Ch 20, 21- Ortho

9. What is the structure and function of the auditory system? • composed of the peripheral auditory system and the central auditory system

- central integrates and assigns meaning to what is heard and is composed of the vestibulocochlear nerve (CN VIII) and auditory cortex of the brain - peripheral includes the structures of the ear itself such as the external, middle, and the inner ear - it is concerned with the reception and perception of sound 1) external and middle: conduct and amplify sound waves from the outside environment via air conduction - issues in these portions of the ear cause conduction hearing loss which results in a decrease in sound intensity and or distortion in sound. 2) inner ear: has two organs called the semicircular canals (~serve as the body's balance organ) and the cochlea (~serves as the microphone which converts sound pressure impulses to the brain via auditory nerve) - disturbances cause impaired coordination, balance, and orientation - issues will cause sensorineural hearing loss which is the ability to understand speech or cause complete hearing loss. 2. What makes up the external ear? • auricle (pinna) is composed of cartilage and connective tissue covered with epithelium which lines the auditory canal - lined with cilia (~fine hairs), sebaceous (~oil), and ceruminous (~wax) glands - the oil and wax lubricate the ear canal which keeps it free from debris/bacteria • function of the external ear is to collect and transmit sound waves to the tympanic membrane (ear drum) which is a shiny, translucent, pearl-gray membrane that serves as an instrument of sound transmission. 3. What makes up the middle ear? • it is a space cavity (~with air) that is located in the temporal bone - mucous membranes lines the middle ear - continuous from the nasal pharynx via the eustachian tube • eustachian tube equalizes atmospheric air pressure between the middle ear and throat and allows the tympanic membrane to move freely. - normally closed and opened with movement of the jaw (~swallowing) - blockage can occur with allergies • contains the three smallest bones (~ malleus, incus, and stapes) - vibrations of the tympanic membrane cause them to move and transmit sound 4. What makes up the inner ear? • the inner ear contains a membrane with fluid filled inside called endolymph - debris such as loose crystals of calcium or excessive pressure within the lymphatic fluid can produce paroxysmal positional vertigo • contains the functional organs of hearing and balance - the receptor organ for hearing is called the cochlea - consists of the Organ of Corti which allows for transduction of sound vibration into neural signals 5. What is the transmission of sound? sound waves travel by air picked up by the auricles and auditory canal sound waves strike the tympanic membrane cause vibrations stapes moves back and forth sound waves are transmitted to the liquid of the inner ear picked up by tiny sensory hair cells of the cochlea initiates nerve impulses carried to the nerve fibers of the main branch of the acoustic portion of CN VIII brain 6. What is the assessment of the auditory system? • assessment should include assessment of hearing and equilibrium - vertigo is a sense that the person or objects around the movement of the head • dizziness is the sensation of being off balance with standing or walking - nystagmus is an abnormal eye movement that may be observed as a twitching of the eyeball or described by the patient as a blurring of vision • past history should include previous problems with the ears - frequency of acute middle ear infections - surgical procedures (~myringotomy) - perforations of the ear drum - drainage - history of mumps, measles, or scarlet fever - drugs during first trimester of pregnancy • records symptoms such as vertigo, tinnitus, and hearing loss in "patient's words" • information about past or present medications that are ototoxic (~antibiotics, birth controls, aspirin) Normal Physical Assessment of Auditory System • ears symmetric in location and shape • auricles and tragus nontender, without lesions - palpate auricle and mastoid areas for pain and tenderness - grasping the auricle or pressing on tragus can elicit pain • canal clear, tympanic membrane intact, landmarks and light reflex intact • able to hear low whisper at 30 cm • Weber test results = no lateralization Rinne test results air conduction > bone conduction - normal auditory intensity and strength is 0 to 110 dB (decibels) - normal speech = 40 to 65 dB - soft whisper = 20 dB Weber test 1. Stem of vibrating tuning fork is placed on midline of skull or forehead. 2. Patient asked to indicate where the sound is heard best. 3. In normal auditory function, the patient perceives a midline tone and the sound is heard equally in both ears. 4. If a patient has conductive hearing loss in one ear, the sound will be heard louder (lateralizes) in that ear. 5. If sensorineural loss is present, the sound is louder (lateralizes) in the normal (unaffected) ear. Rinne test 1. Hearing by bone conduction (BC) and air conduction (AC) is compared. 2. Stem of vibrating tuning fork held against mastoid bone (for BC of sound) and time noted. 3. When the sound is no longer perceived behind the ear (BC of sound), time is noted once again and the still-vibrating fork is moved close to the pinna (AC sound). 4. Have the patient report when the sound next to the ear canal (AC) is no longer heard and note time. 5. Normally, the sound is heard twice as long in front of the ear as it is on the bone. *With conductive hearing loss, the relationship is reversed

8. What are the

abnormalities? Description Possible Etiology and Significance Pain Foreign body sensation Superficial corneal erosion or abrasion. Can result from contact lens wear or trauma. Conjunctival or corneal foreign body Severe, deep, throbbing Anterior uveitis, acute glaucoma, infection. Acute glaucoma also associated with nausea, vomiting Photophobia Persistent abnormal intolerance to light Inflammation or infection of cornea or anterior uveal tract (iris and ciliary body) Blurred vision Gradual or sudden inability to see clearly Refractive errors, corneal opacities, cataracts, migraine aura, retinal changes (detachment, macular degeneration) Spots or Floaters Patient describes seeing spots, "spider webs," "curtain," or floaters within the field of vision Most common cause is vitreous liquefaction (benign phenomenon). Other possible causes include hemorrhage into the vitreous humor, retinal holes or tears. Dryness Discomfort, sandy, gritty, irritation, or burning Decreased tear formation or changes in tear composition because of aging or various systemic diseases Diplopia Double vision Abnormalities of extraocular muscle action related to muscle or cranial nerve pathologic condition Allergic Reactions Redness, excessive tearing, and itching of lid margins Many possible allergens. Associated eye trauma can occur from rubbing itchy eyelids. Hordeolum (sty) Small, superficial white nodule along lid margin Infection of sebaceous gland of eyelid. Causative organism is usually bacterial (most commonly Staphylococcus aureus). Blepharitis Redness, swelling, and crusting along lid margins Bacterial invasion of lid margins. Often chronic Ptosis Drooping of upper lid margin, unilateral or bilateral Mechanical causes as a result of eyelid tumors or excess skin. Myasthenia gravis Entropion Inward turning of upper or lower lid margin, unilateral or bilateral Congenital causes resulting in development abnormalities Ectropion Outward turning of lower lid margin Mechanical causes as a result of eyelid tumors, herniated orbital fat, or extravasation of fluid Conjunctivitis Redness, swelling of conjunctiva. May be itchy Bacterial or viral infection. May be allergic response or inflammatory response to chemical exposure Subconjunctival Hemorrhage Appearance of blood spot on sclera. May be small or can affect entire sclera Conjunctival blood vessels rupture, leaking blood into the subconjunctival space. Corneal abrasion Localized painful disruption of the epithelial layer of cornea. Can be visualized with fluorescein dye Trauma. overwear or improper fit of contact lenses Exophthalmos Protrusion of globe beyond its normal position within bony orbit. Sclera often visible above iris when eyelids are open Intraocular or periorbital tumors. Hyperthyroidism Anisocoria Pupils unequal (constricted) Central nervous system disorders. Slight difference in pupil size is normal in some people. Accomodation (abnormal) Pupils respond asymmetrically or abnormally to light stimulus or accommodation. Central nervous system disorders, general anesthesia Strabismus Deviation of eye position in one or more directions Overaction or underreaction of one or more extraocular muscles Cataract Opacification of lens. Pupil can appear cloudy or white when opacity is visible behind pupil opening. Aging, trauma, diabetes, long-term systemic corticosteroid therapy Peripheral Partial or complete loss of peripheral vision Glaucoma. Interruption of visual pathway (e.g., tumor). Migraine headache Central Loss of central vision Macular disease * arcus senilis or age-related degeneration of the cornea is considered a normal finding in the aging population *

17. What are the intraocular infections?

• a term used to describe inflammation of the uveal tract, vitreous body, optic nerve • caused by bacteria, viruses, fungi, or parasites - endophthalmitis: an extensive intraocular inflammation of the vitreous body - can be endogenous which the infecting agent arrives at the eye through the bloodstream - can be exogenous which involves the infecting agent to be introduced into a surgical wound or penetrating injury • can lead to irreversible blindness within hours or days • includes ocular pain, photophobia, headaches, reddened and swollen conjunctiva • treatment depends on the underlying cause - antimicrobial agents which are delivered topically, subconjunctivally, intravitreally, systemically, or in some combo.

24. What is otitis media with effusion?

• inflammation of the middle ear with a collection of fluid in the middle ear space - mucous can be thin, mucoid, or purulent pathology: • auditory tube can not open and allow equialization of atmospheric pressure than negative pressure within the middle ear pulls fluid from surrounding tissues - commonly follows upper respiratory tract and sinus infections clinical manifestations: • feeling of fullness of the ear • a "plugged" feeling or popping • decreased hearing • do not experience pain, fever, or discharge treatment: • antibiotics (~mouth or ear drops) • decongestants, antihistamines, nasal steroids • for chronic = ear tube may be necessary

7. What is keratoconjunctiviti s sica?

• it is a dry eye disorder that is a common complaint of older adults and individuals with systemic diseases such as slceroderma and systemic lupus erythematosus - caused by a decrease in the quality or quantity of the tear film corneal ulcer - complain of sand in the eye, worsens through the day - use of artificual tears or ointments such as cyclosporine ophtalmic emulsions which helps to incrase the eyes' natural ability to produce tears - Sjogren's syndrome = dry eyes with dry mouth

15. What is glaucoma?

• it is a group of disorders characterized by incrased IOP, optic nerve atrophy, and peripheral visual field loss • second leading cause of permenant blindness in the United States - typically are unaware of the condition - increases with age pathology: • a proper balance of between the rate of aqueous production (inflow) and the rate of the aqueous reabsorption (outflow) is essential to maintain IOP within normal limit - takes place in the angle (iris meets the cornea) • rate of inflow is greater than the rate of outflow = IOP increases above limits types: 1. primary open-angle glaucoma: the most common type when the outflow of the aqueous humor is decreased. - the drainage channels become clogged and damage the optic nerve 2. primary angle-closure glaucoma: due to a reduction in the outflow of the aqueous humor that results in a closure. - the lens bulges forward as a result - an acute attack can be precipitated by situations in which the pupil remains partially dilated long enough to cause acute rise in IOP - it is important to check drug records before administering medications clinical manifestations: • open-angle glaucoma = develops slowly without symptoms of pain or pressure - usually does not notice the gradual vision loss until it is compromised - eventually develops tunnel vision • angle-closure glaucoma = sudden excruciating pain in or around the eye, which is often accompanied by nause and vomiting - visually will see halo around lights, blurred vision, ocular redness diagnostic tests: • IOP is usually elevated - measurements are repated over time to verify - open-angle glaucoma = IOP pressure > 22 and 32 mm Hg - angle-closure glaucoma = IOP pressure > 50 mm Hg - central vision may be decreased which causes "optic disc cupping" chronic open-angle glaucoma drug therapy (see below) • initial therapy is with medications • the patient must understand the importance of continued treatment and supervision • there is no cure for glaucoma! • β-Adrenergic blockers • α-Adrenergic agonists • cholinergic agents (miotics) - educate patients about decreased visual acuity especially in dim lighting • carbonic anhydrase inhibitors surgical therapy • argon laser trabeculoplasty (ALT) - non-invasive option to lower IOP when medications are not successful - laser stimulates scarring and contraction of the meshwork which opens the outflow channels - reduces IOP most of the time it is done - corticosteroids are given for 3 to 5 days after - most common complication = acute rise in IOP (~normal) • trabeculectomy with or without filtering implant - a surgical procedure which lowers the IOP inside the eye - makes a small hole in the eye acute angle-closure glaucoma • ocular emergency! • topical cholinergic agent • hyperosmotic agent • laser peripheral iridotomy • surgical iridectomy - used for long-term treatment and prevention of subsequent episodes - allow the aqueous humor to flow through a newly created opening in the iris and into the new outflow channels education • stress the importance of early detection and prevention - current recommendation is every 2 to 4 years between 40 and 64 years - every 1 to 2 years for people age 65 and older • stress the importance of therapeutic regimen and follow-up appointments • encourage adherence by helping identify the most convenient times

11. What are cataracts?

• it is an opacity within the lens which can be in one or both eyes pathology: • most are related to senile cataracts which is a age-related factor - altered metabolic process within the lens which causes accumulation of water - affects the lens transparency • blunt or penetrating trauma, maternal rubella, radiation or ultraviolet light, drugs clinical manifestations: • decrease in vision that is gradual • abnormal color perception and glare (due to light scatter via opacities) diagnosis: • based on decreased visual acuity and opacity is directly observable (~white pupil) non-surgical therapy • change in glasses prescription • strong reading glasses or magnifiers • increased lighting • lifestyle adjustment surgical therapy preoperative • appropriate physical and history evaluation • mydriatic, cycloplegic agents - produces pupillary dilation by contraction of the iris dilator muscle • cycloplegic agents - anticholinergic that produces paralysis of accommodation by blocking the effect of acetylcholine on the sphincter muscle - tropicamide (Mydriacyl and Tropicacyl) - instruct the patient to wear dark glasses to minimize photophobia - monitor for signs of systemic toxicity (~tachycardia) • nonsteroidal anti-inflammatory drugs • topical antibiotics • antianxiety medications surgery • removal of lens • Phacoemulsification - most common form of cataract surgery - a small incision is made in the surface of the eye in or near cornea - thin ultrasound probe is inserted into the eye - ultrasonic ultrasound vibrations are used to dissolve the clouded lens into fragments - pieces are then suctioned out - incisions are self-sealing and do not require sutures • extracapsular extraction - very advanced cataracts where the lens is too dense to dissolve into fragments - requires a larger incision for the cataract to be removed in one piece - sutures are required to close the larger wound - visual recovery is often slower • correction of surgical aphakia • intraocular lens implantation (most common) - almost all patients have an IOL implanted at the time of surgery - lens is implanted in the capsular bag behind the iris postoperative • usually go home as soon as the effects of sedation have worn off • topical antibiotic, topical corticosteroid, anti-inflammatory agent, analgesics - eye drops are gradually reduced in frequency and finally discontinued when the eye has healed - photophobia is common with use of pupil dilators -decrease room lighting • eye patch or shield and activity as prescribed by patient's surgeon -educate the patient that they will not have depth perception until patch is removed • educate patient to avoid activities that increase IOP (~bending, stooping, coughing, lifting) • notify health care provider if increased pain, hemorrhage, purulent drainage, redness, or decrease in vision.

4. What are the extraocular disorder?

(inflammation + infection) • one of the most common eye conditions is inflammation or infection of the external eye which are mainly caused by irritants or microorganisms types: • hordeolum: commonly referred to as a "sty" which is an infection of the sebaceous glands in the lid margin. - the most common bacterial infective agent = S. Aureus - red swollen, circumscribed, and acutely tender area develops rapidly - apply warm moist compresses 3-4x per day until improvement • chalazion: a chronic inflammatory granuloma of the sebaceous glands in the lid - slowly developing "lump" that forms due to blockage and swelling - generally not an infection - appears on the upper lid as a swollen, tender, reddened area that can be painful - use of warm compresses - if not effective - may drain the lesion or inject with corticosteroids • blepharitis: common chronic bilateral inflammation of the lid margins which it usually involves the part of the eyelid where the eyelashes grow. - lids are red rimmed with many scales or crusts on the lid margins/lashes - when tiny oil glands located near the base of the eyelashes become clogged - primary complain of itching - can experience burning, irritation, and photophobia - caused by a staph infection and is treated with ophthalmic antibiotic ointment - emphasize thorough cleaning hygiene

7. What is important to know for the subjective data? • past health history: specifically about systemic diseases such as hypertension, diabetes, rheumatoid arthritis, hypothyroidism, hyperthyroidism

- it is important to ask any history of cardiac or pulmonary disease due to the use of Beta Blockers which are often used to treat glaucoma - these medications slow heart rate, decrease BP, and increase asthma • date of last visual exam • use of glasses or contacts (~care of the contacts) • any surgical procedures to the eye or brain • obtain information about allergies - allergies often cause eye symptoms such as burning, itching, watering, draining, and blurred vision • inquire about elimination patterns such as straining (~valsalva manuver) • eye pain is an important symptom to assess - if present, question the patient about treatment and response Normal Physical Assessment of Visual System • visual acuity 20/20 without diplopia. - legal blindness is best-corrected vision in the better eye of 20/200 or less • external eye structures symmetric and without lesions or any deformities • lacrimal apparatus nontender and without drainage • conjunctiva clear (~pink and moist) • sclera is white with fine blood vessels visible - may take on a yellowish hue in the older adult due to fat deposits - pale blue cast due to scleral thinning is seen in older adults with aging • PERRLA. - consensuality is when the pupil constricts in opposite eye with light shine • lens clear. • intact EOM - performed in a dark room using an "H" pattern - finger or object is held 10 to 12 inches of the patient's nose • optic disc margins sharp • retinal vessels without AV nicking (artery crossing a vein), without hemorrhages or spots

2. What is visual impairment? • describes vision that cannot be fully corrected by lenses, treatment, or surgeries

- ranges from low vision to the absence (~total blindness) • assess the patient for how long vision has been impaired - determine how the patient's visual impairment affects normal functioning - level of difficulty of performing certain tasks - reading a newspaper, writing a check, moving from one room to another types: • low vision: impaired vision that cannot be improved by conventional eyeglasses, contact lenses, medication, or surgery. • severe visual impairment: unable to read ordinary newspapers even with correction -may or may not be legally blind • legal blindness: refers to central vision acuity of 20/200 or less in the better eye with correction or a peripheral vision field of 20 or less. nursing care: • provide emotional support and direct care to the patient • introduce onself and another other people who approach the patient • say good-bye when leaving the patient • speak while facing the patient and head position that validates you are listening • sighted-guide technique: stand slightly in front and to one side of the patient as well as offer an elbow. - describe the environment to help orient the patient - "We're going through an open doorway and approaching two steps down" - help the patient sit by placing one of his or her hands on the seat of the chair • place objects on the tray table in a "clock" assembly • braille or audio books for reading • cane or guide dog for ambulation are appropriate for no functional vision • approach magnification: simple way to enhance the residual vision - recommend the patient sit closer or hold the book at a closer level - watch TV in black and white - use of felt tip markers - use of contrasting colors (~red strip at the edge of the steps or curbs) - large font sizes for letters and numbers * non-24 hour sleep/wake disorder a common problem that occurs in blind people which is when an individual's biologic clock fails to synchronize to a 24-hour day* - difficulty falling asleep or staying asleep at night - have an uncontrollable urge to sleep - can result in insomnia, excessive sleepiness, social and work consequences - melatonin is used to shift the circaidum clock earlier or later - Tasimelteon (Hetiloz) works by timing the sleep-wake cycle

5. What are the external structures and their function? • the eyebrows, eyelids, and eyelashes serve as an important role in protecting the eye which acts as a physical barrier to dust and foreign particles

- the upper and lower eyelids join at the medial and lateral canthi. - blinking of the upper eyelid distributes tears over the anterior surface which nourishes the surface cells • conjunctiva is a transparent mucous membrane that covers the inner surface of the eyelid and forms a "pocket" under each eyelid - glands secrete mucus and tears • sclera is composed of collagen fibers that are meshed together to form an opaque structure that is commonly known as "white of the eye" - is a tough shell that helps protect the intraocular structures • cornea is transparent and avascular and allows light to enter the eye • lacriminal glands provide secretions to make up the mucous, aqueous, and lipid layers of the tear film - this film moistens the eye and provides oxygen to the cornea

Chapter 21: Visual and Auditory Problems

1. What are the refractive errors? • refractive errors are the most common which is a problem with focusing light accurately onto the retina due to the shape of the eye - prevents light rays from converging into a single focus on the retina - it is a result of irregularities of the corneal curvature - major symptom is blurred vision - can be treated with corrective lenses (~eyeglasses or contact lenses) types: • myopia: or "nearsightedness" is an inability to accommodate distant objects - light rays are focused in front of the retina - excessive light refraction by the cornea or lens - abnormally long eye - most common type of refractive error with the eyes • hyperopia or "farsightedness" is the inability to accommodate near objects - light rays are focused behind the retina - requires the use of accommodation to focus light rays on the retina - abnormally short eye - does not have adequate focusing power • presbyopia: loss of accommodation associated with the aging process - generally occurs about age 40 - the lens becomes larger, firmer, and less elastic - results in the inability to focus on near objects • astigmatism: caused by irregular corneal curvature which causes the incoming light rays to be bent unequally. - light rays do not come to a single point of focus on the retina • aphakia: absence of the lens which is a rare condition - may be congenital or occur during removal or cataracts - lens that is injured is removed and replaced with a intraocular lens implant nonsurgical treatment: 1. corrective glasses: refractive errors can be modified by using the appropriate lens - glasses for presbyopia are often referred to as "reading glasses" because they are usually worn for seeing close (~can add correction such as myopia) 2. contact lenses: made from various plastic and silicone substances that are highly permeable to oxygen and have a high water content - this allows for increased wearing time with greater comfort - can be associated with microbial keratitis which is a severe life-threatening complication which is caused by poor hand cleaning, poor lens case hygiene surgical treatment: • designed to eliminate or reduce the need for eyeglasses or contact lenses and to correct refractive errors by changing the focus of the eye. - most common are laser surgery and IOL implantation 1. laser-assisted in situ keratomileusis (LASIK): used for patients with low to moderately high amounts of myopia or hyperopia with or without astigmatism - involves using a laser or surgical blade = create a flap in cornea - flap is folded back which exposes the "stroma" of the cornea - pulses from a computer laser vaporize a part of the stroma - flap is then repositioned without sutures 1(a). photorefractive keratectomy (PRK): indicated for low to moderate amounts of myopia or hyperopia with or with an astigmatism and insufficient corneal to be a candidate for Lasik - epithelium is the only thing removed - laser sculpts the cornea to correct the error 2. refractive intraocular lens (implant): option for patients with a high degree of myopia or hyperopia. - involves the removal of the patient's "natural lens" and an implantation of a IOL (~small plastic lens to correct the refractive error) 2(a). phakic intraocular lenses: which are referred to as "implantable contact lenses" and is used for higher degrees of myopia and hyperopia - implanted into the eye without removing the "natural lens" - placed in front of the eye's natural lens - leaves the natural lens in the eye to preserve the eye's ability for reading

4. What are the visual pathways? 1) fibers from the left field of both eyes form the left optic tract and travel to the left occipital cortex.

2) fibers from the right field of both eyes form the right optic tract and travel to the right occipital cortex.

16. What is the medication therapy for glaucoma?

Action Side Effects Nursing Considerations β-Adrenergic Blockers betaxolol (B etoptic) 1. β1 cardioselective blocker. 2. ↓ IOP 3. ↓ aqueous humor production Transient discomfort bradycardia heart block, pulmonary distress headache depression (rarely reported) Topical drugs. • Minimal effect on pulmonary and cardiovascular parameter • Contraindicated in patient with bradycardia, cardiogenic shock, or over cardiac failure levobunolol (Betagan) timolol maleate (Timoptic, Istalol) 1. β1 and β2 non-cardioselective blockers 2. ↓ IOP 3. ↓ aqueous humor production Transient ocular discomfort blurred vision photophobia bradycardia decreased BP bronchospasm headache depression • Topical drops. • Same as betaxolol. • These β2-blockers are also contraindicated in patients with asthma or COPD α-Adrenergic Agonists dipivefrin (Propine) 1. α- and β-adrenergic agonist 2.Converted to epinephrine inside the eye 3. ↓ aqueous humor production 4. enhances outflow facility Ocular discomfort and redness tachycardia hypertension • Topical drops • Contraindicated in patient with narrow- angle glaucoma. • Teach punctal occlusion if patient at risk for systemic reactions. epinephrine 1. Same as dipivefrin • Same as dipivefrin -can be more severe • Topical drops apraclonidine (Iopidine) brimonidine 1. α-Adrenergic agonists 2. ↓ aqueous humor production Ocular redness. Irregular heart rate • Topical drops. • Used to control or prevent acute post-laser IOP rise (used before and after) • Teach patient at risk of systemic reactions to occlude puncta latanoprost (Xalatan) travoprost bimatoprost (Lumigan) 1. prostaglandin F analogs Increased brown iris pigmentation ocular discomfort and redness dryness itching foreign body sensation Topical drops. • Teach patient to not exceed 1 drop per evening • Have patient remove contact lens 15 min beforehand Cholinergic Agents (Miotics) carbachol (Miostat) Isopto Carbachol) 1. Parasympathomimetic. 2. Stimulates iris sphincter contraction, causing miosis and opening of trabecular meshwork, facilitating aqueous outflow. Transient ocular discomfort, headache blurred vision decreased adaptation to dark syncope salivation dysrhythmias vomiting and diarrhea, hypotension • Topical drops. • Caution patient about ↓ visual acuity caused by miosis - particularly dimness pilocarpine (Isopto Carpine, Pilocar) 1. Parasympathomimetic. 2. Stimulates iris sphincter contraction, causing miosis and opening of trabecular meshwork, facilitating aqueous humor outflow Same as carbachol • Topical drops • Same as carbachol Carbonic Anhydrase Inhibitors Systemic acetazolamide (Diamox) dichlorphenamide (Daranide) methazolamide 1. ↓ Aqueous humor production Paresthesia, especially "tingling" in extremities. Hearing dysfunction/tinnitus Loss of appetite/taste alteration, GI disturbances. Drowsiness, confusion • Oral non-bacteriostatic sulfonamides. • Anaphylaxis and other sulfa- type allergic reactions may occur in patient allergic to sulfa type drugs • Diuretic effect can ↓ electrolyte levels. • Should not be given to patient on high doses of aspirin therapy Topical brinzolamide (Azopt) dorzolamide (Trusopt) Transient stinging, blurred vision, redness Same as above

8. What is strabismus?

a condition in which the patient cannot consistently focus on the same object - may be caused by thryoid disease, problems with the eye muscles, retinal detachment, or cerebral lesions - an eye can deviate in = esotropia, out = exotropia, up = hypertropia and can deviate down = hypotropia - primary complaint is double vision

1. What is the structure and function of the visual system? • consists of the external tissues and structures surrounding the eye, internal structures of the eye, refractive media, and visual pathway to the brain.

a) external structures: eyebrows, eyelids, eyelashes, lacrimal system, conjunctiva, cornea, sclera, and extraocular muscles b) internal structures: iris, lens, ciliary body, choroid, and retina • refraction: light reflected from an object in the field of vision which passes passes through the transparent structures of the eye - light is "bent" so that a clear image can fall on retina - retina = the visual stimuli travel through the visual pathway to occipital cortex - perceptions of image

2. What are the structures and functions of vision? 1) globe or eyeball is composed of three layers

a) outer layer = sclera and transparent cornea b) middler layer = iris, choroid, and ciliary body c) innermost layer = retina 2) anterior cavity is composed of two compartments respectively a) anterior chamber = lies between the cornea and the iris b) posterior chamber = lies between the iris and the lens 3) aqueous humor is a clear watery fluid that fills the anterior and posterior chambers of the anterior cavity of the eye • prodcued from the capillary blood in the ciliary body • bathes and nourishes the lens and endothelium of the corena • excess production or decreased outflow can elevate intraocular pressure - normal pressure in the eye is 10 to 21 mm Hg 4) lens a biconvex structure located behind the iris and is supported by small fibers collectively called the "suspensory ligament". • primary function is to bend light rays allowing rays to fall onto retina • shape is modified by action of the ciliary body (~accomodation) 5) vitreous humor is a transparent gel-like substance that fills the posterior cavity. • light passing through may be blocked by nontransparent substance

7. What are the

abnormalities? Finding Description Possible Etiology and Significance Sebaceous Cyst (behind ear) Usually within skin, possible presence of black dot (opening to sebaceous gland) Removal or incision and drainage if painful Tophi Hard nodules in the helix or antihelix consisting of uric acid crystals Associated with gout, metabolic disorder. Further diagnosis needed Impacted Cerumen Wax that has not normally been excreted from the ear. No visualization of eardrum Decreased hearing possible, pain, sensation of fullness in auditory canal, removal necessary before otoscopic examination Discharge in Canal Infection of external ear, usually painful Swimmer's ear, infection of external ear. Possibly caused by ruptured eardrum and otitis media Swelling of Pinna (pain) Infection of glands of skin, hematoma caused by trauma Aspiration (for hematoma) Scaling or lesions Change in usual appearance of skin Seborrheic dermatitis, actinic keratosis, basal or squamous cell carcinoma Exostosis Bony growth extending into canal causing narrowing of canal Possible interference with visualization of tympanum. Usually asymptomatic Retracted eardrum Appearance of shorter, more horizontal malleus. Absent or bent cone of light Vacuum in middle ear, blockage of eustachian tube, negative pressure in middle ear Hairline Fluid Level (yellow- amber bubble fluid) Caused by transudate of blood and serum, meniscus of fluid producing hairline appearance Serous otitis media Bulging Ear Drum (blue or red) Fluid-filled middle ear, pus, blood Acute otitis media, perforation possible Perforation of Eardrum Previous perforations of the eardrum that have failed to heal. Thin, transparent layer of epithelium surrounding eardrum Chronic otitis media, mastoiditis, drainage Recruitment Perception that sounds are getting too loud too fast Sensorineural hearing loss. Hearing aid difficult to use

29. What is conductive hearing loss and sensorineural hearing loss?

conductive loss: • occurs when conditions in the outer or middle ear impair the transmisson of sound through air to the inner ear. - a common cause is otitis media with effusion - other causes = impacted cerumen, perforation of the tympanic membrane • audiogram demeonstrates better hearing through bone conduction than air • patient often speaks softly because his or her voice is louder • first step is identify and treat the cause • correction = hearing aid can help if loss is greater than 40 to 50 dBs sensorneural loss: • caused by impairment of function of the inner ear or the vestibulocochlear nerve - can be congential and hereditary factors, noise traum, aging, drugs • ototoxic drugs include aspirin, NSAIDs, antibiotics, loop diuretics, chemo agents • main problems = ability to hear sound but not to understand speech - diminished ability to hear high-pitched sounds - sound is muffled and difficult to understand clinical manifestations: • answering questions inappropriately • not responding when not looking at the person speaking • asking others to speak up • cupping the hand around the ear • increased sensitivity to slight increases in noise level • sudden hearng loss - often called the "unseen handicap" due to difficulty with communication - use of descriptive visual aids, sign language interpreter - maintain eye contact - use of therapeutic touch - speak normally and slowly - do not shout health promotion: • promote childhood and adult immunizations such as MMR vaccine • monitor for otoxicity when using otoxic drugs (~tinnitus, diminshed hearing) • use of hearing aids - gradually increase the noise (~start at home with few people talking) - store in a dry cool area • cochlear implant is a small complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or hard-of-hearing - full implantable device (~surgically place with nothing externally) - partial implantable device (~have an internal device as well as external device)

28. What is acoustic neuroma?

pathology: • a unilateral benign tumor that develops on the balance (~vestibular) and hearing or auditory (~cochlear) nerves leading from your inner ear to the brain. - branches of this nerve directly influence your balance and hearing - pressure on the nerve from the tumor may cause hearing loss and imbalance • early diagnosis = a tumor can compress the trigeminal and the facial nerves clinical manifestations: • hearing loss which is usually gradual • ringing in the affected ear • unsteadiness (~loss of balance) • facial numbness (~weakness or loss of muscle movement) diagnostic tests: • audiometry (~hear sounds directed to one ear at a time) - presents ranges of sounds of various sounds - indicate each time you hear sound • MRI - helps to identify the tumor interventions: • surgery to remove small tumors = preserves hearing - stereotactic radiosurgery can slow tumor growth and preserve facial nerve - large tumors (~3cm) - must report any signs of clear, colorless drainage from the ear

25. What is otosclerosis?

• a hereditary autosomal dominant disease which is the most common cause of hearing loss in young adults pathology: • spongy bone develops from the bony labyrinth which prevents movement of stapes - transmission of vibrations to the inner ear fluids reduces • one ear my show faster progression than the other clinical manifestations: • pain in one or both ears • drainage from the ear • muffled hearing diagnostic tests • history and physical examination • otoscopic examination - reveals a reddish blush of the tympanum (~Schwartz's sign) - caused by vascular and bony changes within middle ear • Rinne test - audiogram that demonstrates good hearing via bone conduction but poor air conduction (~air-bone gap) • Weber test • audiometry - difference of at least 20 to 25 dB between air and bone conduction • tympanometry management • hearing aid - amplification of sound can be effective • drug therapy - sodium fluoride with vitamin D along with calcium carbonate - these drugs retard bone reabsorption and encourage calcification of bony lesions • surgery (stapedectomy or stapes prosthesis)

12. What is retinopathy?

• a process of microvascular damage to the retina that can develop slow or rapidly - can lead to blurred vision and progressive vision loss - occurs most often in adults with diabetes or hypertension - experience spots or floaters, blurred vision, dark or empty areas of vision - "macular swelling" indicates a worsening of the condition which leads to intraretinal "dot or blot" hemorrhaging - severe central vision loss can result types: • diabetic retionpathy: common complication of diabetes with long-standing issues - nonproliferative retinopathy: most common form that is characterized by microaneurysms, retinal swelling, and hard exudates. - proliferative retinopathy: new blood vessels grow but are abnormal, fragile, and predisoposed to leak = causes severe vision loss • hypertensive retinopathy: caused by high BP creating blockages in retinal vessels - may not initially affect a person's vision - routine examinations reveal cotton-wood spots, retinal hemorrhages - can cause sudden loss of vision from swelling optic nerve = papilledema - treatment is focused on lowering the BP (~can restore vision) diabetic retinopathy hypertensive retinopathy proliferative retinopathy

13. What is retinal detachment?

• a separation of the sensory retina and the underlying epithelium with fluid that is accumulated between the two layers -almost all patients with an untreated symptomatic detachment become blind pathology: • the most common is retinal break which is an interruption in the full thickness of the retinal tissue. a) retinal holes: atrophic retinal breaks that occur spontaneously b) retinal tears: occur as the vitreous humor shrinks and pulls on the retina which results in a tear due to the force that exceeds the strength of the retina c) rhegmatogenous: once the retina has a break, the liquid vitreous can enter the subretinal space between the sensory layer. clinical manifestations: • photopsia which is "light flashes" • floaters or a "cobweb" or "hairnet" ring in the field of vision • painless loss of peripheral or central vision curtain coming across visual field • visual loss = corresponds to the area of detachment risk factors: • increasing age • severe myopia • eye trauma • family or personal history of retinal detachment diagnostic tests: • visual acutiy measurements are the first diagnostic procedure with any complaint surgical therapy: preoperative • mydriatic, cycloplegic agents • photocoagulation of retinal break that has not progressed to detachment surgeries • laser photocoagulation - seal retinal breaks by creating an inflammatory reaction that causes an adhesion or a scar to form - involves use of an intense, precisely focused light beam to create an inflammatory reaction - light is directed at the area of the retinal break • cryopexy - involves freezing (cryotherapy) the retinal break by placing a probe on the ocular surface at the location of the break - activated with compressed nitrous oxide gas that temporarily freezes break - freeze thaw reaction creates scarring in the area that will seal the break • scleral buckling procedure - indicated for significant detachment - involves indenting the globe so that the epithelium, choroid, and sclera move toward the sclera to buckle inward - may place an encircling band in case there are several breaks - subretinal fluid may be drained by inserting a small gauge needle • vitrectomy - surgical removal of the vitreous - used to relieve traction on the retina • intravitreal bubble - it is a intravitreal injection of a gas to form a temporary bubble in the vitreous that closes retinal breaks which provides separation of retinal layers - combined with laser photocoagulation postoperative • patient might be on bed rest with specific positioning • level of activity restriction varies which should be checked on doctor's order • topical antibiotic, topical corticosteroid, analgesics, and mydriatics

26. What is Meniere's Disease?

• also known as "endolymphatic hydrops" is characterized by symptoms caused by inner ear disease such as episodic vertigo, tinnitus, and sensorineural hearing loss • can occur at any age but is more common between 30 and 60 years of age pathology: • exact cause is unknown • can be contributed by improper fluid drainage, abnormal immune response, viral infections, and genetic predisposition clinical manifestations: • significant disability due to sudden severe attacks of vertigo • nausea and vomiting • sweating and pallor • hearing loss • tinnitus • aureal fullness • can experience "drop attacks" or feelings of being pulled to the ground diagnostic tests • history and physical examination • audiometric studies (including speech discrimination, tone decay) • vestibular tests (including caloric test, positional test) • neurologic examination • glycerol test - an oral dose of glycerol is given - followed by a series of audiograms over 3 hours - improvement in hearing or speech discrimination = positive test interventions: • drug therapy (sedatives, benzodiazepines, anticholinergics) - used to decrease the abnormal sensation and lessen nausea and vomiting • acute vertigo = bed rest, sedation, and antiemetics or antivertigo drugs (~Antivert) for motion sickness • antihistamine administration • low sodium diet • provide a safe environment • keep a quiet and darkened room • educate patient to avoid sudden position changes • medications and fluids are administered parentally (~input and output) surgery • endolymphatic sac decompression - performed to reduce the pressure on the cochlear hair cells preventing damage • endolymphatic shunt • vestibular nerve section - relief doesn't happen = cutting the vestibular part of the cochleovestibular nerve - eliminates attacks of vertigo • labyrinthectomy - the balance end of organs are removed so that the brain no longer receives signals from the inner ear that sense gravity and motion changes (cochlea is sacrificed)

10. What entails a corneal transplant?

• also known as "keratoplasty" and indications include corneal scarring, keratoconus • inplants include penetrating (~full thickness) and lamellar corneal transplant - penetrating full thickness: transplanting ALL layers of the cornea using a donor - removal of the full thickness of the cornea, replaced with donor, and then sutured into place - vision may not be restored for up to 12 months - lamellar cornea transplant: only SOME layers of the cornea are replaced - more appropriate than full transplants when the disease process is limited to only a portion of the cornea • fastest and safest of all tissue or organ transplant surgeries • time between donor's death and removal of tissue is crucual - donor's are screened for HIV and hepatitis B & C

20. What is external otitis?

• an acute inflammation or infection of the epithelium of the auricle and ear canal pathology: • typically caused by Pseudomonas aeruginosa (~bacterial) • swimming = alter flora of the external ear canal due to chemicals - can result in an infection referred to as "swimmer's ear" clinical manifestations: • pain, discharge, and hearing loss (~if canal swollen shut) • ostaglia is one of the first signs - can experience significant pain with chewing, moving auricle, pressing tragus - may have serosanguineous (~blood-tinged) or purulent (~white to green) fluid misc. types: • malignant external otitis: occurs mainly in older patients with diabetes which can spread from the external ear paraotid gland temporal lobe. - treated with antibiotics diagnostic tests: • made by otoscopic examination as well as cultures to study drainage - care must be taken to avoid pain while pulling the ear nurse management: • moist heat, mild analgesics, and topical anesthetic drops control the pain • anitbiotics (infection) and corticosteroids (inflammation) - improvement should occur in 48 hours - medication therapy lasts 7 to 14 days - hands should be washed prior to ear drop administration - drops should be at room temp. before delivery (can cause vertigo if not) - remain in position for 2 mins aftewards to allow drops to spread

22. What is cerumen impaction?

• ear wax is normal because it lubricates the canal - use earplugs when you are prone to swimmer's ear - turn you head to each side for 30 seconds to help drain water out of ear - do not dry with cotton-tipped applicator - this can cause serious injury to the tympanic membrane and ossicles pathology: • impacted cerumen can cause discomfort and discreased hearing • it is when ear wax is builds up in the ear and blocks the ear canal clinical manifestations: • hearing loss • otalgia • tinnitus • vertigo interventions: • treatment includes irrigation to the canal with body-temperature solutions - solutions are used to soften the cerumen - special syringes are used to irrigate the canal - place the patient in a sitting position with an emesis basis under ear - pull auricle up and back - direct solution flow above or below the impaction • mineral oil or lidocaine drops can be used to kill an insect priro to removal • ears should be cleaned with a washcloth and finger

30. What is presbycusis (aging)?

• hearing loss associated with aging that includes loss of peripheral, auditory, a decline in word recognition ability, and communication issues - cause is related to degenerative changes in the inner ear • occurs gradually and initially affects the ability to hear high-pitched sounds

27. what is benign paroxysmal positional vertigo?

• is a common cause of vertigo (~50% of cases) pathology: • sudden sensation that you're spinning or that inside of your head is spinning • free-floating debris in the semicircular canal causes vertigo with specific head movements such as getting out of bed, rolling over in bed, and sitting from lying - debris or "ear rocks" is composed of small crystals of calcium carbonate - derived from the inner ear - typically due to head trauma, infection, or degeneration of the aging process clinical manifestations: • nystagmus • dizziness • sense that you or your surroundings are spinning and moving • loss of balance • nausea and vomiting diagnostic tests: • history and physical examination interventions: • Epley maneuver (~canalith): effective ni providing symptom relief - the ear debris is moved from areas in the inner ear that causes the symptoms - repositioned into less sensitive areas where they do not cause problems • allow the patient to sit for a movements before getting up • provide safety measures

14. What is age- related macular degeneration?

• is the most common irreversible central vision loss in people over age 60 • it is divided into two categories: - dry AMD: which is the most common that is noticed when close vision starts to become more difficult - macular cells start to atrophy which lead to a slow progression and painless vision loss - starts with the abnormal accumulation of yellowish extracellular deposits which are referred to as drusen - wet AMD: is the most severe form which accounts for most AMD blindness - it has a more rapid onset of vision loss - characterized by the development of abnormal blood vessels near macula - new blood vessels grow and bleed which causes scar tissue to form pathology: • related to retinal aging and a family history (~major risk factor) • chornic inflammation conditions such as smoking and hypertension clinical manifestations: • blurred or darkened vision • scotomas which are blind spots in the visual field • metamorphopsia which is distortion of vision diagnostic tests: • the primary diagnostic procedure = ophthalmoscopy - the examiner looks for the drusen • the amsler test may help define the involved areas and provide baseline measures nurse management: • limited treatment for the wet AMD = medications that are injected directly into the vitreous cavity such as Ranibizumab, Avastin, and Macugen - these medications slow endothelial growth factor help to slow vision loss - injections are given at 4 to 6 week intervals • photodynamic therapy(PDT): uses verteporfin IV and a "cold" laser to excite the dye which is a photosensitizing drug that eliminates abnormal vessels in the eye - caution patients to avoid direct exposure to sunlight for 5 days after treatment because any exposure will activiate the medication

9. What is keratoconus?

• it is a non-inflammatory, typically bilateral disease that has a familial tendency - usually appears during adolescence and progresses slowly before 20 to 60 - the anterior cornea thins and protrudes forward = cone shape - the cone shape deflects light as it enters the eye - only symptom = blurred vision - "intacs inserts" = two clear plastic lenses surgically inserted on the cornea to reduce astigmatism and myopia which is used to delay transplantation

23. What is otitis media?

• it is an infection of the tympanum, ossicles, and space of the middle ear pathology: • swelling of the auditory tube from colds and bacteria trap bacteria which causes a middle ear infection • pressure from inflammation = pushes on the tympanic membrane - causes it to become red, bulging, and painful • typically a childhood disease (~due to the anatomy) • chronic otitis media: recurrance of middle ear infections and sometimes can be resistance to medication therapy - characterized by purulent exudate and inflammation involving the middle ear - it is often painless but may cause hearling loss, nausea, vomiting, and dizziness clinical manifestations: • otaglia • otorrhea • fever • malaise • reduced hearing • referred pain from the temporomandibular joint, teeth, gums, sinuses, or throat diagnostic tests: • history and physical examination • otoscopic examination • culture and sensitivity of middle ear drainage • mastoid x-ray interventions: • ear irrigations • otic, oral, or parenteral antibiotics - high doses of antibiotics is recommended as the first-line therapy • analgesics • antiemetics surgery: • done if there is no response to medication treatments • myringotomy - surgical incision made in the tympanum to release increased pressure and fluid • tympanostomy tube - may be placed for short-term and long-term use - small tube that is inserted into the eardrum in order to keep the middle ear aerated • tympanoplasty - involves the reconstruction of the tympanic membrane and ossicles • mastoidectomy - often performed with a tympanoplasty to remove infected portions of the mastoid

5. What is conjunctivitis and the types?

• it is an infection or inflammation of the conjunctiva which can be caused by a virus, bacteria, exposure to allergens, or STDs. types: 1. bacterial conjunctivtis: also referred to as "pink eye" is a common infection - it occurs in every age group, especially children - S. aureus is the most common cause - complaints are discomfort, pruritis, mucopurulent drainage, tearing - a disharge in one or both eyes that forms a crust during the night that may prevent the eye from opening in the morning - usually is self-limiting and treated with antibiotic drops (~besifloxacin) - teach importance of hand washing and avoiding contact with infected person 2. viral conjunctivitis: caused by many different viruses specifically adenovirus that is highly contagious infection. - most commonly have excessive tearing of the eye, foreign body sensation, redness, and mild photophobia - contracted in contaminated swimming pools and through direct contact with an infected person - treatment is palliative but if severe use of topical corticosteroids 3. chlamydial conjunctivitis: is often a unilateral disease but can involve both eyes - caused by Chlamydia trachomatis - which is a human pathogen that is an intracellular bacterium responsible - it is a major cause of blindness worldwide - transmitted mainly sexually active young adults (~women more commonly) - redness, mucous discharge, crusting of lashes, lid swelling, irritation - antibiotic therapy is usually affective 4. allergic conjunctivitis: is an eye inflammation that is caused by an allergic reaction to substances such as pollen or mold spores - can be mild and transitory or it can be severe - develop intense itching, swelling, tearing, and burning - avoidance of the allergen - artificial tears can be effective in diluting the allergen and washing the eye - effective medications include antihistamines and corticosteroids

6. What is keratitis and the various types?

• it is an inflammation or infection of the cornea that is caused by a variety of microorganisms which may involve the conjunctiva and/or the cornea - if it involves both the cornea and conjunctiva it is called keratoconjunctivitis types 1. bacterial keratitis: infection with a variety of organisms which commonly caused by pseudomonas aeruginosa and staphylococcus aureus - eye pain, redness, blurried vision, photophobia, tearing commonly caused from wearing of contact lenses (not disinfecting contacts properly storing/cleaning lens with water, wearing rigid contact overnight, immunocompromised, recent eye injury - topical antibiotics are typically effective 2. viral keratitis: most frequently occuring infectious cause of corneal blindess that is caused by the herpes simplex virus (HSV) - usually heals without damaging the eye but more severe cases cause scarring - produces watery eyes, photophobia, blurred vision - it spreads by direct contact with someone who is infected with a virus - antiviral treatment includes trifluridine drops (~Viroptic), oral acyclvir (~Zovirax), & topical vidarabine ointment (~Vira-A) - topical corticosteroids are contraindicated because they contribute to a longer course and deeper ulceration of the cornea) 3. acanthamoeba keratitis: it is rare, severe painful infection of the cornea that will usually cause scarring and blindness if it is left untreated - parasite that is associated with a contaminated contact lens wear and care solutions or cases (~homemade saline solution) - commonly produces sensation of something in the eye, excessive tearing, blurred vision, photophobia - caused by storing and handling contact lenses improperly, swimming or using a hot tub, coming into contact with contaminated water - medical treatment is difficult because the organism is resistant to most drugs - antimicrobial therapy or corneal transplant 4. corneal ulceration: it is when tissue is lost which is caused by infection of cornea - it is also referred to as "infectious keratitis" - it is due to bacteria, virus, fungi - resembles a abscess or sore in the eye - very painful, characteristic dendtritic tree-branch appearance, photophobia - aggressive treatment to avoid permenant loss of vision - eye drops as frequently as every hour night and day for the first 24 hours - untreated ulcer = scarring and perforation = corneal transplant

18. What is enucleation?

• it is the removal of the eye due to a blind or painful eye which can result from glaucoma, infection, or trauma • the surgical procedure includes severing the extraocular muscles close to insertion - an implant is inserted to maintain the intraorbital anatomy - suturing of the ends of the extraocular muscles over the implant - pressure dressing helps prevent postoperative bleeding - notify physician if excessive bleeding or swelling, increased pain, displacement of the implant, or temperature elevation - approximately 6 weeks after the wound is healed = permenant prothesis put in

3. What is eye trauma? • the most common ocular injuries is due to home gardening and power tool use

• it refers to any injury to the eye itself • it can be due to mechanial trauma (~blunt or penetrating), chemical agents, or to radiation (~ultraviolet or ionizing) • morgan lens: used to provide continuous irrigation of an injured eye - sterile plastic device = contact lens - floats over the eye and allows copious irrigation of the eye - provides relief of chemical or thermal burns - removes nonembedded foreign materials in the eye

6. What are the internal structures and their functions? • iris provides the color of the eyes which has a small opening (~pupil) that allows light to enter the eye.

• lens is a biconvex, avascular, transparent structure that is located behind the iris - primary function of the lens is to bend light rays so that they focus on retina - accomodation occurs when the eye focuses on a near object and is facilitated by contraction of the ciliary body which changes the shape of the lens. • ciliary body which produces and secretes aqueous humor • choroid is a highly vascular structure that nourishes the ciliary body, iris, and the outer portions of the retina. • retina is the innermost layer of the eye that extends and forms the optic nerve - neurons make up the major portion of the retina (~retina cells can't regenerate) - responsible for converting images into a form that the brain can understand - covered by two types of photoreceptors: a) rods = provide vision in dim or darkened envionrments b) cones = receptive to colors in bright environments • macula is the center of the retina which is responsible for central vision • fovea centralis located at the center of the macula that provides sharp visual acuity

3. What are the refractive errors? • the eyes ability to bend light rays so that they fall on the retina

• parallel light rays are focused through the lens into a sharp image on the retina - when the light does not focus properly = refractive error - myopia: "nearsightedness" can see near objects clearly but objects in the distance are blurred. - hyperopia: "farsightedness" can see distant objects clearly but objects that are close become blurred. - astigmatism: an uneven curvature of the cornea that results in visual distortion - presboyopia: loss of accomodation which causes an inability to focus on near objects which usually appears around age 40.

19. What does trauma to the ear involve?

• trauma to the external ear can cause injury to the subsuctaneous tissue that can result in a hematoma - not aspirated it can lead to inflammation of the membranes (~perichondritis) • head trauma that injures the temporal lobe of the cerebral cortex can impair the ability to understand meaning of sounds