1. Chapter 17 Goals Page 697 Students will be able to:
Identify locations & functions of the major parts of the eye & ear.
Name the combining forms, prefixes, & suffixes most commonly used to describe these organs & their parts.
Describe the abnormal conditions that may affect the eye & the ear.
Identify clinical procedures that pertain to ophthalmology & otology.
Apply your new knowledge to understanding medical terms in their proper contexts, such as medical reports & records.

2. Sense Organs: The Eye & The Ear
Chapter 17
Pages 697 – 748

3. Introduction Page 698 The eye & the ear are sense organs.
They are receptors whose sensitive cells may be activated by a particular form of energy or stimulus in the external or internal environment.
The sensitive cells in the eye & ear respond to the stimulus by initiating a series of nerve impulses along sensory nerve fibers that lead to the brain.

4. Introduction: Cont. Page 698
No matter what stimulus affects a particular receptor, the resulting sensation in determined by regions in the brain connected to that receptor.
Thus, mechanical injury that stimulates receptor cells in the eye & ear may produce sensation of vision & sound.
If a workable connection could be made between the sensitive receptor cells of the ear & the area in the brain associated with sight, it would be possible to “see” sounds.
sensation of vision (flashes of light)
sensation of sound (ringing in the ears)

5. The Eye Page 698 Anatomy & Physiology
Pupil = central dark opening of the eye, where light rays enter.
Conjunctiva = a membrane lining the inner surfaces of the eyelids & anterior portion of the eyeball over the white of the eye. It is clear & almost colorless except when blood vessels are dilated.
Sclera = opaque white of the eye; a fibrous layer under the conjunctiva.
bloodshot eyes = Dust & smoke cause the blood vessels to dilate, giving the conjunctiva a reddish appearance
conjunctivitis = blood vessels dilate when the eye is infected or inflamed by allergies.
Sclera = It extends from the cornea on the anterior surface of the eyeball to the optic nerve in the posterior of the eye.

6. Page 698
The Eye: Cont.
Cornea = a fibrous, transparent tissue that extends like a dome over the pupil & iris. The function of the cornea is to bend, or refract, the rays of light so they are focused properly on the sensitive receptor cells in the posterior region of the eye. The normal, healthy cornea is avascular but receives nourishment from blood vessels near its junction the sclera.
Corneal transplants for people with scarred or opaque corneas are often successful because antibodies responsible for rejection of foreign tissue usually do not reach the avascular, transplanted corneal tissue.
avascular (has no blood vessels)

7. Pages 698 – 699
The Eye: Cont.
Uvea of the eye: the choroid, iris & ciliary body.
Iris = color portion of the eye; surrounds the pupil. Muscles of the iris constrict & dilate the pupil.
Choroid = dark brown membrane inside the sclera; contains many blood vessels.
Ciliary body = surrounds the outside of the lens in full circle. Fine, thread-like attachments connect the ciliary body & the lens, allowing the muscles in the ciliary body to adjust the shape & thickness of the lens. These changes in the shape of the lens cause refraction of light rays.
constrict the pupil in bright light & dilate the pupil in dim light.
Refraction = the bending of rays as they pass through the cornea, lens, & other tissues. Muscles of the ciliary body produce flattening of the lens (for distant vision) & thickening & rounding of the lens (for close vision). This refractory adjustment to focus on an object from far to near is called accommodation. When people get older, their eyes’ ability to accommodate decreases, they may need magnifying glasses to see close objects & to read.

8. Page 699
The Eye: Cont.
Besides regulating the shape of the lens, the ciliary body also secretes aqueous humor.
Aqueous humor = found in the anterior chamber of the eye; maintains the shape of the anterior of the eye & nourishes the structures there.
Vitreous chamber = a large region behind the lens filled with vitreous humor
Vitreous humor = a soft, jelly-like material, vitreous humor; maintains the shape of the eyeball & is not constantly re-formed.
Both the aqueous & the vitreous humors further refract light rays.
Aqueous humor = The fluid is constantly produced & leaves the eye through a canal that carries it into the bloodstream.
Vitreous humor = Its escape (due to trauma or surgical damage) may result in significant damage to the eye, leading to possible retinal damage & blindness.

9. Pages 700 – 701
The Eye: Cont.
Retina = the thin, delicate, & sensitive nerve layer of the eye. As light travels through the eye, it is refracted so that it focuses on sensitive receptor cells of the retina called the rods & cones.
Cones = about 6.5 million; function in bright levels of light & are responsible form color & central vision.
Rods = about 120 million; function at reduced levels of light & are responsible for peripheral vision & vision in dim light.
it is refracted (by the cornea, lens, & fluids),
3 types of cones, each stimulated by one of the primary colors in light (red, green, or blue). Most cases of color blindness affect either the green or the red receptors, so that the two colors cannot be distinguished from each other.
When light rays are focused on the retina, a chemical change occurs in the rods & cones, initiating nerve impulses that then travels from the eye to the brain via the optic nerve.

10. Pages 700 – 701
The Eye: Cont.
Optic disc = the region in the eye where the optic nerve meets the retina. Because there are no light receptor cell in the optic disc, it is known as the blind spot of the eye.
Macula = a small, oval, yellowish area adjacent to the optic disc. It contains a central depression called the fovea centralis, which is composed largely of cones & is the location of the sharpest vision in the eye. If a portion of the fovea or macula is damaged, vision is reduced & central-vision blindness occurs.
The fundus of the eye is the posterior, inner part that is visualized through the ophthalmoscope.

11. Errors of Refraction Pages 708 – 709 astigmatism
defective curvature of the cornea or lens of the eye
hyperopia
Farsightedness
myopia
Nearsightedness
presbyopia
Impairment of vision as a result of old age

12. Pathology – The Eye Pages 710 – 711 cataract
Clouding of the lens, causing decreased vision
chalazion
Small, hard, cystic mass on the eyelid
diabetic retinopathy
Retinal effects of diabetes mellitus include micro aneurysms, hemorrhages, dilation of the retinal veins, & neovascularization (new blood vessels form in the retina).
glaucoma
Increased intraocular pressure results in damage to the retina & optic nerve with loss of vision

13. Pathology – The Eye: Cont.
Pages 712 – 713
Pathology – The Eye: Cont.
hordelum (stye or sty)
Localized, purulent, inflammatory staphylococcal infection of a sebacous oil-producing gland in the eyelid
macular degeneration
Progressive damage to the macula area of the retina
nystagmus
Repetitive rhythmic movements of one or both eyes
retinal detachment
Two layers of the retina separate from each other
strabismus
Abnormal deviation of the eye

14. Clinical Procedures – The Eye
Pages 714 – 715
Clinical Procedures – The Eye
Diagnostic
fluorescein angiography
Intravenous injection of fluorescein (a dye) followed by serial photographs of the retina through dilated pupils
ophthalmoscopy
Visual examination of the interior of the eye
slit lamp microscopy
Examination of anterior ocular structures under microscopic magnification
visual acuity test
Clarity of vision is assessed
visual field test
Measurement of the entire scope of vision (peripheral & central).

15. Clinical Procedures – The Eye
Pages 716 – 717
Clinical Procedures – The Eye
Treatment
enucleation
Removal of the entire eyeball
keratoplasty
Surgical repair of he cornea
laser photocoagulation
Intense, precisely focused light beam creates an inflammatory reaction the seals retinal tears & leaky retinal blood vessels.
LASIK
Use of an excimer laser to correct errors of refraction (myopia, hyperopia, & astigmatism)

16. Clinical Procedures – The Eye: Cont.
Pages 716 – 717
Clinical Procedures – The Eye: Cont.
Treatment
phacoemulsification
Ultrasonic vibrations break up the lens; the pieces are then aspirated through the ultrasonic probe.
scleral buckle
Suture of a silicone band to the sclera over a detached portion of the retina

17. The Ear Page 718 Anatomy & Physiology
The ear can be divided into three separate regions: outer ear, middle ear, & inner ear.
Sound waves are received by the outer ear, conducted by the middle ear to special receptor cells in the inner ear. Where it is then transmitted to nerve fibers that lead to the auditory region of the brain in the cerebral cortex. Sensations of sound are perceived within the nerve fibers of the cerebral cortex.

18. The Ear: Cont. Page 718 Outer Ear
Sound waves enter the ear through the pinna, or auricle, which is the projection part, or flap of the ear.
The external auditory meatus (auditory canal) leads from the pinna & is lined with numerous glands that secrete a yellow brown, waxy substance called cerumen.
Cerumen lubricates & protects the ear canal.

19. The Ear: Cont. Pages 718 – 719 Middle Ear
Sound waves travel through the auditory canal & strike a membrane between the outer & middle ear. This is the tympanic membrane, or eardrum. As the eardrum vibrates, it moves three small bones, or ossicles, that conduct the sound waves through the middle ear. These bones, in the order of their vibration, are the malleus, the incus, & the stapes. As the stapes moves, it touches a membrane called the oval window, which separates the middle from the inner ear.

20. Pages 718 – 719
The Ear: Cont.
Before proceeding with the pathway of sound conduction & reception into the inner ear, an additional structure that affects the middle ear should be mentioned.
Auditory (eustachian) tube = a canal leading from the middle ear to the pharynx. It normally is closed but opens on swallowing. This tube prevents damage to the eardrum & shock to the middle & inner ears.
Normally the pressure of air in the middle ear is equal to the pressure of air in the external environment; however, if you ascend in the atmosphere, as in flying in an airplane, climbing a high mountain, or riding a fast elevator, the atmospheric pressure, along with that in the outer ear, drops, while the pressure in the middle ear remains the same – greater than in the outer ear. This inequality of air pressure on the inside & outside of the eardrum forces the eardrum to bulge outward & potentially burst if the difference in pressures increases. Swallowing opens the eustachian tube so that air can leave the middle ear & enter the throat until the atmospheric & middle ear pressures are balanced. The eardrum then relaxes, & the danger of its bursting is averted.

21. The Ear: Cont. Page 719 Inner Ear (labyrinth)
Cochlea = leads from the oval window; it’s a bony, snail shell-shaped structure & contains special auditory liquids called perilymph & endolymph. The cochlea also contains a sensitive auditory receptor area called the organ of Corti.
In the organ of Corti, tiny hair cells receive vibrations from the auditory liquids & relay the sound waves to the auditory nerve fibers, which end in the auditory center of the cerebral cortex.
Labyrinth = because of its circular, mazelike structure.

22. Page 720
The Ear: Cont.
The ear is also important for equilibrium (balance).
The vestibule connects the cochlea to three semicircular canals. The semicircular canals contain a fluid, endolymph, as well as sensitive hair cells. In an intricate manner, the fluid & hair cells fluctuate in response to the movement of the head. This sends impulses to the brain. Messages are then sent to muscles in all parts of the body to ensure that equilibrium is maintained.

23. Pathology – The Ear Page 724 acoustic neuroma
Benign tumor arising from the acoustic vestibulocochlear nerve (eighth cranial nerve) in the brain
cholesteatoma
Collection of skin cells & cholesterol in a sac within the middle ear
deafness
Loss of the ability to hear
Meniere disease
Disorder of the labyrinth of the inner ear; elevated endolymph pressure within the cochlea (cochlear hydrops) & semicircular canals (vestibular hydrops)

24. Pathology – The Ear Page 725 ottis media
Inflammation of the middle ear
otosclerosis
Hardening of the bony tissue of the middle ear
tinnitus
Sensation of noises (ringing, buzzing, whistling, booming) in the ears.
vertigo
Sensation of irregular or whirling motion either of oneself or of external objects

25. Clinical Procedures – The Ear
Page 726
Clinical Procedures – The Ear
audiometry
Testing the sense of hearing
cochlear implant procedure
Surgical insertion of a device that allows sensorineural hearingimpaired persons to understand speech
ear thermometry
Measurement of the temperatrue of the tympanic membrane by detection of infrared radiation from the eardrum
otoscopy
Visual examination of the ear canal with an otoscope
tuning fork test
Test of ear conduction using a vibration source (tuning fork)