Chapter 11 Special Sense - The Eyes and Ears PDF

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Chapter 11 for EHS 115...

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● Functions Of The Eyes ○ Receive images and transmit them to the brain. ● Structures Of The Eyes ○ The Adnexa of the Eyes ■ Adnexa of the eyes (adnexa oculi) = structures outside the eyeball; includes the orbit, eye muscles, eyelids, eyelashes, conjunctiva, and lacrimal apparatus. ● Adnexa = the accessory or adjoining anatomical parts of an organ ■ Eye muscles = 6 major muscles, which are arranged in three pairs and are attached to each eye. ■ Binocular vision = occurs when the muscles of both eyes work together in coordination to make normal depth perception possible. ● Depth perception → ability to see in three dimensions ■ Upper and lower eyelids with eyebrows and eyelashes = help protect the eyeball from foreign matter, excessive light, and injuries due to other causes. ● Canthus = the angle where the upper and lower eyelids meet (canth → corner of the eye) ● Cilia = small hairs that make up the eyebrows and eyelashes; also present in the nose to prevent foreign matter from being inhaled. ● Tarsus (tarsal plate) = the framework within the upper and lower eyelids that provides the necessary stiffness and shape (tars → edge of the eyelid) ■ Conjunctiva = the transparent mucous membrane that lines the underside of each eyelid and continues to form a protective covering over the exposed surface of the eyeball. ■ Lacrimal apparatus (tear apparatus) = consists of the structures that produce, store, and remove tears. ● Lacrimal glands = secrete lacrimal fluid (tears); located on the underside of the upper eyelid just above the outer corner of each eye.

● Lacrimal fluid (tears) = maintains moisture on the anterior surface of the eyeball; blinking distributes the lacrimal fluid across the eye. ● Lacrimal canal = consists of a duct at the inner corner of each eye which collects tears and empties them into the lacrimal sacs; crying is the overflowing of tears from the lacrimal canals. ● Lacrimal sac (tear sac) = an enlargement of the upper portion of the lacrimal duct. ● Lacrimal duct (nasolacrimal duct) = the passageway that drains excess tears into the nose. ○ The Eyeball ■ Eyeball (globe) → 1-inch sphere with only about one-sixth of its surface visible. ● Optic = pertaining to the eye or sight (opt → vision) ● Ocular = pertaining to the eye (ocul → eye) ● Extraocular = outside the eyeball ● Intraocular = within the eyeball ■ Sclera (white of the eye) = maintains the shape of the eye and protects the delicate inner layers of tissue; this tough, fibrous tissue forms the outer layer of the eye, except for the part covered by the cornea. ■ Choroid (choroid coat) = the opaque middle layer of the eyeball that contains many blood vessels and provides the blood supply for the entire eye. ■ Retina = the sensitive innermost layer that lines the posterior segment of the eye; receives nerve impulses and transmits them to the brain via the optic nerve. ■ Aqueous humor (aqueous fluid) = fills the anterior and posterior chambers; helps the eye maintain its shape and nourishes the intraocular structures.

■ Intraocular pressure (IOP) = a measurement of the fluid pressure inside the eye; this pressure is regulated by the rate at which aqueous humor enters and leaves the eye. ■ Posterior segment = makes up the remaining two-thirds of the eyeball; is lined with the retina and filled with vitreous humor. ■ Vitreous humor (vitreous gel) = soft, clear, jelly-like mass that contains millions of fine fibers; these fibers are attached to the surface of the retina and help the eye maintain its shape. ■ Rods and cones = are located in the retina; receive images that have passed through the lens of the eye and are converted into nerve impulses and transmitted to the brain via the optic nerve; rods are the black and white receptors, and cones are the color receptors. ■ Macula (macula lutea) = the clearly defined light-sensitive area in the center of the retina that is responsible for sharp central vision. ■ Fovea centralis = a pit in the middle of the macula; color vision is best in this area because it contains a high concentration of cones and no rods. ■ Optic disk (blind spot) = small region in the eye where the nerve endings of the retina enter the optic nerve; does not contain any rods or cones. ■ Optic nerve = transmits nerve impulses from the retina to the brain ○ The Uvea ■ Uvea = the pigmented layer of the eye; has a rich blood supply and consists of the choroid, ciliary body, and iris. ■ Ciliary body = located within the choroid; is a set of muscles and suspensory ligaments that adjust the thickness of the lens to refine the focus of light rays on the retina. ■ Iris = colorful circular structure that surrounds the pupil; muscles within the iris control the amount of light that is allowed to enter the eye through the pupil. ● To decrease the amount of light entering the eye, the muscles of the iris contract, making the opening of the pupil smaller.

● To increase the amount of light entering the eye, the muscles of the iris relax, or dilate, making the opening of the pupil larger. ■ Cornea = the transparent outer surface of the eye covering the iris and pupil; is the primary structure focusing light rays entering the eye. ■ Pupil = the black circular opening in the center of the iris that permits light to enter the eye. ■ Lens = clear, flexible, curved structure that focuses images on the retina ○ Normal Action of the Eyes ■ Accommodation = process where the eyes make adjustments for seeing objects at various distances; adjustments include contraction (narrowing) and dilation (widening) of the pupil, movement of the eyes, and changes in the shape of the lens. ■ Convergence = the simultaneous inward movement of the eyes toward each other. ■ Emmetropia = the normal relationship between the refractive power of the eye and the shape of the eye that enables light rays to focus correctly on the retina (emmetr → in proper measure; -opia → vision condition) ■ Refraction (refractive power) = ability of the lens to bend light rays so they focus on the retina. ■ Visual acuity = ability to distinguish object details and shape at a distance. ● Acuity → sharpness ● Medical Specialties Related To The Eyes And Vision ○ Ophthalmologist = physician who specializes in diagnosing and treating the full spectrum of diseases and disorders of the eyes, from vision correction to eye surgery (ophthalm → eye) ○ Optometrist = holds a doctor of optometry degree and provides primary eye care, including diagnosing eye diseases and conditions and measuring the

accuracy of vision to determine whether corrective lenses are needed (opt/o → vision) ○ Optician = a health care practitioner who designs, fits, and dispenses lenses for vision correction. ● Pathology Of The Eyes And Vision ○ The Eyelids ■ Ptosis = the drooping of the upper eyelid that is usually due to paralysis (ptosis → drooping or sagging) ■ Chalazion = a nodule or cyst, usually on the upper eyelid, caused by obstruction in a sebaceous gland. ■ Hordeolum (stye) = pus-filled and often painful lesion on the eyelid resulting from an acute infection in a sebaceous gland. ■ Blepharitis = swelling of the eyelid, often at the location of the eyelash hair follicles (blephar → eyelid) ■ Ectropion = eversion of the edge of an eyelid (eversion → turning outward) ■ Entropion = inversion of the edge of an eyelid (inversion → turning inward) ■ Periorbital edema = swelling of the tissues surrounding the eye or eyes ○ Additional Adnexa Pathology ■ Conjunctivitis (pinkeye) = inflammation of the conjunctiva that is usually caused by an infection or allergy. ■ Dacryoadenitis = inflammation of the lacrimal gland caused by a bacterial, viral, or fungal infection (dacry/o → tear) ■ Subconjunctival hemorrhage = bleeding between the conjunctiva and the sclera. ■ Xerophthalmia (dry eye) = drying of eye surfaces, including the

conjunctiva, because the tear glands do not produce enough tears (xer → dry) ○ Uvea, Cornea, Iris, and Sclera ■ Uveitis = inflammation of the uvea causing swelling and irritation; complications from uveitis can potentially lead to permanent vision loss. ■ Iritis = most common form of uveitis; this inflammation of the uvea affects primarily structures in the front of the eye (ir → iris); has a sudden onset and may last six to eight weeks. ■ Corneal abrasion = an injury, such as a scratch or irritation, to the outer layers of the cornea. ■ Corneal ulcer = a pitting of the cornea caused by an infection or injury; although these ulcers heal with treatment, they can leave a cloudy scar that impairs vision. ■ Diabetic retinopathy = damage to the retina as a complication of uncontrolled diabetes. ■ Keratitis = inflammation of the cornea (kerat → cornea); can be due to many causes, including bacterial, viral, or fungal infections. ■ Keratoconus = occurs when the cornea becomes irregular and coneshaped, causing blurring and distortion of vision. ■ Scleritis = inflammation of the sclera; usually associated with infections, chemical injuries, or autoimmune diseases. ○ The Eye ■ Anisocoria = condition in which the pupils are unequal in size (anis/o → unequal size); can be congenital or caused by a head injury, an aneurysm, or pathology of the central nervous system. ■ Cataract = the loss of transparency of the lens that causes a progressive loss of visual clarity; the formation of most cataracts is associated with aging; however, this condition can be congenital or due to an injury or disease.

■ Floaters (vitreous floaters) = particles of cellular debris that float in the vitreous humor and cast shadows on the retina. ■ Photopsia = the presence of what appears to be flashes of light, or flashers (phot → light); often caused by damage to the eye or migraine headaches. ■ Miosis = the contraction of the pupil, normally in response to exposure to light but also possibly due to the use of prescription or illegal drugs (mio → smaller) ■ Mydriasis = the dilation of the pupil, is the opposite of miosis; causes of mydriasis include diseases, trauma (injury), and drugs. ■ Nystagmus = an involuntary, constant, rhythmic movement of the eyeball that can be congenital or caused by a neurological injury or drug use. ■ Papilledema (choked disk) = swelling and inflammation of the optic nerve at the point of entrance into the eye through the optic disk (papill → nipple-like); caused by increased intracranial pressure and can be due to a tumor pressing on the optic nerve. ■ Retinal detachment (detached retina) and retinal tears = the separation of some or all of the light-sensitive retina from the choroid; if not treated, the entire retina can detach, causing blindness; can be caused by head trauma, aging, or the vitreous humor separating from the retina. ■ Retinitis pigmentosa = progressive degeneration of the retina that affects night and peripheral vision; can be detected by the presence of dark pigmented spots in the retina. ■ Glaucoma = group of diseases characterized by increased intraocular pressure that causes damage to the retinal nerve fibers and the optic nerve; this increase in pressure is caused by a blockage in the flow of fluid out of the eye; if untreated, this pressure can cause the loss of peripheral vision and eventually blindness. ● Open-angle glaucoma (chronic glaucoma) = most common form; the trabecular meshwork gradually becomes blocked, causing a

buildup of pressure. ● Closed-angle glaucoma (acute glaucoma) = the opening between the cornea and iris narrows so that fluid cannot reach the trabecular meshwork; this narrowing causes an increase in intraocular pressure that produces severe pain, nausea, redness of the eye, and blurred vision. ■ Macular degeneration = gradually progressive condition in which the macula at the center of the retina is damaged, resulting in the loss of central vision but not in total blindness (macul → spot) ○ Functional Defects ■ Diplopia (double vision) = the perception of two images of a single object ■ Hemianopia = blindness in one-half of the visual field ■ Monochromatism (color blindness) = inability to distinguish certain colors in a normal manner; genetic condition caused by deficiencies in or the absence of certain types of cones in the retina. ■ Nyctalopia (night blindness) = condition in which an individual with normal daytime vision has difficulty seeing at night (nyctal → night) ■ Photophobia = excessive sensitivity to light and can be the result of migraines, excessive wearing of contact lenses, drug use, or inflammation. ■ Presbyopia = condition of common changes in the eyes that occur with aging; with age, near vision declines noticeably as the lens becomes less flexible and the muscles of the ciliary body become weaker; result is that the eyes are no longer able to focus the image properly on the retina. ■ Strabismus = disorder in which the eyes point in different directions or are not aligned correctly, because the eye muscles are unable to focus together. ● Esotropia (cross-eyes) = strabismus characterized by an inward deviation of one or both eyes (eso → inward) ● Exotropia (walleye) = strabismus characterized by the outward deviation of one eye relative to the other (exo → outward)

○ Refractive Disorders ■ Refractive disorder = a focusing problem that occurs when the lens and cornea do not bend light so that it focuses properly on the retina. ● Ametropia = any error of refraction in which images do not focus properly on the retina (ametr → out of proportion); astigmatism, hyperopia, and myopia are all forms of ametropia. ● Astigmatism = condition in which the eye does not focus properly because of uneven curvatures of the cornea. ● Hyperopia (farsightedness) = defect in which light rays focus beyond the retina; can occur in childhood but usually causes difficulty after age 40. ● Myopia (nearsightedness) = defect in which light rays focus in front of the retina; occurs most commonly around puberty. ○ Blindness ■ Blindness → inability to see ● Legal blindness → the point at which, under law, an individual is considered to be blind. ■ Amblyopia = a dimness of vision or the partial loss of sight, especially in one eye, without detectable disease of the eye (ambly → dim or dull) ■ Scotoma (blind spot) = an abnormal area of diminished vision surrounded by an area of normal vision. ● Diagnostic Procedures For Vision And The Eyes ○ Diagnostic Procedures for Vision ■ Snellen chart (SC) = used to measure visual acuity; results for each eye are recorded as a fraction with 20/20 being considered normal. ■ Refraction test = determines an eye's refractive error so that the best corrective lenses can be prescribed. ■ Diopter = the unit of measurement of a lens's refractive power

■ Cover test = an examination of how the two eyes work together and is used to assess binocular vision; one eye at a time is covered while the patient focuses on an object across the room. ■ Visual field testing (perimetry) = performed to determine losses in peripheral vision; this test is done by having the patient look straight ahead and indicate whether or not they can see an object or flash of light when it is presented in their periphery. ○ Diagnostic Procedures for the Eyes ■ Ophthalmoscopy (funduscopy) = the use of an ophthalmoscope to visually examine the fundus (back part) of the eye; this examination includes the retina, optic disk, choroid, and blood vessels. ■ Dilation = is required in preparation for the ophthalmoscopic examination of the interior of the eye; artificial enlargement of the pupils is achieved through the use of mydriatic drops. ■ Mydriatic drops = are placed into the eyes to produce temporary paralysis, forcing the pupils to remain dilated even in the presence of bright light. ■ Slit-lamp ophthalmoscopy = diagnostic procedure in which a narrow beam of light is focused onto parts of the eye to permit the ophthalmologist to examine the structures at the front of the eye, including the cornea, iris, and lens; fluorescein staining is used to help detect foreign bodies or an infected or injured area of the eye. ■ Fluorescein staining = the application of fluorescent dye to the surface of the eye via eye drops or a strip applicator; this dye causes a corneal abrasion to temporarily appear bright green. ■ Fluorescein angiography = radiographic study of the blood vessels in the retina of the eye following the intravenous injection of a fluorescein dye as a contrast medium. ■ PERRLA = Pupils are Equal, Round, Responsive to Light and Accommodation; it is a diagnostic observation, and any abnormality here could indicate a head injury or damage to the brain.

■ Tonometry = the measurement of intraocular pressure (ton/o → tension) ● Treatment Procedures Of The Eyes And Vision ○ The Orbit and Eyelids ■ Orbitotomy = surgical incision into the orbit (orbit → bony socket); is performed for biopsy, abscess drainage, or removal of a tumor or foreign object. ■ Tarsorrhaphy = the partial or complete suturing together of the upper and lower eyelids to protect the eye when the lids are paralyzed and unable to close normally. ○ The Conjunctiva and Eyeball ■ Corneal transplant (keratoplasty) = surgical replacement of a scarred or diseased cornea with clear corneal tissue from a donor. ■ Enucleation = the removal of the eyeball, leaving the eye muscles intact. ■ Ocular prosthesis (artificial eye) = may be fitted to wear over a malformed eye or to replace an eyeball that is either congenitally missing or has been surgically removed. ■ Iridectomy = surgical removal of a portion of the tissue of the iris; most frequently performed to treat closed-angle glaucoma. ■ Radial keratotomy = surgical procedure to treat myopia ■ Scleral buckle = a silicone band or sponge used to repair a detached retina. ■ Vitrectomy = the removal of the vitreous humor and its replacement with a clear solution; sometimes performed to treat a retinal detachment or when diabetic retinopathy causes blood to leak and cloud the vitreous humor. ■ Lensectomy = surgical removal of a cataract-clouded lens ■ Phacoemulsification = uses an ultrasonic vibration to shatter and remove the lens clouded by a cataract; it is performed through a very small opening, and the same opening is used to slide the intraocular lens into

place. ■ Intraocular lens (IOL) = a surgically implanted replacement for a natural lens that has been removed ○ Corrective Lenses ■ Concave lenses (curved inward) → used for myopia, or nearsightedness ■ Convex lenses (curved outward) → used for hyperopia, or farsightedness ■ Bifocals → lenses with two powers ■ Trifocals → lenses with three powers ■ Contact lenses → refractive lenses that float directly on the tear film in front of the eye. ○ Laser Treatments of the Eyes ■ Laser iridotomy = uses a focused beam of light to create a hole in the iris of the eye; performed to treat closed-angle glaucoma by creating an opening that allows the aqueous humor to flow between the anterior and posterior chambers of the anterior segment of the eye. ■ Laser trabeculoplasty = used to treat open-angle glaucoma by creating openings in the trabecular meshwork to allow the fluid to drain properly. ■ LASIK (Laser-Assisted in Situ Keratomileusis) = used to treat vision conditions, such as myopia, that are caused by the shape of the cornea; during this procedure, a flap is opened in the surface of the cornea, and then a laser is used to change the shape of a deep corneal layer. ■ Photocoagulation = use of a laser to treat some forms of wet macular degeneration by sealing leaking or damaged blood vessels; also used to repair small retinal tears by intentionally forming scar tissue to seal the holes. ■ Retinopexy = used to reattach the detached area in a retinal detachment ● Functions Of The Ears

○ Function: receive sound impulses and transmit them to the brain; the inner ear also helps maintain balance. ○ Auditory = pertaining to the sense of hearing ○ Acoustic = pertaining to sound or hearing ● Structures Of The Ears ○ The Outer Ear ■ Pinna (auricle/outer ear) = external portion of the ear; captures sound waves and transmits them into the external auditory canal. ■ External auditory canal = transmits these sound waves to the tympanic membrane (eardrum) of the middle ear. ■ Cerumen (earwax) = secreted by ceruminous glands that line the auditory canal; it traps sma...