness
of vision
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Ectropion
• Pronounced– (ek-TROH-pee-on)
• Defined– “Turning out” or eversion of the eyelash
margins from the eyeball leading to exposure of the eyelid and eyeball surface and lining
• Occurs especially in the lower eyelid
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Entropion
• Pronounced– (en-TROH-pee-on)
• Defined– “Turning in” of the eyelash margins resulting
in the sensation similar to that of a foreign body in the eye (redness, tearing, burning, and itching)
• Occurs especially in the lower margins
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Exophthalmia
• Pronounced– (eks-off-THAL-mee-ah)
• Defined– Abnormal protrusion of the eyeball(s) usually
with the sclera noticeable over the iris– Typically due to an expanded volume of
orbital contents
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Glaucoma
• Pronounced– (glau-KOH-mah)
• Defined– Ocular disorders identified as a group due to
the increase in intraocular pressure
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Glaucoma• Chronic open-angle glaucoma
– Primary disorder– Breakdown in drainage system of the
circulation of aqueous humor• Gradual elevation of internal pressure leads to
decreased blood supply to optic nerve and retina• Peripheral vision is gradually lost when untreated
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Glaucoma• Acute closed-angle glaucoma
– Mouth of drainage system is narrow and closes completely
– Allowing no flow of aqueous humor• Rapid occurrence characterized by severe pain,
blurred vision, photophobia, redness, and seeing “halos” around light
• If untreated, person can lose his or her sight within several days
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Hemianopia
• Pronounced– (hem-ee-an-NOP-ee-ah)
• Defined– Loss of vision or blindness in one-half of the
visual field
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Hordeolum (Stye)
• Pronounced– (hor-DEE-oh-lum)
• Defined– Bacterial infection of an eyelash follicle or
sebaceous gland– Originating with redness, swelling, and mild
tenderness in margin of eyelash
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• Pronounced– (high-per-OH-pee-ah)
• Defined– Refractive error in which the lens of the eye
cannot focus on an image accurately– Results in blurred vision due to light rays
focused behind the retina because eyeball is shorter than normal
• Also called farsightedness
Hyperopia
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Hyperopia
Hyperopia (Farsightedness)
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Hyphema (Hyphemia)
• Pronounced– (high-FEE-mah)
• Defined– Bleed into anterior chamber of eye – Resulting as a postoperative complication or
from a blunt eye injury
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• Pronounced– (kair-ah-TYE-tis)
• Defined– Corneal inflammation caused by a
microorganism, trauma to eye, a break in sensory innervation of cornea, hypersensitivity reaction, or a tearing defect
– May be due to dry eyes or ineffective eyelid closure
Keratitis
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Myopia
• Pronounced– (my-OH-pee-ah)
• Defined– Refractive error in which the lens of the eye
cannot focus on an image accurately– Resulting in blurred distant vision due to light
rays focused in front of retina because eyeball is longer than normal
• Also known as nearsightedness
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Myopia
Myopia (nearsightedness)
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• Pronounced– (nik-tah-LOH-pee-ah)
• Defined– Inadequate vision at night or in faint lighting
following reduction in synthesis of rhodopsin– Compound in rods of retina that enables the
eye to adjust to low-density light
Nyctalopia(Night Blindness)
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• Pronounced– (niss-TAG-mus)
• Defined– Vertical, horizontal, rotary, or mixed rhythmic
involuntary movements of the eye(s)• Caused by use of alcohol or certain drugs, lesions
on the brain or inner ear, congenital abnormalities, nerve injury at birth, or abnormal retinal development
Nystagmus
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• Pronounced– (off-THAL-mee-ah nee-oh-nay-TOR-um)
• Defined– Purulent (contains pus) inflammation of
conjunctiva and/or cornea in newborn• Cause of the keratitis and conjunctivitis results
from newborn’s exposure to viral, bacterial, chemical, or chlamydial agents
Ophthalmia Neonatorum
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Presbyopia
• Pronounced– (prez-bee-OH-pee-ah)
• Defined– Refractive error occurring after age of 40– Lens of the eye(s) cannot focus on an image
accurately due to loss of elasticity • Also called farsightedness due to better clarity of
distant objects
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• Pronounced– (ter-IJ-ee-um)
• Defined– Irregular growth developing as a fold in the
conjunctiva– Usually on nasal side of the cornea– Disrupts vision if it extends over pupil
• Can be caused by allergies and excessive ultraviolet light exposure
Pterygium
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Pterygium
Pterygium
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Retinal Detachment• Pronounced
– (RET-in-al detachment)
• Defined– Partial or complete splitting away of the retina
from the pigmented vascular layer called the choroid, interrupting vascular supply to the retina and thus creating a medical emergency
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Retinal Tear
• Pronounced– (RET-in-al tear)
• Defined– Opening in retina that allows leakage of
vitreous humor
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• Pronounced– (skleh-RYE-tis)
• Defined– Presence of inflammation in the white,
outside covering of the eyeball, the sclera• Symptoms include intense redness with dull pain
and possibly some loss of vision
Scleritis
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Scotoma
• Pronounced– (skoh-TOH-mah)
• Defined– Defined area in one or both eyes– Decreased visual function
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Strabismus
• Pronounced– (strah-BIZ-mus)
• Defined– Failure of eyes to gaze in same direction due
to weakness in muscles controlling position of eye
• Most common type is nonparalytic strabismus• Inherited defect in which the eye position of the
two eyes has no relationship
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Strabismus
• Convergent Strabismus– Also known as “Crosseye” – Also known as “Esotropia”– Affected eye turns inward
• Usually develops in infancy or early childhood
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Strabismus
• Divergent Strabismus– Also known as “Walleye”– Also known as “Exotropia”– Affected eye turns outward
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Strabismus
Strabismus(A) Convergent(B) Divergent
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• Pronounced– (sin-EK-ee-ah)
• Defined– Adhesion in eye that develops as a
complication of trauma or surgery– Secondary condition of one of the following
pathological conditions: cataracts, glaucoma, keratitis, or uveitis
• Adhesion causes the iris to adhere to lens or cornea
Synechia
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Trachoma
• Pronounced– (tray-KOH-mah)
• Defined– Infectious eye disease caused by Chlamydia
trachomatis– Chronic and will lead to blindness without
treatment• Early symptoms include tearing, pain,
photophobia, and inflammation
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• Pronounced– (yoo-vee-EYE-tis)
• Defined– Inflammation of all or part of middle vascular
layer of eye made up of the iris, ciliary body, and choroid
• Characterized by blurred vision, pain, redness, pupillary constriction, and intense photophobia
Uveitis
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DIAGNOSTIC TECHNIQUES, TREATMENTS
AND PROCEDURES
The Eye
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• Corneal transplant– Surgical transplantation of a donor cornea
(cadaver’s) into the eye of a recipient usually under local anesthesia
• Electronystagmography– Group of tests used in evaluating vestibule-
ocular reflex• Normal reflex produced by stimulation of
vestibular apparatus in which eye position compensates for motion of the head
Diagnostic Techniques, Treatments, and Procedures
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• Electroretinogram (ERG)– Recording of changes in electrical potential of
retina after stimulation of light
• Extracapsular Cataract Extraction (ECCE)– Surgical removal of anterior segment of lens
capsule along with lens allowing for insertion of an intraocular lens implant
Diagnostic Techniques, Treatments, and Procedures
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• Fluorescein staining– Application of a fluorescein-stained sterile
filter paper strip moistened with a few drops of sterile saline or sterile anesthetic solution to the lower cul-de-sac of the eye to visualize a corneal abrasion
Diagnostic Techniques, Treatments, and Procedures
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• Gonioscopy– Process of viewing anterior chamber angle of
eye for evaluation, management, and classification of normal and abnormal angle structures
– Intraocular lens implant• Surgical process of cataract extraction and
insertion of an artificial lens in patient’s eye– Restores visual acuity and provides improved depth
perception, light refraction, and binocular vision
Diagnostic Techniques, Treatments, and Procedures
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• Iridectomy– Extraction of a small segment of the iris to
open an anterior chamber angle and permit the flow of aqueous humor between the anterior and posterior chambers
– Relieves person’s intraocular pressure
Diagnostic Techniques, Treatments, and Procedures
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• Keratoplasty– Transplantation of corneal tissue from one
human eye to another to improve vision in affected eye
• Also called corneal grafting
Diagnostic Techniques, Treatments, and Procedures
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• Laser in situ Keratomileusis (LASIK)– LASIK procedure is a form of laser vision
correction for nearsightedness (myopia)
• Ophthalmoscopy– Examination of external and internal structures
of the eye– Utilizes an ophthalmoscope
Diagnostic Techniques, Treatments, and Procedures
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Diagnostic Techniques, Treatments, and Procedures
• Pachymetry– Measures thickness of cornea
• Patient’s eyes are numbed • Uses an ultrasonic-wave instrument to gauge
thickness of each cornea
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• Phacoemulsification– Removing a lens by using ultrasound
vibrations to split up lens material into tiny particles that can be suctioned out of the eye
• Photo Refractive Keratectomy– Surgical procedure in which a few layers of
corneal surface cells are shaved off by an “excimer laser beam” to flatten cornea and reduce myopia or nearsightedness
Diagnostic Techniques, Treatments, and Procedures
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• Retinal Photocoagulation– Surgical procedure using an argon laser to
treat conditions such as retinal detachment, and diabetic retinopathy
• Retinal Detachment – argon laser used to create an area of inflammation, which will develop adhesions, causing a welding of the layers
• Diabetic Retinopathy – argon laser used to seal microaneurysms and areas of leakage, and to reduce risk of hemorrhage
Diagnostic Techniques, Treatments, and Procedures
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Diagnostic Techniques, Treatments, and Procedures
• Slit-Lamp exam– Examination of external and internal
structures of the eye using a low power microscope combined with a high-intensity light source focused to shine as a slit beam
• Also known as biomicroscopy
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• Tonometry– Process of determining intraocular pressure
by calculating resistance of eyeball to an applied force causing indentation
• Trabeculectomy– Surgical excision of a portion of corneoscleral
tissue to decrease intraocular pressure in persons with severe glaucoma
Diagnostic Techniques,Treatments, and Procedures
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• Trabeculoplasty– Surgical creation of a permanent fistula used to
drain fluid (aqueous humor) from the eye’s anterior chamber
– Usually performed under general anesthesia• Laser trabeculoplasty is an outpatient plastic
surgery approach used in management of glaucoma
Diagnostic Techniques, Treatments, and Procedures
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Overview of the Ear
• Two important functions of the ear– Enables us to hear– Sensory organ of balance or equilibrium
• Location of one ear on each side of head produces binaural hearing– Hearing from both sides
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• External ear– Visible portion not contained within the head– Auricle or pinna
• Cartilaginous flap or ear lobe
– External auditory canal• Tube leading from auricle to the middle ear• Lined with tiny hairs called cilia to aid in transmitting
sound waves inward
– Tympanic membrane (eardrum)• Separates external ear from middle ear
Structures of the Ear
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• Middle ear– Three tiny bones known as auditory ossicles– Malleus
• Resembles shape of a hammer• Connected to tympanic membrane and transmits
sound vibrations to second auditory ossicle
– Incus• Resembles shape of an anvil• Transmits sound vibrations from malleus to third
auditory ossicle
Structures of the Ear
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• Middle ear – Stapes
• Shaped like a tiny stirrup• Transmits sound vibrations from incus to inner ear
– Eustachian tube• Connects middle ear to pharynx• Auditory tube
– Oval window• Separates middle ear from inner ear• Base of stapes fits into oval window
Structures of the Ear
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• Inner ear– Vestibule
• Central portion of inner ear• Located next to stapes and between cochlea and
semicircular canals• Contains utricle and saccule-membranous
pouches or sacs that aid in maintaining balance
– Cochlea• Snail-shaped bony structure• Contains endolymph and perilymph• Auditory fluids that aid in transmission of sound
vibrations
Structures of the Ear
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• Inner ear – Organ of Corti
• True organ of hearing• Contained within the cochlea• Here, sound vibrations are converted into nerve
impulses that are transmitted to the brain for interpretation as hearing
– Semicircular canals• Located behind the vestibule• Three bony, fluid-filled loops that help to maintain
one’s balance
Structures of the Ear
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Structures of the Ear
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The Process of Hearing
Pathway of soundvibrations
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PATHOLOGICAL CONDITIONS
The Ear
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Cholesteatoma
• Pronounced– (koh-lee-stee-ah-TOH-mah)
• Defined– Slow-growing cystic mass made up of
epithelial cell debris and cholesterol found in the middle ear
• Occurs as a congenital defect or as a result of chronic otitis media
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Deafness, Conductive
• Pronounced– (Deafness kon-DUK-tiv)
• Defined– Hearing loss caused by breakdown of the
transmission of sound waves through the middle and/or external ear
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Deafness, Sensorineural
• Pronounced– (Deafness sen-soh-ree-NOO-ral)
• Defined– Hearing loss caused by inability of nerve
stimuli delivered to brain from inner ear due to damage in auditory nerve or cochlea
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Impacted Cerumen
• Pronounced– (Impacted seh-ROO-men)
• Defined– Excessive accumulation of waxlike secretions
from glands of external ear canal
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Labyrinthitis
• Pronounced– (lab-ih-rin-THIGH-tis)
• Defined– Infection or inflammation of the labyrinth or
the inner ear– Specifically, the three semicircular canals in
the inner ear– Fluid-filled chambers and control balance
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Mastoiditis
• Pronounced– (mass-toyd-EYE-tis)
• Defined– Inflammation of mastoid process– Usually an acute expansion of an infection in
the middle ear – Otitis media
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Ménière's Disease
• Pronounced– (may-nee-ARYZ dih-ZEEZ)
• Defined– Chronic inner ear disease– Over accumulation of fluid in the labyrinth– Characterized by recurring episodes of
vertigo, hearing loss, feeling of pressure or fullness in the affected ear, and tinnitus
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Otitis Externa (O.E.) (Swimmer’s Ear)
• Pronounced– (oh-TYE-tis eks-TER-nah)
• Defined– Inflammation of outer or external ear canal
• Result of growth of bacteria or fungi in external ear• Major symptom is pain, especially when the ear is
tugged on, along with a red swollen ear canal
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Otitis Media, Acute (A.O.M.)
• Pronounced– (oh-TYE-tis MEE-dee-ah)
• Defined– Middle ear infection– Predominately affects infants, toddlers, and
preschoolers
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Serous Otitis Media (S.O.M.)
• Pronounced– (SEER-us oh-TYE-tis MEE-dee-ah)
• Defined– Collection of clear fluid in middle ear that may
follow acute otitis media or be due to an obstruction of eustachian tube
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• Pronounced– (SOO-per-ah-tiv oh-TYE-tis MEE-dee-ah)
• Defined– Purulent collection of fluid in the middle ear– Person may experience pain (possibly
severe), an elevation in temperature, dizziness, decreased hearing, vertigo, and tinnitus
– Also called acute otitis media
Suppurative Otitis Media
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Otosclerosis
• Pronounced– (oh-toh-sklair-OH-sis)
• Defined– Condition in which footplate of stapes
becomes immobile and secured to oval window
– Results in a hearing loss
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Perforation of Tympanic Membrane
• Pronounced– (per-for-AY-shun of the tim-PAN-ik
membrane)
• Defined– Rupture of tympanic membrane or eardrum
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DIAGNOSTIC TECHNIQUES, TREATMENTS,
AND PROCEDURES
The Ear
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Diagnostic Techniques, Treatments, and Procedures
• Audiometry – Process of measuring how well an
individual hears various frequencies of sound waves
• Otoscopy– Use of an otoscope to view and examine
tympanic membrane and various parts of outer ear
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• Tuning Fork Test (Rinne Test)– Examination that compares bone
conduction and air conduction
• Tuning Fork Test (Weber Test)– Examination used to evaluate auditory
acuity as well as discover whether a hearing deficit is a conductive loss or a sensorineural loss
Diagnostic Techniques, Treatments, and Procedures
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• Otoplasty– Removal of a portion of ear cartilage to bring
pinna and auricle near head
• Stapedectomy– Microsurgical removal of stapes diseased by
otosclerosis– Typically under local anesthesia
Diagnostic Techniques, Treatments, and Procedures
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• Hearing aids– Devices that amplify sound to provide
precise perception and interpretation of words • In-canal style – fits completely into ear canal• In-ear style – worn in external ear• Behind-ear style – placed behind ear• Body hearing aid – sound delivered to ear canal
by way of microphone
Diagnostic Techniques, Treatments, and Procedures
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• Myringotomy– Surgical procedure with insertion of a small
ventilation tube into inferior segment of tympanic membrane
• Tympanotomy– Also called a myringotomy
Diagnostic Techniques, Treatments, and Procedures
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• Myringoplasty– Surgical repair of the tympanic membrane
with a tissue graft after a spontaneous rupture that results in hearing loss
• Tympanoplasty– Also called a myringoplasty
Diagnostic Techniques, Treatments, and Procedures