clinical pract, chapter 6 eyes and ears

Visual acuity test

Visual acuity test

• screening test to detect deficiencies in vision

Color vision assessment

• Requires specially prepared colored plates

• Color blindness: inability to distinguish certain colors

• Red and green are most common

Hearing tests

• use of tuning fork or audiometer

• Audiometer

• MA should be alert to signs that indicate the patient might be having difficulty hearing

• Audiometer:

• instrument that emits sound waves at various frequencies

• Irrigation:

• washing a body canal with a flowing solution

• Instillation:

• dropping a liquid into a body cavity

Layers of the Eye

• Sclera:

• Choroid:

• Lens:

• Retina:

• Sclera:

• outer layer

• Composed of tough, white, fibrous connective tissue

• Front of sclera is modified to form cornea

• Cornea

• : transparent covering over the colored part of the eye (iris)

• Choroid

• middle layer

  • Composed of many blood vessels and is highly pigmented

  • Blood vessels:

  • Pigment:

  • Front part of choroid has specialized structures

• Blood vessels

• nourish the eye

• Pigment

• absorbs stray light rays

• Lens:

• focuses light rays on the retina

• Retina

• inner layer

  • Light rays come to a focus on it

  • Transmitted to brain by optic nerve to be interpreted

Front part of choroid has specialized structures

• Ciliary body

• Suspensory ligaments:

• Iris:

• *Pupil

• Ciliary body

• : muscles that control the shape of the lens

• Suspensory ligaments

• suspend the lens in place

• Iris:

• colored part of the eye that controls the size of the pupil

• *Pupil:

• : opening in the eye that permits entrance of light rays

Chambers of the Eye

• Anterior chamber:

• Posterior chamber:

• Anterior chamber:

• Area between the cornea and iris

• glaucoma

• Posterior chamber:

• Area between the iris and lens

Substance of the eye

• Aqueous humor:

• Vitreous humor:

• Aqueous humor:

• Fills anterior and posterior chambers

• Vitreous humor:

• Transparent jelly-like material

• Fills eyeball between the lens and retina

• Function: maintains shape of the eyeball

Conjunctiva

• Membrane that lines eyelids and covers front of the eye except for the cornea

• Conjunctiva covering the sclera: transparent

• Conjunctivitis:

• inflammation of the conjunctiva

cones

detect blue, green and red

rods

detect black and white

special cells

cones and rods connect to neurons and form the optic nerve

• glaucoma

increase IO pressure due to failure to properly drain the aqueous humor

Normal visual acuity:

• Can see clearly and able to distinguish fine details at a close and long distance

visual acuity:

• Acuteness or sharpness of vision

• Most common cause of defects in visual acuity

Errors of refraction

Refraction

bending of the parallel light rays coming into the eye so that they can be focused on the retina

Error of refraction:

light rays are not being bent properly

• Are not focused on retina adequately

• Caused by defect in the shape of the eyeball

• Can be improved with corrective lenses

Myopia

(nearsighted):

• eyeball is too long from front to back

• Causes light rays to be brought to a focus in front of retina

  • Difficulty seeing objects at a distance

  • May squint and have headache from eyestrain

  • Corrective lenses (eyeglasses, contact lenses) or laser eye surgery can correct the condition

    • Allows light rays to come to a focus on retina

Hyperopia

(farsighted):

• eyeball is too short from front to back

• Causes light rays to be brought to a focus behind the retina

  • Difficulty viewing objects at a reading or working distance

  • May have blurring, headache, and eyestrain while performing close-up tasks

  • Corrective lenses can correct the condition

    • Cause light rays to come to a focus on the retina

Astigmatism:

• Causes distorted and blurred vision for both near and far objects

Normal cornea

• Round or spherical shape

• Smooth

With astigmatism cornea

• is curved into an oval shape

• Causes light rays to focus on two different points on the retina (instead of one point)

• Often occurs with myopia or hyperopia

• Can be corrected with corrective lenses

Presbyopia:

• decrease in elasticity of the lens

• Usually begins after age 40 years

• Results in a decreased ability to focus clearly on close objects

• Can be corrected with corrective lenses (reading glasses)

Ophthalmologist:

• physician specializing in the diagnosis and treatment of diseases and disorders of the eye

• Prescribes ophthalmic and systemic medications

• Performs eye surgery

Optometrist:

• licensed primary healthcare provider who has expertise in measuring visual acuity and prescribing corrective lenses

• Can diagnose and treat disorders and diseases of the eye

• Prescribes ophthalmic medications

• Not a physician: cannot prescribe systemic medications or perform eye surgery

Optician:

professional who interprets and fills prescription for eyeglasses and contact lenses

Assessment of Distance Visual Acuity (DVA)

• Used to diagnose myopia

• Snellen eye chart most often used

Types of charts for DVA

• Letters

• Capital letter E

• Pictures of familiar objects

• Letters chart

• in decreasing sizes

  • Used with school-aged children and adults

• Capital letter E chart

• in decreasing sizes (arranged in different directions)

  • Used for preschool children, non-English-speaking people, nonreaders

• Pictures of familiar objects chart

• Used for preschool children

• Less accurate because some children may be unable to identify objects

Conducting a Snellen Test

• Perform the test in a well-lit room free from distractions

• Performed at a distance of 20 feet

• Two numbers next to each row of letters

  • Number above the line:

  • Number below the line:

• Acuity of each eye is measured separately R-->L

• Eye occluder:

• Instruct patient to leave eye not being tested open

  • Closing eye: causes squinting of eye being tested

• Number above the line:

• distance at which the test is conducted (20 feet)

• Number below the line:

• distance from which a person with normal visual acuity can read the row of letters

• Normal DVA

• 20/20

• Patient can read at 20 feet what a person with normal vision acuity can read at 20 feet

• DVA: 20/30

• Smallest line (30) the individual could read at 20 feet

• People with normal acuity: can read this line at 30 feet

• DVA: 20/15

• Smallest line (15) the individual could read at 20 feet

• Indicates above-average DVA

• People with normal acuity: can read at 15 feet

• If patient wears eyeglasses or contact lenses on a Snellen test (except reading glasses)

• Keep them on during the test

• Record in chart that corrective lenses were worn

• Eye occluder

• held over eye not being tested

  • Patient’s hand should not be used

    • May encourage peaking through fingers, especially in children

Assessing Distance Visual Acuity in Preschool Children

• Snellen Big E chart used

• Explain procedure completely to child

  • Tell child you will be playing a pointing game

  • Do not force child: results would be inaccurate

• Draw a capital E on an index card

  • Teach child to point in the direction of the open part of the E by turning the card in different directions

  • Phrases to describe open part of E: “fingers” or “legs of table”

  • Allow child to practice

  • Praise child when correct

• Parent may need to help child hold occluder in place

Assessment of Near Visual Acuity (NVA)

• Assesses patient’s ability to read objects close up

  • At a reading or working distance

• NVA card

• Patient is asked to read each line or paragraph

• Observe patient for unusual symptoms

  • Squinting, tilting of head, watering of eyes

    • Indicates patient is having difficulty reading card

• Patient continues until reaching smallest line that can be read

• Record results as smallest type patient could read with each eye

  • Recording based on type of test card used

(NVA)

• Used to detect hyperopia and presbyopia

• NVA card

• contains different sizes of type

  • Ranging from size of newspaper headline down to very small print

• NVA card: forms

• Printed paragraphs

• Printed words

• Pictures

• To perform NVA testing

• Perform test in a well-lit room free of distractions

• Patient holds card at a distance of 14 to 16 inches

• Reading glasses should be worn (if patient uses them)

• Each eye is tested separately

• Eye occluder held over the eye not being tested

  • Instruct patient to keep covered eye open

    • Closing causes squinting of eye being tested

Assessment of Color Vision

• Classification of defects in color vision

  • Congenital defect:

  • Acquired defect:

• Color vision tests

  • Detect congenital color vision defects

  • Often performed in medical office

• Basic color vision screening test

• Congenital defect

• most common

  • Inherited (present at birth)

  • Most often affects males

• Acquired defect:

• acquired after birth

  • Eye or brain injury

  • Disease

  • Certain drugs

• Basic color vision screening test

• Ask patient to identify red and green lines on the Snellen chart

Ishihara Test

• Detects

  • Total congenital color blindness

  • Red-green color blindness

  • Conduct test in a quiet room

  • Illuminated by natural daylight (if possible)

  • Using bright sunlight: can change shades of color on plates

• Test consists of 14 color plates

• Defect in color vision: patient referred to ophthalmologist or optometrist

• Ishihara book

• Series of plates consisting of colored dots

  • Forms a numeral against a background of dots of contrasting colors

• Patients with normal color vision: read appropriate numeral

• Patients with defects read dots as

  • Not forming a number at all

  • Forming a different number

• First plate

• can be read correctly by all patients

  • Used to explain test procedure to patient

• Plates with winding colored lines

• For patients unable to identify numbers by name

  • Preschool children

  • Non-English-speaking people

• Patient is asked to trace line formed by the colored dots

• Using a cotton swab or pencil eraser

• Do not allow patient to use finger

  • Over time: soiled fingers can degrade plates

• Test consists of 14 color plates

• Basic test: plates 1 through 11

• Further assessment of patients with red-green deficiency: plates 12 through 14

• Normal color vision:

• 10 or more plates read correctly

• Color vision deficiency:

• 7 or fewer plates read correctly

Eye Irrigation

• Washing the eye with a flowing solution

purpose of eye irrigation

• Cleanse the eye by washing away

  • Foreign particles

    • Ocular discharges

    • Harmful chemicals

• Relieve inflammation through application of heat

• Apply an antiseptic solution

Eye Instillation

• Dropping of a liquid into the lower conjunctival sac

• Medications instilled in eye may come in the form of

  • Liquid

  • Ointment

purpose of eye instillation is

• Treat eye infections (with medications)

• Soothe an irritated eye

• Dilate the pupil

• Anesthetize the eye during eye examination or treatment

• Liquid

• (ophthalmic drops)

  • Usually dispensed in a flexible plastic container with an attached dropper

• Ointment

• Dispensed in a small metal tube with tip for applying medication

red and green

most common color blindness

cornea color

transparent

sclera outer layer has

no pain receptors

choroid middle layer color

red

cataracts surgery

replaces lens

myopia point of focus

in front of retina

hyperopia point of focus

behind the retina

NVA is used to detect

both hyperopia and presbyopia

Functions of the Ear

• Hearing

• Equilibrium

Structure of the Ear

external

middle

inner

external ear

auricle

external auditory canal

tympanic membrane

auricle

pinna

• Flap of cartilage covered with skin

• Projects from side of head

• Receives and collects sound waves and directs them toward the external auditory canal

middle ear contains

ossicles

eustachian tube

inner ear

cochlea

semicircular canals

External auditory canal

• Extends from the auricle to the tympanic membrane

• External auditory meatus: opening of the canal

• Canal is 1 inch long in adults

• Lined with skin that contains fine hairs, nerve endings, glands

  • Glands secrete cerumen

• Canal has an S-shaped curve as it leads inward

• cerumen

• lubricates and protects the ear canal

• external auditory Canal must be straightened during

• Otoscopic examination

• Ear instillation

• Ear irrigation

• Aural temperature measurement

Tympanic membrane

• Located at the end of the canal

• Pearly gray semitransparent membrane

• Receives sound waves causing it to vibrate and produce a frequency of sound waves that are carried further into the middle ear