sensorineal disorders students

8/3/2019 Sensorineal Disorders Students

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1. ANATOMY AND PHYSIOLOGY OF THE EYES

** ACCESSORY ORGANS

Eyelids /palpebrae

-upper/lower

Thin elastic skin that covers striated and smooth

muscles.

- Shades the eyes during sleep, Protect the

anterior portion of the eyes , protect fromexcessive light and foreign objects, spread

lubricating secretions over the eyeballs.

Contains the sebaceous, sweat and lacrimal

glands, puncta and eyelashes.


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2. Eyebrows

3. Lacrimal apparatus Lacrima-Tears

Group of structures that produces and drains

tears.

**Lacrimal glands-produces 1 ml of tears a day- cleans, lubricates and moistens the eyeball

Composed of lipoid, aqueous and mucoids,

**lysozome = bactericidal enzyme

Secreted in response to reflex or emotional

stimuli

Tears evap passing to lacrimal canals then

nasal cavity


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LAYERS OF THE EYE

A. FIBROUS OUTER LAYER

1. Conjunctiva

Thin, transparent, mucous membrane containing

fine blood vessels.

Provides a barrier to external environment and

nourishment to the eye.

Bulbar conjunctiva Covers the sclera

Palpebral conjunctiva Lines the inner surface the upper & lower eyelids


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2. Sclera

White of the eyes

A dense, fibrous structure

Helps maintains the shape of the eyeball andprotects the intraocular contents from trauma.

Makes up posterior 5/6 of the eye


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3. Cornea

Main refracting surface of the eye

Transparent, avascular, dome-like structure

Constitute the modified anterior 1/6 of the outerlayer

Composed of 5 layers: epithelium, Bowmans

membrane, stroma, Descemets membrane and

endothelium.

Forms the most anterior portion of the eyeball

** no blood or lymphatic vessels which makes cornealtransplants individual to another successful, rejection

rarely occurs-avascular, antibodies causing rejection do

not circulate


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B. VASCULAR MIDDLE LAYER

1. Iris

- colored part of the eye, highly vascularized,

pigmented collection of fibers surroundingthe pupil

*pupil iriss central opening, permits light to

enter the eyes, dilates and constricts in

response to light

normal: round and constricts symmetrically

when a bright light is shown. Diameter: 3-5 mm depending on age


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2. Ciliary body

Manufactures aqueous fluid (supplies nutrients

and removes waste)

Controls accommodation through the zonularfibers and ciliary muscles

3. Choroid

Lies between the retina and sclera

Supplies blood to the portion of the retinaclosest to it.

Absorbs light


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C. INNER LAYER

Retina

Egg-shaped, multilayered, light sensitive

membrane containing network of specialized

cells

It receives visual stimuli and transmits images to

brain for processing Connected to brain by a circuit of millions

neurons in the optic nerve.

**Landmarks of retina

1.Optic disc/blind spot(not sensitive to light) Entrance of the optic nerve to the retina

Pink, oval or circular and has sharp margins

Point where there are no photoreceptors in the retina


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2.Macula, responsible for central vision

Fovea, most sensitive area

3. Retinal vessels

Two important layers: Retinal Pigment Epithelium (RPE)

y Absorption of light

y Outer layer

Sensory Retina

y Contains photoreceptor cells

y Inner layer

Rods

Cones


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Rods mainly for night vision , black and white,

low /dim light.

- high density in the peripheral portion of the

visual fieldCones color vision, high visual acuity in bright

light(sharpness of vision)fine detail. Moonlight-

cant see colors coz only rods are functioning-

most concentrated in fovea

*Fovea - area of sharpest vision coz of high density

of cones

**each eye has about 125 million rods and 7 million cones


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STRUCTURES INSIDE THE EYES

Lens

Lies behind the pupil and iris

Colorless, almost transparent, biconvex structureheld in position by zonular fibers.

Enables accommodation (ability to focus or

refocus)

Aqueous fluid Supplies nutrients and remove waste

Anterior to the lens


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Vitreous body

Soft, colorless, transparent, jelly-like

substance composed of 99% H2O, some salts

and mucoprotein. Keeps eye shape

Posterior to the lens


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Extraocular Muscles

4 rectus muscles(superior rectus, lateral

rectus, inferior rectus,

medial rectus muscle-responsible foropposing the movement of the lateral

rectus muscle))

2 oblique muscles(superior oblique,

inferior oblique)

Innervated /stimulated by cranial nerves

(CN III, IV, VI)


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ACCOMODATION OF THE EYES TO LIGHT

**Accommodation-ability to adjust focusing

apparatus to account for changes in distance

from the viewed object- lens changes shape to accommodate near

vision

- pupil changes diameter to help

accommodation

Constriction of pupils- narrowing the

diameter of the hole through which light

enters


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Convergence- medial movement of two

eyeballs so they are both directed toward

the object being viewed.

The nearer the object, the greater the

degree of convergence needed to maintain

single binocular vision=both eyes focus ononly one set of objects.


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REFRACTION

Light waves travel parallel to each other, but

they bend when they pass from one medium

to a medium with a different density;bending refraction

Light waves that enter the eye from the

external air are refracted so that they

converge at the retina as a sharp, focusedpoint focal point


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Before light reaches the retina, it passes

through the 1) cornea, 2) aqueous humor of

the anterior chamber between iris and lens,

3) lens, 4) gelatinous vitreous humor in thevitreous chamber behind the lens.

Refraction takes place as light passes through

the surfaces of the retina(convex,

nonadjustable lens) and again as it passesthrough the anterior and posterior surfaces

of the lens(convex, adjustable lens)


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A Normal eye can bring objects more than 6

meters(20ft) away to a sharp focus on the

retina

*Emmetropia-vision is perfect whenparallellight rays are focused on the

retina


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*Myopia/Nearsightedness occurs when lightrays come to a focus before they reach

retina, thus distant objects become blurred

- focalpoint falls in front of retina

- causedby elongated eyeball or a thickened

lens

- Correctedbyuse of a concave lens thatdiverges entering light rays so that they

have to travel further from the eyeball and

are focused directly on the retina.


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*Hypermetropia/farsightedness

- occurs when light rays are focused beyond the

retina where near objects appear blurred.

- Caused by shortened eyeballora thinnedlens

- Corrected by use ofconvex lens thatconverges enteringlight raysso that theyfocus directly on the retina.


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Astigmatism

- occurs when the curvature of the cornea or

lens is not uniform, thus part of the imageformed on the retina is unfocused.

- An irregularity in the curve of the cornea

causing distortion of the visual image

(decreased acuity of both distance and nearvision)

- Can be corrected with lenses that have

greater bending power in one axis than in

others.(rigid or soft toric contact lenses-curved to have different length along each

axis)


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near point vision- minimum distance from eyethat an object can be clearly focused with

maximum effort.

PRYSBYOPIA-(prysbys-old)- the lens loseselasticity and ability to accommodate due toaging

Age 40, the near point of vision may increase to

20cm(8 in)and at age 60 to 80 cm (31in)

Prsybyopia begins at midforties-thus those who

wear glasses need bifocals and those who have

not yet wearing glasses now require reading

glasses


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Night blindness / nyctalopia

- inability to see well at low light levels

- caused by prolonged vitamin A deficiency

and the non consequent inability tosynthesize a normal amount of RHODOPSIN single type of photo pigment in rods.

rhodo-rose, opsis-vision


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Color blindness/ color vision deficiency

- can be result of brain or nerve damage but

is usually an inherited condition

**Red-green deficiency(common forms)- redor green sensitive cones are missing or

defective

* Deuteranopia- color blindness due to no

green sensitive cones* Protanopia- no red sensitive cones


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Ocular Examination1. Visual acuity

Snellen chart- eye chart use to measure

visual acuity

Named after Herman Snellen Dutchopthalmologist who developed the chart

during 1862

Others used eye chart by Ian Bailey and Jan

Lovie


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Record each eye

Reading

Finger count or hand motion

20/20 means the patient can read the

20 line at a distance of 20 feet

**optotypes - symbols/letters in the chart


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If patient cant read the largest letter

(20/200 line) move the patient or chart until

patient can identify the letter

- 20/200- legally blind If client can only recognize E on the top line

with a distance of 10 ft, visual acuity

=10/200

If patient cant see Letter at any distance,use count fingers (CF)

The examiner holds up a random number of

finger and asks the patient to count the

number he sees


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If the patient correctly identify the numbers

of fingers at 3 ft, the examiner record CF/3.

If patient is unable to count fingers, use

hand motion (HM).The examiner raises onehand up and down or moves it side to side

and ask patient which direction the hand is

moving

A patient who could only perceived light Light perception (LP)

The vision of client who is unable to perceive

light-No light perception(NLP)


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Categories of Visual Impairment

Category ofvisual impairment Visual Acuity(Best corrected)

Low vision

1 6/18

3/10(0.3)

20/70

2 6/60

1/10 (0.1)

20/200

Blindness

3 3/60(fingers counting at 3m)

1/20(0.5)

20/400

4 1/60(finger counting at 1 m

1/50(0.02)

5/300

5 No light perception


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2. Examination of the External Structures

Note any evidence of irritation, inflammatory

process, discharge, etc.

Assess eyelids and sclera-Ptosis: drooping eyelid

- lid retraction: too much of the eye is exposed

Lid margins and lashes: no erythema, edema,

lesions

Normal Sclera: opaque and white


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Assess pupils and pupillary response in a

darkened room(pupillary reactions should be

checked with penlight-pupils are equally

reactive and regular)Normal pupil: black

Irregular pupil: may result from trauma,

previous surgery or disease process


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Note gaze(steady look), position of eyes, tilt

head-cranial nerve palsy

- Patient is asked to stare a target; each eye

is covered and uncovered quickly, noting anyshift in gaze.

Assess extra ocular movements(let patient

follow the examiners finger or hand light

through the 6 cardinal directions of gaze: upn down, right and left, diagonally)very

important when screening patients for ocular

trauma or neurologic disorders..


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Nystagmus: involuntary movement of eyes ,frequently composed of a mixture of slow

and fast movements of the eyes- can occur normally(tracking a visual

pattern)

- abnormal (situations where one would want

the eyes to be still, but they are in motion*Vertigo is often accompanied by nystagmus

Evoked nystagmus: caused by maneuver

e.g looking to one side- gaze evoked

nystagmus;head-shaking nystagmus- turning the

head back


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DIAGNOSTIC EVALUATION

1. Ophthalmoscopy

A. Direct opthalmoscope is a hand held

instrument with varying plus and minus lenses,lens can be rotated into place

examiner holds ophthalmoscope in the right hand and

uses the R eye to examine the patients Right eye,

then switches to left hand and examine the left eye

Examines the cornea, lens, and retina


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B. Indirect Opthalmoscope

- commonly used by ophthalmologist.

- It produces bright and intense light.

- used in conjunction with a hand held 20 diopterlens.

- enables the examiner to see larger areas of the

retina, in an unmagnified state.


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Abnormal findings:

Arteriosclerosis silvery or coppery appearance(veins)

Intraretinal hemorrhages red smudges or flame-

shaped with Hpn

Presence of lipid patients with hypercholesterolemiaor diabetes

Microaneurysms little red dots, nevi

Drusen small, hyaline, yellowish spots beneath the

retina (commonly found in macular degeneration)


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2. Slit-lamp examination

Binocular microscope mounted on a table.

Magnification is 10-40 times

Uses width, intensity & angle of the light


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3. Color vision testing

Use of Ishihara polychromatic plates

Primary colors are integrated into a background

of secondary colors arranged in numbers orgeometric shapes


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4. Amsler grid

Use for patients with macular problems(macular

degeneration)

Consists of a geometric grid of identical squareswith a central fixation point.

Detects neovascular choroidal membrane

development (advanced stage of macular

degeneration characterized by the growth of

abnormal choroidal vessel).


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6. Angiography

Fluorescein

Evaluates macular edema by recording the appearance

of blood vessels inside the eyes through a rapid

sequence photograph of the fundus (posterior innerpart of eye)

Documents macular capillary nonperfusion

Identifies retinal and choroidal neovascularization-

growth of abnormal new blood vessels

Indocyanine green

Evaluates abnormalities in the choroidal vasculature


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7. Tonometry

Measures intraocular pressure (IOP)

Uses applanation tonometer and Tono-Pen

Pressure is measured in millimeters ofmercury(mm Hg)

High reading: high pressure; low reading: low

pressure


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8. Gonioscopy

Visualizes the angle of the anterior chamber to

identify abnormalities in appearance and

measurements.

Uses a refracting lens direct or indirect

a. indirect - lens views the mirror image of the

opposite anterior chamber angle and can only be

used with a slit lamp

b. direct- lens gives a direct view of the angleand its structures.


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9. Perimetry testing

Evaluates field of vision or the area or extent of

physical space visible to an eye in a given

position

Average extent: 65 degrees upward, 75 degrees

downward, 60 degrees inward and 95 degrees

outward when eye is in primary gaze(looking

forward)

Manual/automated perimetry Scotomas (deminished eyesight): blind areas in

the visual field


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10. Color Fundus Photography

used to detect and document retinal lesions.


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Ophthalmology study of the structures,

functions and diseases of the eye

Ophthalmologist a physician who specializesin the diagnosis and treatment of eye

disorders with drugs, surgery and corrective

lenses

Optometrist specialist with a doctorate inoptometry who is licensed to examine and

test the eyes and treat visual defects by

prescribing lenses.

Optician technician who fits, adjusts anddispenses corrective lenses prescribed by

ophthalmologist and optometrist


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B. ANATOMY AND PHYSIOLOGYOF EARS


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A. EXTERNAL EAR

AURICLE

PINNA- flap of elastic cartilage shaped like the

flared end of a trumpet and covered by skin.*helix rim of the auricle (posterior)

*lobule inferior part

Collects sound waves and directs

vibrations into the external auditory

canal.


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2. EXTERNAL AUDITORY CANAL

ACOUSTIC MEATUS - Curved tube(2.5 cm) that

lies in the temporal bone and leads from the

auricle to the eardrum.

Contains hair, sebaceous glands and

ceruminous glands.


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B. MIDDLE EAR

1. TYMPANIC MEMBRANE

EAR DRUM

- About 1 cm in diameter , pearly gray andtranslucent.

- Separates the external from the middle ear.

- Protects the middle ear.

- Conducts sound vibrations from the external tothe ossicles.

- Sound pressure is magnified 22 times.


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2. AUDITORY OSSICLES

- smallest bones

- assist in the transmission of sounds

Form a series of movable joints that

transmit sound to the inner ear. MALLEUS hammer

INCUS anvil

STAPES stirrup


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C. INNER EAR

1. BONY LABYRINTH

- Filled with fluid called perilymph.

- Encloses and protects the membranouslabyrinth.

COCHLEA resembles a snails shell about 3.5

cm long.

VESTIBULE contains the oval and roundwindows.

SEMICIRCULAR CANALS three tubes continuous

with the vestibule.


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2. MEMBRANOUS LABYRINTH

- Contains a fluid called endolymph and all thesensory receptors for hearing and equilibrium.

UTRICLE & SACCULE involved with linearmovements.

SEMICIRCULAR CANALS contains sensory

receptor organs which detect rotational

movement.

ORGAN OF CORTI/spiral organ end organ of

hearing. Transforms mechanical energy into

neural activity and separate sounds into

different frequencies.


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ASSESSMENT

1. Inspection of the external ear(lesions,

deformities, discharges, size for symmetry, angle

of attachment to the head).

Palpation on the mastoid-tenderness-acute

mastoiditis or (inflammation of the posteriorauricular node) sebaceous cyst and tophi on

pinna, seborrheic dermatitis


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2. Otoscopic examination-use to examine the

external auditory canal and tympanic

membrane with an otoscope.

*healthy tympanic pearly gray, positionedobliquely at the base of the canal


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3. Gross auditory acuity

a. Whisper test - cover the un tested earthen whisper from 1-2 feet out of the

patients sight.- normal acuity can repeat what was

whispered.


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b. Weber test -useful for detecting unilateral hearingloss.

- uses bone conduction to test lateralization of a

sound ( a tunning fork set in motion by grasping it

firmly by its stem and tapping it on the examiners

knee or hand. Patient is asked to identify if sound is

heard on the middle of the head, right ear/ left ear.)**normal hearing-hear sound equally, describe sound as

centered in the middle of the head

**conductive hearing loss sound is heard better in the

affected ear.**sensorineural hearing loss- sound lateralizes better to

the hearing ear.


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Conductive hearing loss (CHL)- occurs due to

mechanical problem in the outer or middle

ear. The ossicles (tiny bones) may not

conduct sound properly, or the eardrum may

not vibrate in response to sound; fluid in the

middle ear

Sensorineural hearing loss(SHL)- due to

problem with inner ear. It most often occurs

when tiny hair cells(nerve endings) that

move sound through the ear are injured,

diseased, do not work correctly, or have

died.


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c. Rinne test - examiner shifts the stem of avibrating tunning fork between to 2 positions 2

inches from the opening ear canal(air

conduction) and against the mastoid(bone

conduction). As the position changes, theclient is asked to indicate which tone is louder

or when the tone is no longer audible

**Normal-sound heard by air conduction is audible longer than

sound heard by bone conduction*useful for distinguishing between conductive hearing loss and

sensorineural hearing losses


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Hearing occurs when sound waves stimulates

the nerves of the inner ear. The sounds

travels along the nerve pathways

Sound waves can travel to the inner earthrough the ear canal, eardrum, and bones

of the middle ear (air conduction) or through

the bones around and behind the ear(bone

conduction)


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DIGNOSTIC EVALUATION

1. Audiometry Single most importantdiagnostic instrument in detecting hearing loss.

2 kinds:a)pure tone- sound stimulus consist of a pure

or musical tone (the louder the tone before

the patients perceives it, the greater the

hearing loss)b) speech audiometry spoken word is used to

determine the ability to hear and

discriminate sounds and words.


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Important Characteristics when determining


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Important Characteristics when determining

hearing

1. Frequency/tone number /speed of soundwaves vibrations

- measured in cycles per second(cps) or

hertz (Hz)

*low bass tones =50-60Hz

*shrill high pitched tones-10,000Hz or higher

****normal ear perceives sounds ranging in

frequency from20

-20

,000

Hz*** animals can hear up to 50,000 Hz

**Human speech 500-3,000 Hz.


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2. Pitch describe frequency

*tone with 100 Hz is low pitch*tone of 10,000 Hz high pitch

3. Intensity-loudness

- unit for measuring loudness is

Decibel(dB); the pressure exerted bysounds

*Hearing loss is measured in dB.


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shuffling paper in quite envt 15 dB

whisper 20dB

low conversation-40dBloud music (some concert)- 80-120,

jet plane 100 ft away-150dB

*Sounds louder than 80dB harsh and

damaging to the inner ear


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Loss in Decibels Interpretation

0- 15 Normal hearing

>15-25 Slight hearing loss

>25-40 Mild hearing loss

>40-55 Moderate hearing loss

>55-70 Moderate to severe hearing

loss

>70-90 Severe hearing loss

>90 Profound hearing loss


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Tympanogram impedance(prevention ofprogress) audiometry

- measures the middle ear muscle reflex to

sound stimulation and compliance of the

tympanic membrane by changing the earpressure in a sealed ear canal


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Auditory Brain Stem Response

- is a detectable electrical potential from

cranial nerve VIII and the ascending auditory

pathways of the brain in response to sound

stimulation. Electrodes are placed on thepatients head. Acoustic stimuli (Clicks are made

in the ear. )The resulting electro physiologic

measurements determine at which decibel level

a patient hears and whether there are anyimpairment along the nerve pathways.


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ElectronystagmographyENG test- it determines whether or not dizziness may be

due to inner ear disease.

4 parts

1. calibration test evaluates rapid eye movements

2. tracking test evaluates movements of eyes as

they follow a visual target

3. positional test- measures dizziness associated

with positions of the head

4. caloric test measures response to warm and

cold water circulated through a small, soft tube ear

canal.


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ENG is the gold standard for diagnosis of ear

disorders affecting one ear at a time, also useful

for diagnosis of BPPV(Benign Paroxysmal

Positional Vertigo) and bilateral vestibular loss.

Also used to assess the oculomotor andvestibular system and their corresponding

interaction. It helps in diagnosing Menieres Dse

and tumors of the auditory canal or posterior

fossa.

y Vestibular suppressants like sedatives,

tranquilizers, antihistamines, alcohol are

withheld for 24 hrs before testing


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Platform posturography

used to investigate postural controlcapabilities such as vertigo

- Patient stand on platform surrounded byscreens and different condition such as

moving platform or a stationary platform

with a moving screen. The responses of the

patient from the 6 diff. conditions are

measured and indicate which of the systems

are impaired.


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Sinusoidal Harmonic Acceleration/Rotary

Chair- use to assess vestibulo-ocular system

by analyzing compensatory eye movement in

response to the clockwise and counter

clockwise rotation of the chair

- determine whether or not dizziness ma

be due to a disorder of the inner ear or

brain


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3 parts of Rotational Chair testing

1. Chair test measures dizziness while being

turned slowly in a motorized chair-nystagmus

** persons with inner ear diseases becomes lessdizzy than do normal persons

2. Optokinetic test measures dizziness caused

by viewing of moving stripes

3. Fixation test measures nystagmus while theperson is being rotated, while they are

looking at a dot of light that is rotating withthem (Fixation suppression is impaired by CNS conditions and improved by bilateral vestibularloss.)


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Middle Ear Endoscopy

- performed as an office procedure to

evaluate suspected perilymphatic fistula and

new onset conducting hearing loss, anatomy

of the round window before transtympanic

treatment of Menieres disease, and the

tympanic cavity before ear surgery to treat

chronic middle ear and mastoid formations.


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THANK YOU!