THE SPECIAL
SENSES
(EYE & EAR)
Overview of the Eye
• Eye acts much like a camera
– Lens of eye adjusts to bring object into
clear 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 the eye
• Image is transmitted to brain for interpretation
Structures of the Eye
(Front View)
• Sclera
– White portion of the eye
• Tough connective tissue
• Maintains the shape of the eyeball
• Serves as protective covering for the eye
• Iris
– Colored portion of the eye
• Pupil
– Opening in the center of the eye
– Controls the amount of light entering the
eye
Structures of the Eye
(Front View) (continued)
• 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) (continued)
Front View of the Eye
Structures of the Eye
(Front View) (continued)
• Eyelids
– Continuous with the skin and cover the eyeball
– Keep surface of eyeball lubricated and protected
from dust and debris through blinking motion
• Eyelashes
– Located along the edges of the eyelids
– Help protect eyeball by preventing foreign
materials and/or insects from coming in contact
with surface of eyeball
Structures of the Eye
(Cross Section)
• Sclera
– “White of the eye”
– Thinnest over the 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
the colored part of the eye
Structures of the Eye
(Cross Section) (continued)
• Conjunctiva
– Mucous membrane that lines inner surfaces
of the eyelids and outer surfaces of the eye
• Choroid
– Vascular middle layer of the eye
• Just beneath the sclera
• Contains extensive capillaries that provide
blood supply and nutrients to the eye
• Contains the iris, ciliary body, and suspensory
ligaments
Structures of the Eye
(Cross Section) (continued)
• Iris
– Colored portion of the eye
• Can be seen through the transparent corneal layer
• Pupil
– Located in center of iris
• Controls amount of light entering eye
• Lens
– Colorless biconvex structure that aids in
focusing the images clearly on the retina
Structures of the Eye
(Cross Section) (continued)
• Ciliary Body
– Located on each side of the lens
– Contains muscles that are responsible for
adjusting the lens to view near objects
• Suspensory Ligaments
– Radiate from the ciliary body and attach to
the lens
– Hold the lens in place
– Assist in adjusting the shape of the lens for
proper focusing of the eye
Structures of the Eye
(Cross Section) (continued)
• Retina
– Sensitive nerve cell layer
• Changes the energy of the light rays into nerve
impulses
• Transmits nerve impulses via optic nerve to
brain for interpretation of the image seen by
the 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) (continued)
• Retina (continued)
– Macula Lutea
• Oval, yellowish spot near the center of the
retina
– Fovea Centralis
• Small depression located within the macula
lutea
• Sharpest image is obtained when image
focuses directly on fovea centralis = central
vision
Structures of the Eye
(Cross Section) (continued)
• 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) (continued)
Lateral Cross
Section of the Eye
Structures of the Eye
(Cross Section) (continued)
• Anterior Cavity of the Eye
– Anterior Chamber
• Located in front of the lens
• Filled with clear, watery fluid called aqueous
humor
– Posterior Chamber
• Located behind the lens
• Also filled with aqueous humor – flows back
and forth between both chambers
Structures of the Eye
(Cross Section) (continued)
• Posterior Cavity of the Eye
– Posterior to the 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
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
Process of Vision (continued)
• 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
Diseases of the Eye
Astigmatism
• Pronounced
– (ah-STIG-mah-tizm)
• Defined
– A refractive error causing the light rays
entering the eye to be focused irregularly on
the retina due to an abnormally shaped
cornea
• Correction: contact lenses or eyeglasses, which
neutralize the defect
Blepharitis
• Pronounced
– (blef-ah-RYE-tis)
• Defined
– Inflammation of the eyelid margins stemming
from seborrheic, allergic, or bacterial origin
Blindness
• Pronounced
– (BLINDNESS)
• Defined
– The absence of vision or the need for assistive
devices and/or assistance from others to
accomplish daily activities due to the inability
to see
Monochromatism
(Color Blindness)
• Pronounced
– (mon-oh-KROH-mah-tizm)
• Defined
– An 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
Cataract
• Pronounced
– (KAT-ah-rakt)
• Defined
– Lens in the eye becomes progressively
cloudy losing its normal transparency
• Thus altering the perception of images due to
the interference of light transmission to the
retina
Conjunctivitis, Acute
• Pronounced
– (kon-junk-tih-VYE-tis acute)
• Defined
– Inflammation of the mucous membrane lining
the eyelids and covering the front part of the
eyeball
– Also called “Pinkeye”
Glaucoma
• Pronounced
– (glau-KOH-mah)
• Defined
– Ocular disorders identified as a group due to
the increase in intraocular pressure
Glaucoma (continued)
• 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
Glaucoma (continued)
• 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
Hyperopia
• Pronounced
– (high-per-OH-pee-ah)
• Defined
– A refractive error in which the lens of the
eye cannot focus on an image accurately,
resulting in impaired close vision that is
blurred due to the light rays being focused
behind the retina because the eyeball is
shorter than normal
• Also called farsightedness
Hyperopia (continued)
Hyperopia (Farsightedness)
Myopia
• Pronounced
– (my-OH-pee-ah)
• Defined
– A refractive error in which the lens of the
eye cannot focus on an image accurately,
resulting in impaired distant vision that is
blurred due to the light rays being focused
in front of the retina because they eyeball
is longer than normal
• Also known as nearsightedness
Myopia (continued)
Myopia (nearsightedness)
Presbyopia
• Pronounced
– (prez-bee-OH-pee-ah)
• Defined
– A refractive error occurring after the age of
40, when the lens of the eye(s) cannot
focus on an image accurately due to its
decreasing loss of elasticity resulting in a
firmer and more opaque lens
• Also called farsightedness due to better clarity
of distant objects
Strabismus
• Pronounced
– (strah-BIZ-mus)
• Defined
– Failure of the eyes to gaze in the same
direction due to weakness in the muscles
controlling the position of the eye
• Most common type is nonparalytic strasbismus,
an inherited defect in which the eye position of
the two eyes has no relationship
Strabismus (continued)
• Convergent Strabismus
– Also known as “Crosseye”
– Also known as “Esotropia”
– Affected eye turns inward
• Usually develops in infancy or early childhood
Strabismus (continued)
• Divergent Strabismus
– Also known as “Walleye”
– Also known as “Exotropia”
– Affected eye turns outward
Strabismus (continued)
Strabismus:
(A) Convergent;
(B) Divergent
Overview of the Ear
• Two important functions of the ear
– It enables us to hear
– It functions as the sensory organ of balance
or equilibrium
• Location of one ear on each side of head
produces binaural hearing
– Hearing from both sides
Structures of the Ear
• External Ear
– Visible portion of the ear not contained
within the head
– Auricle or pinna
• Cartilaginous flap that has a fleshy, lower
portion called the ear lobe
– External auditory canal
• Tube leading from the auricle to the middle ear
• Lined with tiny hairs called cilia which aid in
transmitting sound waves inward
– Tympanic membrane (eardrum)
• Separates external ear from middle ear
Structures of the Ear
(continued)
• Middle Ear
– Contains three tiny bones known as the
auditory ossicles
– Malleus
• Resembles the shape of a hammer
• Connected to tympanic membrane and
transmits sound vibrations to second auditory
ossicle
– Incus
• Resembles the shape of an anvil
• Transmits sound vibrations from malleus to
third auditory ossicle
Structures of the Ear
(continued)
• Middle Ear (continued)
– Stapes
• Shaped like a tiny stirrup
• Transmits sound vibrations from incus to the inner
ear
– Eustachian tube
• Connects the middle ear to the pharynx
• Also called the auditory tube
– Oval window
• Separates the middle ear from the inner ear
• Base of the stapes fits into the oval window
Structures of the Ear
(continued)
• Inner Ear
– Vestibule
• Central portion of the inner ear
• Located next to stapes and between cochlea
and semicircular canals
• Contains the 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
(continued)
• Inner Ear (continued)
– 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
(continued)
Structures of the Ear
The Process of Hearing
Pathway of Sound
Vibrations
Diseases of the Ear
Mėniėre’s Disease
• Pronounced
– (may-nee-ARYZ dih-ZEEZ)
• Defined
– Chronic inner ear disease in which there is
an 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
Otitis Externa
(Swimmer’s Ear)
• Pronounced
– (oh-TYE-tis eks-TER-nah)
• Defined
– Inflammation of the outer or external ear
canal
• Result of growth of bacteria or fungi in the
external ear
• Major symptom is pain, especially when the ear
is tugged on, along with a red swollen ear
canal
Otitis Media, Acute
• Pronounced
– (oh-TYE-tis MEE-dee-ah)
• Defined
– A middle ear infection, which predominately
affects infants, toddlers, and preschoolers
Suppurative Otitis Media
• Pronounced
– (SOO-per-ah-tiv oh-TYE-tis MEE-deeah)
• Defined
– A purulent collection of fluid in the middle
ear causing the person to experience pain
(possibly severe), an elevation in
temperature, dizziness, decreased hearing,
vertigo, and tinnitus
– Also called acute otitis media
OTOSCLEROSIS
• Pronounced
– (oh-toh-sklair-OH-sis)
• Defined
– A condition in which the footplate of the
stapes becomes immobile and secured to the
oval window, resulting in a hearing loss
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Careers
Allergist
Audiologist
Eye, Ear, Nose, and Throat Specialist
Ophthalmic Assistant
Ophthalmic laboratory technician
Ophthalmic medical technologist
Ophthalmic technician
Ophthalmologist
Optician
Optometrist
Optometrist
Otolaryngologist
Otolaryngologist
Otologist
Medical Terms
Root word: dacry(o) – denoting tears
or lacrimal (tear) glands or ducts
• Dacryo aden itis
inflammation of
gland
• Dacryostenosis
narrowing
• Dacryo lith iasis
stone,concretion,condition
• Dacryocyst
sac
• Dacryorrhea
flowing
Medical Terms
Root word: irid(o) – denotes a
relationship to the iris of the eye
• Iridectasis
enlargement
• Iridomalacia
• Iridotomy
• Iritis
• Iridoplegia
dilatation,
softening
incision
inflammation
paralysis
Medical Terms
Root word: kerat,kerat(o) – denoting
the cornea of the eye or horny tissue
• Keratiasis
disease condition
• Keratoderma skin
• Keratoid
like, resemble
• Keratosis
condition, disease
process
• Keratoma
tumor, growth
Medical Terms
Root word: ophthalm(o) –
denoting the eye
• Ophthalmoplegia stroke, paralysis
• Ophthalmology study of, science of
• Ophthalmoscope viewing
instrument
• Ophthalmometer measure
• Ophthalmomalacia soft, softening
Medical Terms
Root word: blephar(o) – denoting
the eyelid
• Blepharorrhaphy
• Pachyblepharon
• Blepharitis
• Blepharoplasty
• Blepharoptosis
drooping
suture
thick
inflammation
plastic surgery
falling or
Medical Terms
Root Word: kerat(o) – denoting
the cornea of the eye or horny
tissue
• Kerato myc osis fungus condition,
disease
• Keratoiritis
iris inflammation
• Keratocentesis puncture
• Keratoplasty
plastic surgery
• Keratocele
hernia
Medical Terms
Root word: ot(o) – form indicating
the ear
• Otitis
• Otalgia
• Otorrhea
• Otologist
• Otopyosis
disease
inflammation
pain
flowing, discharge
specialist
pus condition,
Abbreviation
P
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P
P
P
PA
PAC
PAP
Para
Path
Pb
PBI
Meaning
after
pulse, phosphorus
physician’s assistant
premature atrial contraction
Papanicolaou test (smear)
number of pregnancies
pathology
lead
protein-bound iodine
•P
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Abbreviation
P
Meaning
Pc
after meals
PCA
patient-controlled analgesia
PCC
poison control center
PCP
patient care plan
PCT
patient/personal care technician
PDR
Physicians’ Desk Reference
PE
physical examination, pulmonary edema
Peds
pediatrics
Per
by, through
PET
positron emission tomography
pH
measure of acidity/alkalinity
Pharm
Pharmacy
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Abbreviation
P
P
Meaning
PI
present illness
PID
pelvic inflammatory disease
PKU
phenylketonuria
pm
after noon
PMC postmortem (after death) care
PMS
premenstrual syndrome
PNS
peripheral nervous system
Po
by mouth
PO
phone order
Post
posterior, after
Post-op after an operation
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Abbreviation
P
P
Meaning
PP
postpartum (after delivery)
PPE personal protective equipment
PPO preferred provider organization
Pre-op before an operation
Prep
prepare
Prn
whenever necessary, as needed
Psy psychology, psychiatry
Pt
patient, pint (500ml or cc)
PT
Physical therapy/therapist
PTT partial thromboplastin time
PVC premature ventricular contraction
PVD peripheral vascular disease
Px
prognosis, physical examination