Sensory System Function, Assessment, and Therapeutic Measures PDF

4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1212 51 Sensory System Function, Assessment, and Therapeutic Measures:...

4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1212 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing KEY TERMS LAZETTE V. NOWICKI accommodation (ah-KOM-uh-DAY-shun) AND JANICE L. BRADFORD arcus senilus (AR-kuss seh-NILL-uss) cochlear implant (KOK-lee-ur IM-plant) consensual response (kon-SEN-shoo-uhl ree-SPONS) LEARNING OUTCOMES electroretinography (ee-LEK-troh-RET-in-AW-gruh-fee) esotropia (ESS-oh-TROH-pee-ah) 1. Describe the normal anatomy of the sensory system. exotropia (EKS-oh-TROH-pee-ah) 2. Explain the normal function of the sensory system. hearing aid (HEER-ing AYD) hypotropia (HYE-poh-TROH-pee-ah) 3. List data to collect when caring for a patient with a disorder nystagmus (nye-STAG-mus) of the sensory system. ophthalmologist (AWF-thal-MAW-luh-jist) 4. Identify diagnostic tests commonly performed to diagnose ophthalmoscope (awf-THAL-muh-skohp) optician (awp-TISH-uhn) disorders of the sensory system. optometrist (awp-TOM-uh-trist) 5. Plan nursing care for patients undergoing diagnostic tests otalgia (oh-TAL-jee-ah) for sensory disorders. otorrhea (OH-toh-REE-ah) ototoxic (OH-toh-TOK-sik) 6. Describe therapeutic measures for patients with disorders ptosis (TOH-sis) of the sensory system. Rinne test (RIH-nee TEST) Romberg’s test (RAHM-bergs TEST) Snellen’s chart (SNEL-enz CHART) tropia (TROH-pee-ah) Weber test (VAY-ber TEST) 1212 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1213 Chapter 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing 1213 Our eyes and ears pro vide us with a great deal of sensory information. It is difficult to imagine what it would be like not VISION to see or hear the w orld around us. Nurses ha ve an important role in assessing vision and hearing. Patients depend on health Normal Anatomy and Physiology of the Eye care personnel to assist them in maintaining these primary External Structures senses. To learn more about ways to promote vision and hearing Several structures protect the eye from debris and desiccation health, visit http://web.health.gov/healthypeople. (extreme dryness; Figs. 51.1 and 51.2). Eyebrow: Perhaps the most significant role of the eyebrows is to Eyelashes: These hairs along the edges of the enhance facial expressions, aiding in nonverbal communication. They eyelids help keep debris out of the eye. Touching also help keep perspiration out of the eye and shield the eye from glare. the eyelashes stimulates the blink reflex. Eyelids (palpebrae): Conjunctiva: The Formed primarily by the conjunctiva is a transparent orbicularis oculi muscle mucous membrane that lines covered with skin, the eyelids the inner surface of the protect the eye from foreign eyelid and covers the bodies and block light when anterior surface of the closed to allow for sleeping. eyeball (except for the Periodic blinking also helps cornea). It secretes a thin moisten the eyes with tears mucous film to help keep the and wash out debris. eyeball moist. It is very vascular, which becomes apparent when eyes are Lateral canthus “bloodshot,” a result of dilated vessels in the conjunctiva. Medial canthus Palpebral fissure: This is the opening between the lids. Tarsal glands: These glands, which lie along the thickened area at the edge of the eye (called the tarsal plate), secrete oil to slow the evaporation of tears and help form a barrier seal when the eyes are closed. FIGURE 51.1 Accessory structures of the eye. From Thompson, G. S. (2013). Understanding anatomy and physiology. Philadelphia: F.A. Davis, p. 209. Lacrimal gland: This small gland secretes tears that flow onto the surface of the conjunctiva. Tears clean and moisten the eye’s surface and Ducts also deliver oxygen and nutrients to the conjunctiva. Furthermore, Lacrimal tears contain a bacterial enzyme sac called lysozyme that helps prevent infection. Lacrimal punctum: This is a tiny pore through which tears Lacrimal drain into the lacrimal canal canal and the nasolacrimal duct. Nasolacrimal duct: This passageway carries tears into FIGURE 51.2 Lacrimal apparatus. the nasal cavity (which explains From Thompson, G. S. (2013). why crying or watery eyes can Understanding anatomy and cause a runny nose). physiology. Philadelphia: F.A. Davis, p. 209. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1214 1214 UNIT FOURTEEN Understanding the Sensory System Structure of the Eyeball is, therefore, the area of most acute color vision. Rods are proportionately more abundant toward the periphery of the Most of the e yeball is within the orbit, the bon y socket that retina, and for this reason night vision is best at the sides of protects the eye from trauma. The six extrinsic muscles that the visual field. move the e yeball are attached to the orbit and to the outer Neurons called ganglion cells transmit the impulses surface of the eyeball. There are four rectus muscles that move generated by the rods and cones. These neurons all converge the eyeball side to side or up and do wn, and tw o oblique at the optic disc and pass through the w all of the eyeball as muscles that rotate the e ye. The cranial nerves that innervate the optic nerve. The optic disc may also be called the blind these muscles are the oculomotor , trochlear, and abducens spot because no rods or cones are present. (third, fourth, and sixth cranial nerv es, respectively). Actions of the six extrinsic eye muscles not only allow voluntary control of movement but also will be innerv ated by the autonomic Physiology of Vision nervous system to perform con vergence, an alignment of the Vision involves the focusing of light rays on the retina and visual axis of each eye on the same field of view. the transmission of the subsequent nerv e impulses to the The wall of the eyeball has three layers: the outer f ibrous visual areas of the cerebral cortex. tunic (sclera and cornea), the middle v ascular tunic (choroid, The refractive structures of the e ye are, in order , the ciliary body that suspends the lens, and iris), and the inner cornea, aqueous humor, lens, and vitreous humor. The lens nervous tunic (retina; Fig. 51.3). The lens divides the interior is the only adjustable part of this focusing system. When the of the eye into two main cavities: anterior cavity and posterior eye shifts focus to an object that is near , accommodation of cavity (Fig. 51.4). Anterior to the lens is the ring-shaped curtain the lens occurs (Fig. 51.5). Also, the pupil will constrict in called the iris, which di vides the anterior ca vity into tw o near vision to force photons through the thickness of the lens chambers: anterior chamber and posterior chamber. (Fig. 51.6). Accommodation and pupil constriction increase The retina lines the posterior two-thirds of the eyeball and the number of photons that strike the fovea centralis. contains the photoreceptors (rods and cones). Rods detect When photons strike the retina, the y stimulate chemical only the presence of light, whereas cones respond to photons reactions in the rods and cones. Resultant changes generate of differing wavelengths. The fovea centralis is a small a nerve impulse for transmission. Rods generate an action depression in the macula lutea of the posterior retina, directly potential in dim light b ut only allow shades of gray vision. behind the center of the lens, and contains only cones. It The cones are specialized to respond to a portion of the visible Fibrous Outer Layer Neural Inner Layer The sclera—formed from dense connective tissue— is the The retina is a thin layer of light-sensitive cells. outermost layer of the eye. Most of the sclera is white and opaque; it forms what is called “the white of the eye.” Blood vessels and nerves run throughout the sclera. Exiting from the posterior portion of the eyeball is the optic nerve (cranial nerve The cornea is a transparent extension II), which transmits signals of the sclera in the anterior part of the to the brain. eye. It sits over the iris (the colored portion of the eye) and admits light into the eye. It contains no blood vessels. Vascular Middle Layer The iris is a ring of colored muscle; it works to adjust the diameter of the pupil (the central opening of the iris) to control the amount of light entering the eye. The ciliary body is a thickened extension of the choroid that forms a collar around the lens. It also secretes a fluid called aqueous humor. The choroid is a highly vascular layer of tissue that supplies oxygen and nutrients to the retina and sclera. FIGURE 51.3 Eye tissue layers—fibrous, vascular and neural. From Thompson, G. S. (2013). Understanding anatomy and physiology. Philadelphia: F.A. Davis, p. 211. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1215 Chapter 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing 1215 The space between the lens and the cornea is the anterior cavity. This cavity is further divided into an anterior chamber (anterior to the iris) and a posterior chamber (posterior to the iris but anterior to the lens). A clear, watery fluid called aqueous humor fills the anterior cavity. Anterior chamber Canal of Schlemm The lens is a Posterior chamber transparent disc of tissue just behind the pupil, between the anterior and posterior cavities. The lens changes shape for near and far vision. The posterior cavity is the larger cavity lying The ciliary body secretes aqueous humor that fills the posterior to the lens. It is filled with a jelly-like anterior cavity. The fluid flows from the posterior chamber, substance called vitreous humor. This semi-solid through the pupil, and into the anterior chamber. It then material helps keep the eyeball from collapsing. drains into a blood vessel called the canal of schlemm. FIGURE 51.4 Chambers and fluids. From Thompson, G. S. (2013). Understanding anatomy and physiology. Philadelphia: F.A. Davis, p. 212. Lens thins Lens thickens Ciliary muscle Ciliary muscle contracted relaxed The nearly parallel light rays from distant objects require The more divergent light rays from a nearby object require little refraction. Consequently, the ciliary muscle encircling more refraction. To help focus the light rays, the ciliary the lens relaxes and the lens flattens and thins. muscle surrounding the lens contracts. This narrows the lens, causing it to bulge into a convex shape and thicken, giving it more focusing power. FIGURE 51.5 Accommodation of the lens. From Thompson, G. S. (2013). Understanding anatomy and physiology. Philadelphia: F.A. Davis, p. 215. light spectrum; there are red-absorbing, blue-absorbing, and righted and the slightly different pictures from the two eyes green-absorbing cones. Differing combinations of three cone are integrated into one image; this is binocular vision, which types allow interpretation of color (Fig. 51.7). also provides depth perception. Refraction inverts the image onto the photoreceptors in the retina. The impulses from the rods and cones are Aging and the Eye transmitted to the ganglion neurons, which con verge at the The most common changes in the aging eye are those in the optic disc and become the optic nerve. The optic nerves from lens (Fig. 51.8). With age, the lens may become partially or both eyes converge at the optic chiasma, just in front of the totally opaque. The lens also loses its elasticity with age; most pituitary gland. Here, the medial f ibers of each optic nerv e people become farsighted as they age and by 40 years begin cross to the other side. This crossing permits each visual area to need corrective lenses. Peripheral vision losses may occur. to receive impulses from both e yes, which is important for Depth perception decreases and glare intensif ies, both of binocular vision. which can affect safety. Color vision f ades with lesser dis- The visual areas are in the occipital lobes of the cerebral crimination of blue, green, and violet colors. Red, yellow, and cortex. It is here that the upside-do wn retinal images are orange colors are best visible. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1216 1216 UNIT FOURTEEN Understanding the Sensory System The pupillary constrictor muscle encircles the pupil. When stimulated by the parasympathetic nervous system, the Pupil muscle constricts, narrowing the pupil to admit less light. Pupillary constrictor muscles Pupillary dilator The pupillary muscles dilator looks like the spokes of a wheel. When stimulated by the sympathetic nervous system, this muscle contracts, pulling the inside edge of the iris outward. This FIGURE 51.6 Constriction of the pupil. widens the pupil and From Thompson, G. S. (2013). admits more light. Understanding anatomy and physiology. Philadelphia: F.A. Davis, p. 215. Rods Cones Are located at the Are concentrated periphery of the retina in the center of Are active in dim light the retina (but are Are responsible for also scattered night vision throughout the Cannot distinguish retina) colors from each other Are active in bright light Are primarily responsible for sharp vision Are responsible for color vision Nucleus Nucleus FIGURE 51.7 Action of photoreceptors. From Thompson, G. S. (2013). Understanding anatomy and physiology. Philadelphia: F.A. Davis, p. 216. Nursing Assessment of the Eye and Visual alerts the nurse to potential alterations in e ye health. Patients Status are asked about their general health and diseases such as diabetes and hypertension. A patient medication review looks Nursing assessment of the e ye begins with the collection for any ocular (eye) effects. Then, the nurse asks the patient of subjective data, then mo ves to observation and testing, about any changes in visual acuity or symptoms of abnormality and finally, a more invasive physical examination. Licensed (Table 51.1). practical nurses/licensed v ocational nurses (LPN/L VNs) usually assist the health care pro vider (HCP) in conducting Physical Examination invasive data collection. VISUAL ACUITY. Objective data collection begins by checking Health History the patient’s visual acuity (Table 51.2). Visual acuity is meas- The nurse asks about f amily history that may af fect vision, ured in a v ariety of ways but usually starts with the use of particularly glaucoma, diabetes, blindness, and cataracts. Many Snellen’s chart, an E chart, or a handheld visual acuity chart eye disorders are genetically transmitted, so this information (Rosenbaum’s card) to test near and far vision. Snellen’s chart 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1217 Chapter 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing 1217 visual acuity chart is used to indicate visual acuity by having The Aging the patient hold the card approximately 14 inches from the Sensory eyes. The test is conducted and documented in the same way System Color as the Snellen’s and E chart examinations. vision fades Visual Fields by Confrontation. The examiner also tests peripheral vision, which is the ability of the eye to see objects Glare peripherally while the e ye is fixed or kept in one position. adaption This is also known as testing visual fields by confrontation. difficult Eyes Ears To do this, the e xaminer compares his or her o wn ability to see peripheral objects with that of the patient.This test should Peripheral be done with an examiner who has normal peripheral vision. vision Difficult The examiner stands 2 feet in front of, and facing, the patient decreases to filter background and instructs the patient to co ver one e ye. The examiner noises covers his or her o wn corresponding e ye (the e ye that is Depth Lens aligned with the patient’s eye; e.g., if the patient’s right eye perception Organ of is covered, the examiner’s left eye is covered). The examiner decreases Corti hair cell damage uses the arm opposite the covered eye, extends it to the space midway between the patient and the examiner, and brings it Impaired Opacity verbal toward the eye from three directions: superior , inferior, and Farsightedness commun- temporal (middle). The examiner wiggles the finger while ication moving the arm. The examiner asks the patient to look Decreased High straight ahead and indicate at what point he or she is able to elasticity pitch see the examiner’s finger. One eye is tested and then the other. range Reading loss The patient has full visual f ields if the point at which the glasses patient sees the finger matches that at which the e xaminer needed F, S, K, Sh sees it. The examiner documents the results as “visual fields Decreased sounds lost equal to e xaminer,” “full visual f ields,” or, if abnormal, vision first “visual fields unequal to examiner in...” (identify position, e.g., left superior). FIGURE 51.8 Aging and the sensory system. MUSCLE BALANCE AND EYE MOVEMENT. The examiner tests extraocular muscle balance and cranial nerv e function by has alphabetical letters graduating in size from the smallest on instructing the patient to look straight ahead and follo w the the bottom to the largest on the top (Fig. 51.9). The examiner examiner’s finger movement without moving his or her head. measures 20 feet and marks the distance on the floor. The As with the confrontation test, the patient and examiner face examiner then asks the patient to co ver one eye with a 3 × 5 each other either standing or sitting. The examiner moves his card or eye cover and then read out loud an indicated line of or her finger in the six cardinal f ields of gaze, coming back letters. The lowest line on the chart that the patient is able to to the point of origin between each field of gaze (Fig. 51.10). read accurately is used to indicate visual acuity for that e ye. If the patient’s eyes are able to follow the examiner’s finger Normal vision is 20/20, which means the patient can read at in all fields of gaze without nystagmus, the patient is assessed 20 feet what the normal eye can read at 20 feet. to have adequate extraocular muscle strength and innervation. Low vision occurs at 20/70 and le gal blindness at 20/200 Nystagmus is an involuntary, cyclical, rapid movement of the or less in the best e ye with the best possible correction. An eyes in response to vertical, horizontal, or rotary movement. example of visual findings is the patient who identif ies all of The corneal light reflex test assesses muscle balance. This the letters correctly on the line mark ed 30; this patient has a test is conducted by shining a penlight toward the cornea while visual acuity of 20/30. This means that the patient can see at the patient is staring at an object straight ahead. The light 20 feet what the a verage individual can see at 30 feet. The reflection should be at exactly the same place on both pupils. examination is conducted on both e yes separately, then If the eyes lack symmetry, muscle weakness could be present. together, and documented as follo ws: “oculus dexter (OD) The cover test is used in conjunction with an abnormal [right eye] 20/30, oculus sinister (OS) [left eye] 20/20, oculus corneal light refle x test to e valuate muscle balance. The uterque (OU) [both eyes] 20/20.” patient is asked to look straight ahead at a f ar object. The In addition to identifying the e ye tested, the e xaminer examiner covers one of the patient’s eyes with a 3 × 5 card. conducts the e xamination with and without the patient’ s The uncovered eye should have a steady gaze; if it mo ves, corrective lenses, if applicable. When corrective lenses are there may be muscle weakness. Ne xt, the cover is quickly used, documentation reflects this as “OD 20/100 without removed and the action of this e ye is observed. If this e ye correction, OD 20/20 with correction. ” The E chart is used moves to fixate on the light instead of staring straight ahead, for patients who have literacy issues. The patient is asked to it indicates a drifting of the eye when it was covered, which is indicate the direction of the E-shaped f igure. The handheld a sign of muscle weakness. This deviation of the eye away 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1218 1218 UNIT FOURTEEN Understanding the Sensory System TABLE 51.1 SUBJECTIVE DATA COLLECTION FOR THE EYE Category Questions to Ask During the Health History Rationale/Significance Family Do you have any family members with a history of diabetes? Many eye disorders are History Hypertension? Cataracts? Glaucoma? Blindness? Diabetes genetically transmitted. mellitus? Do any family members wear glasses or contact lenses? Is their vision corrected with the lens? Patient’s How would you describe your general health? Some metabolic disorders are General What health problems do you currently have? How are they precursors to eye disorders, Health treated? such as diabetes and What health problems have you had in the past? hypertension. Have you ever had trauma to your eyes? Assess for ocular effects of What medications do you take? systemic medications. How often do you have eye examinations? Assess preventive practices. When was the last time you had an eye examination? Visual Do you wear glasses or contact lenses? Any of these signs and Acuity Have you had any changes in vision such as difficulty seeing symptoms could indicate distances, difficulty seeing close up, difficulty seeing at night? visual disorders/disturbances. Do you see things double? Do you have clouded vision? Do you see halos around lights? Does it look like you are looking through a veil or web? Is there sensitivity to light? Is there pain? Itching? Tearing? Burning? Do you have headaches? If so, what are the precipitating events? TABLE 51.2 OBJECTIVE DATA COLLECTION FOR THE EYE Category Physical Examination Findings Possible Abnormal Findings/Causes Visual Acuity Normal vision is 20/20. Hyperopia, myopia, presbyopia, blurred or cloudy vision Possible causes: refractive error, opacity, or disorder of pathway Visual Fields Full peripheral fields Peripheral field loss Muscle Balance Movement in all six cardinal fields Nystagmus and Eye of gaze Inability to move in all six fields can indicate cranial Movement Corneal light reflex test (Light is at nerve impairment the same place on both pupils.) Asymmetry could mean muscle weakness Cover test–steady gaze Drifting eye indicates muscle weakness Pupillary Reflexes Pupillary light reflex Dilated, fixed, or constricted pupils Accommodation Absence of constriction or convergence External Structures Inspection and palpation of Ptosis (drooping of eyelid) usually indicates nerve eyebrows, orbital area, eyelids, dysfunction. palpebral fissure, medial canthus, Opaque whitening of outer rim of cornea can indicate irises, corneal clarity, anterior arcus senilus. chamber Corneal opaqueness can be from cataract or trauma. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1219 Chapter 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing 1219 The patient is told to focus on an object far away. The size and shape of the pupils are observ ed. The examiner continues to observe the pupils as the patient focuses on a near object (the examiner’s penlight or finger) held approximately 5 inches from the patient’ s face. Normally, the patient’ s eyes turn inward and the pupils constrict. These responses, convergence and constriction, are called accommodation (“Gerontological Issues—Age-Related Changes in Vision and Hearing”). Examiners use the acronym PERRLA to indicate pupils equal, round, reactive to light, accommodation. If accommodation is not tested along with the other tests, the examiner may use the acronym PERRL. WORD BUILDING esotropia: eso—inward + tropia—movement of the eye exotropia: exo—out + tropia—movement of the eye FIGURE 51.9 Using Snellen’s chart to assess visual acuity. Gerontological Issues Age-Related Changes in Vision and Hearing CN III CN III Vision Older adults commonly ha ve the following changes in their vision: Presbyopia, an inability to focus up close because of decreased elasticity in the ocular lens CN VI CN III Narrowing of the visual field and more difficulty with peripheral vision Decreased pupil size and responsiveness to light Difficulty with vision in dimly lit areas or at night (requires more light to see adequately) Increased opacity of the lens, which causes sensitivity CN III CN IV to glare, blurred vision, and interference with night FIGURE 51.10 Six cardinal fields of gaze. vision Yellowing of the lens, which reduces ability to differen- from the visual axis is known as tropia. Deviation of the eye tiate low-tone colors of blues, greens, and violets toward the nose is known as esotropia, movement laterally is (yellow, orange, and red hues are more clearly visible) known as exotropia, and downward deviation is hypotropia. Distorted depth perception and difficulty correctly judging the height of curbs and steps PUPILLARY REFLEXES. When observed, the pupils should be Decreased lacrimal secretions round, symmetrical, and reactive to light. To test pupillary Because visual accommodation decreases with aging, response to light, both consensual and direct e xaminations older adults have an increased risk of f alling. An older should be completed. A slightly darkened room works best. person has difficulty making a visual adjustment when The patient is asked to look straight ahead, and the size of the moving from a well-lit room into the evening darkness, pupil is noted. A penlight is shone to ward the pupil from a for example, or when stepping out of a dark area into the lateral position, and the movement of the pupil is observ ed. sunlight. The pupil should quickly constrict. The size of the pupil is The increased time needed to accommodate to near noted when it constricts. This is known as direct response. and far, dark and light, is often the reason that older To conduct a consensual pupil e xamination, observe the adults do not drive at night. Usually the y say that light eye just tested for reaction while shining the penlight into the from oncoming traffic blinds them or that their e yes do other eye. The observed pupil should constrict. This is known not focus properly. as consensual response. Then repeat the procedure for the One of the simplest and most ef fective ways to im- opposite eye. prove vision for older adults is to ensure that e yeglasses The examiner proceeds to test for accommodation, which are clean. is the ability of the pupil to respond to near and far distances. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1220 1220 UNIT FOURTEEN Understanding the Sensory System Hearing assist the practitioner in the e xamination. To perform the internal eye examination, specialized equipment must be Presbycusis is an age-related change in which progressive used. It is useful, but not always necessary, to have the pupil hearing loss is caused by loss of hair cells and decreased dilated for the internal e ye examination. Having a dark blood supplying the ear, resulting in a decreased ability to room allows the pupil to dilate, as does the application of hear high-frequency sounds. Deafness or decreased hearing anticholinergic mydriatic (causing dilatation) eyedrops. acuity is one of the main reasons that older adults withdraw The handheld instrument with a light source used to examine from social activities. The loss of h igh-pitched hearing the internal eye is called an ophthalmoscope. The ophthalmo- causes the older adult to hear distracting background scope magnifies the internal structures of the e ye, so the noises more clearly than conversation. examiner can visualize the retina, optic nerv e, blood vessels, Older adults who are deaf may need adapti ve equip- and macula. The patient is asked to hold the head still with the ment in their home for safety. The use of a hearing aid eyes focused on a distant object and informed that the bright can increase hearing for those who do not ha ve nerve light might be uncomfortable. The ophthalmologist can also damage deafness. The use of flashing lights instead of examine the internal e ye using a stationary de vice called a buzzers or alarms increases the safety of an older adult slit-lamp microscope. For this, the patient is seated and rests who is not able to hear a smoke detector or fire alarm. the chin on a support while a microscope and light source are directed into the eye. Intraocular Pressure. Estimation of intraocular pressure is measured by using one of several types of tonometer. Often, INSPECTION AND PALPATION OF EXTERNAL STRUCTURES. the procedure is performed with anesthetic drops being The extraocular structures are inspected be ginning with the instilled. One type of tonometer testing uses a puf f of air to eyebrows. The presence of eyebrows, symmetry, hair texture, make an indentation in the cornea to measure intraocular size, and e xtension of the bro w are noted. The examiner pressure. Readings abo ve the normal range may indicate inspects and palpates the orbital area for edema, lesions, glaucoma. puffiness, and tenderness. Then the eyelids are inspected for symmetry, presence of eyelashes, eyelash position, tremors, Diagnostic Tests for the Eye flakiness, redness, and swelling. The patient is asked to open There are a number of diagnostic tests for the e ye, including and close the eyelids. When open, the eyelid should cover the bacterial culture, digital imaging, optical coherence tomography, iris margin but not the pupil. The distance between the upper fluorescein or indocyanine green angiography, electroretinogra- and lower eyelid, known as the palpebral fissure, is inspected; phy, ultrasonography, and other imaging tests. it should be equal in both e yes. If the palpebral f issure is nonsymmetrical, observe for ptosis, a drooping of the eyelid, Eye Culture which is commonly seen in stroke patients. Next the medial If exudate from any portion of the eye or surrounding structure canthus of the lower lid is gently palpated and observ ed for is present, an e ye culture may be ordered. Results of the exudate. The eyelids are palpated for nodules while the e ye culture determine if anti-infective treatment is necessary. is palpated for firmness over the closed eyelid. The lower eyelid is pulled down, and the patient is asked to Digital Imaging look upward. The conjunctiva and sclera are inspected for Digital imaging is a newer way of viewing the retina without color, discharge, and pterygium (thickening of the conjunctiva). requiring the use of dilating eyedrops. The instrument takes a To inspect the upper e yelid, the upper lid is e verted (turned digital picture of the retina in 2 seconds. The majority of the inside out) over a cotton-tipped applicator. The patient blinks retina is viewable and assists in early detection of eye disease. to return the eyelid to its resting position when the inspection It provides a permanent photographic reference for the retina. is complete. The external eyes are inspected for color and symmetry of Optical Coherence Tomography (OCT) the irises, clarity of the cornea, and depth and clarity of the OCT takes a picture of the retina. It is safe, f ast, and does anterior chamber. Shining a light obliquely across the cornea not have the risks associated with the use of dye. Light beams assesses the clearness of the cornea. The cornea should be are shone into the e ye at various angles and the amount of transparent without cloudiness. In individuals older than 40 interference is measured creating a detailed image of the years, there may be bilateral opaque whitening of the outer depth of the retina. rim of the cornea known as arcus senilus. It is caused from lipid deposits and is considered normal. It does not af fect Fluorescein or Indocyanine Green Angiography vision. The anterior chamber (the area between the cornea Angiography with dye is a test using special cameras to find and the iris) of the e ye is inspected using oblique light. The leaking or damaged blood v essels in the retinal or deeper anterior chamber should be clear when the light shines on it. choroidal circulation. Fluorescein is a yellow dye that glows INTERNAL EYE EXAMINATION. Examination of the internal in visible light and is useful for sho wing the retinal circula- eye is done by the advanced practitioner. The LPN/LVN may tion, and indocyanine green is a green dye that shows up with be required to e xplain the procedure to the patient and to invisible infrared light to highlight the choroidal circulation. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1221 Chapter 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing 1221 The patient is assessed for dye aller gies (indocyanine green Eye Hygiene contains iodine) before the procedure. Then the pupil is It is important to k eep debris out of the e yes to pre vent dilated and the dye is injected into the patient’ s venous scratching of the e ye’s delicate surf aces. When a foreign system where it tra vels to the e ye’s circulation to mak e the object gets into the eye, such as dirt or an eyelash, the person blood vessels there visible. Fluorescein is used in diabetic should be taught not to rub the eye but to allow tears to wash retinopathy and retinal vascular disease. Indocyanine green out the object. This can be done by pulling the e yelid down is useful for the wet form of macular de generation when over the eye for a brief time. When wiping the eyes, the nurse blood is present in the macula. should wipe from the inner canthus to the outer canthus. Electroretinography Nutrition for Eye Health Electroretinography is useful in diagnosing diseases of the Adequate nutrition is important for e ye health (“Nutrition rods and cones of the eye. The procedure evaluates differences Notes”). Eye disorders related to inadequate vitamin intak e in the electrical potential between the cornea and retina in re- include corneal damage and night blindness from lack of sponse to light wavelengths and intensity. The test is conducted vitamin A and optic neuritis as a result of vitamin B deficiency. by placing contact lenses with electrodes directly on the eye. Eye Safety and Prevention of Injury Ultrasonography Many people in the United States suffer eye injuries each year. Ultrasound is useful when the internal eye cannot be visualized Common household activities are responsible for the majority directly because of obstructions such as corneal opacities or of injuries. Activities such as microwave cooking, lawn care, bloody vitreous. The eye is anesthetized with instillation of and shooting rubber bands and BB guns all contrib ute to eye anesthetic drops, and a transducer probe is placed on the e ye injury. Many of these injuries could be prevented with education to perform the ultrasound. and implementation of safety measures (Table 51.3). Imaging Tests Eye Irrigation X-ray films show bone structure and tumors. Computed If it is necessary to irrigate foreign bodies or chemical substances tomography (CT) and magnetic resonance imaging (MRI) out of the eye, the nurse prepares the patient by e xplaining the visualize ocular structures and abnormalities of the e ye and surrounding tissues. Therapeutic Measures for the Eye and Vision Nurses have an important role in screening and educating Nutrition Notes individuals, families, and the community about the care for healthy eyes and prevention of disease. To learn more about Nutrition and Eye Disease ways to promote vision health, visit www.lighthouse.org. In some developing countries, vitamin A deficiency is a For resources to help those persons who are blind, visit the leading cause of pre ventable blindness and the leading American Foundation for the Blind at www.afb.org or the cause of childhood blindness. In de veloped countries, National Federation of the Blind at www.nfb.org. antioxidants have been investigated in relation to cataracts and age-related macular de generation (AMD), tw o Regular Eye Examinations conditions that can also lead to severely impaired vision. People who are not kno wn to have visual deficits and do not Little evidence supports a role for antioxidants in prevent- have diseases associated with visual loss, such as diabetes, ing cataracts, and further research ef forts along that line should have their eyes examined at regular intervals throughout are discouraged. Research on AMD is ongoing. Evidence their life. Screening tests usually are done during an annual suggests that antioxidant vitamin and mineral supplemen- physical examination to detect gross visual def icits. Patients tation may delay the progression of AMD in people who wear corrective lenses or have disease processes that place already diagnosed with the disease. Other risk factors for them at risk for visual loss should have their eyes examined by AMD are modifiable obesity-related risk factors, notably an eye care provider at least yearly. low physical activity and serum lipid levels. Eye care pro viders include the ophthalmologist and optometrist. An ophthalmologist is a physician who specializes Recommendations in the comprehensi ve care of the e yes and visual system, The value of specific foods or nutrients in preventing eye including diagnosing and treating eye diseases. An optometrist disease has not been proven. If a person chooses to take specializes in e ye examinations to identify visual defects, supplements, a multivitamin and multimineral product diagnosis problems, prescribe correcti ve lenses or other at recommended dietary allowance levels is advocated treatments, and refer for medical treatment. The optometrist is rather than separate preparations of individual nutrients. not a physician but is identified as a doctor of optometry. An Other choices should be made in consultation with the optician is a person trained to grind and fit lenses according to patient’s HCP. prescriptions written by the ophthalmologist or optometrist. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1222 1222 UNIT FOURTEEN Understanding the Sensory System TABLE 51.3 EYE SAFETY AND INJURY PREVENTION To Protect From Use These Eye Safety Measures Foreign objects Wear safety goggles. Avoid mowing over rocks or sticks. Always wear safety goggles when using lawn edging yard devices. Chemical splashes Use splash shields when working with chemicals such as cleaning solution or body fluids. Close eyes to avoid getting hair spray in them. Corneal lens abrasions/infections Follow manufacturer’s or eye care professional’s directions for length of use from contact lenses and cleaning procedures. Do not overwear lenses. Ultraviolet light (UV) Wear ultraviolet-protected sunglasses when outdoors. Instruct patients to wear sunglasses with side shields after administration of mydriatics. Wear a hat to shield sun. Visual deficits in adult with Update prescription of glasses yearly. corrective lenses Glasses should fit properly, be clean, and be free of scratches. Eye strain from computer usage The position of the bottom of the monitor should be 20 degrees below the line of sight and should be positioned 13 to 18 inches from the eyes. The light in the room should prevent glare. Increase the font size on the screen if letters appear too small. If dry eyes are a problem while using a computer, adjust the monitor to a lower level so the eyes do not have to open as wide, which increases evaporation. Eye injury from sports Wear protective eyewear with polycarbonate lenses. Wear facemasks or helmets while participating in any high-contact or high- impact sports. procedure. An isotonic solution is usually used. It is deli vered Chapter 52 discusses specif ic ophthalmic medications onto the eye using intravenous (IV) tubing or a Mor gan lens and their uses. To identify the steps in the application of (Box 51-1 and Fig. 51.11). eye medications, see Box es 51-2 and 51-3. Whenever eye medications, especially eyedrops, are administered, the punc- Guide Dogs for the Blind and Visually Impaired tum (tear duct) of the e ye should have pressure applied to it Special guide dogs are trained to lead blind and visually by either the nurse wearing glo ves or the patient, if able, for impaired people around obstacles. Generally they are allowed at least 1 minute or longer as directed. This reduces systemic in places where animals are banned such as stores or restaurants. absorption of the medication through the punctum. Some eye While the dogs are w orking, they should not be approached, medications can have serious cardiac or respiratory ef fects, touched, or fed without their owner’s permission. and patients have had life-threatening reactions to them. The nurse should teach the patient the proper instillation of e ye Medication Administration medications to reduce these reactions. A variety of drugs are available for eye application. Most are applied as drops, ointments, or irrigations. The nurse must know the usual dosage and strength, desired action, side effects, and contraindications of the medication being admin- NURSING CARE TIP istered to pre vent harm to the patient. Systemic adv erse Older patients, when instilling their own eyedrops, reactions can occur, and diseases can be exacerbated from the may not feel the drops go in. Teaching patients administration of eye medications. Older adults are especially to refrigerate the drops, if not contraindicated, susceptible to this because they have more chronic diseases, for 15 to 30 minutes before instillation helps as well as use ophthalmic agents long term.These agents can them feel if the drops go into the eye or on interact with other medications the patient is taking. So the the face. nurse observes patients for possible reactions. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1223 Chapter 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing 1223 Box 51-1 Eye Irrigation Box 51-2 Administration of 1. Explain procedure to patient. Eyedrops 2. Perform hand hygiene. 1. Explain procedure to patient. Contact lenses should 3. Gather equipment. For low-volume irrigation, a be removed. They should not be worn if eyes are prefilled squeezable bottle is used. For large-volume reddened, and for 10 minutes after drops have been irrigation, an IV bag of isotonic solution such as instilled or as directed. normal saline or lactated Ringer’s solution is used. Attach IV tubing to the bag and flush the line. 2. Assess allergies, and check medication dosage, 4. Apply anesthetic drops, if ordered. strength, side effects, contraindications, and 5. Place a basin by side of patient’s head and pad area expiration date. Do not use if solution is cloudy. with towels to absorb irrigant. 3. Perform hand hygiene and apply gloves. 6. Apply gloves. 4. Avoid touching tip of dropper to anything to avoid 7. Eye may be irrigated by holding distal end of IV contamination that could cause an eye infection. tubing at inner canthus of the eye, or a Morgan lens Do not wash or rinse dropper. may be attached (see Fig. 51.11). Lens is placed 5. Instruct patient to tilt head backward and look up directly on the anesthetized eye, and tubing is toward the ceiling. connected to IV bag tubing. Proceed with irrigation 6. Gently pull lower lid down and out to form a using a slow, steady stream of irrigant. Generally, use pocket to catch eyedrop. of the Morgan lens is more comfortable for patients 7. Approach patient’s eye from the side and instill because eyelids do not need to be held open. prescribed amount of medication into the pocket. 8. Assess patient’s tolerance to the procedure. It is helpful (including for patient who is self- 9. Remove Morgan lens if used. administering eyedrops) to use the forehead as a 10. Remove gloves. Perform hand hygiene. stabilizing area for the hand administering the drop. 11. Document assessment, type and amount of irrigant, 8. Release lower eyelid. Have patient close eye. and patient’s tolerance of procedure. 9. Apply gentle pressure with a tissue to the punctum (over the tear duct) for at least 1 to 5 minutes to keep medication from being systemically absorbed. Nurse or patient can do this. EYE PATCHING. After treating an injured or infected eye, the 10. Wipe excess medication off eyelids or cheek. physician may order the eye to be patched. The nurse applies 11. If another eyedrop is to be given, wait 5 to ointment or drops if ordered, asks the patient to keep the eyelid 10 minutes before administering. shut, and then places a disposable, cotton gauze eye patch over 12. Remove gloves. Perform hand hygiene. the depression of the eye socket. If the patient has a deep eye 13. Document medication administration and patient’s socket, the nurse may need to place two pads over the socket tolerance of procedure. Box 51-3 Administration of Eye Ointment 1. Explain procedure to patient. 2. Check medication for dosage, strength, side effects, contraindications, and expiration date. 3. Perform hand hygiene and apply gloves. 4. Instruct patient to tilt head backward and look up toward the ceiling. 5. Gently pull lower lid down to form a pocket into which ointment is placed. 6. Express ointment directly into exposed palpebral conjunctiva, moving from inner to outer canthus. Be careful not to touch patient’s eye or surrounding structure with tip of ointment tube. The tip of the ointment tube must remain sterile. FIGURE 51.11 (A) Morgan lens is used for eye irrigation. 7. Release lower eyelid over the ointment. (B) Irrigation of eye. Continued 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1224 1224 UNIT FOURTEEN Understanding the Sensory System The inner ear also has receptors for equilibrium: dynamic Box 51-3 Administration of Eye equilibrium receptors are within the semicircular canals whereas static equilibrium receptors are within the vestibule Ointment—cont’d (Fig. 51.14). Within the utricle and saccule of the v estibule, 8. Instruct patient to gently close eyes. the hair cells bend in response to gra vity on the otoliths as 9. Remove gloves. Perform hand hygiene. the position of the head changes. The impulses generated are 10. Explain that vision may be blurred while ointment carried by the vestibular branch of the eighth cranial nerve to is in the eye. the cerebellum, medulla, and pons. The cerebellum sends this 11. Document medication administration and patient’s information continuously to the cerebral motor corte x. The tolerance of procedure. cerebellum and brainstem use this information to maintain equilibrium at a subconscious level; the cerebrum interprets the conscious awareness of the position of the head. When the head moves, movement of the endolymph will to help the eyelids remain closed. The purpose of eye patching bend the cupula within the ampulla. The bending of the hair is to protect the eye from further damage by keeping the lids cells at its base generates impulses carried by the v estibular closed. Sometimes an additional metal shield is placed o ver branch of the eighth cranial nerv e to the cerebellum and the soft pads to protect the eye from external injury. The patch brainstem, and then impulses are sent to the cerebral cortex. is taped in place and the patient instructed to rest the eyes. The These impulses are interpreted as directional acceleration or nurse should suggest quiet activities, such as listening to music deceleration; this information is used to maintain equilibrium or an audio book, or sleeping. Watching television or reading during movement. is not recommended because the patched e ye follows the movement of the unpatched eye. Aging and the Ear In the ear, cumulative damage to the hair cells in the or gan of HEARING Corti usually becomes apparent sometime after the age of 60 (see Fig. 51.8). Damaged hair cells cannot be replaced. Ability Normal Anatomy and Physiology of the Ear to hear high frequencies is usually lost f irst (presbycusis), The ear consists of three areas: the outer ear, the middle ear, whereas hearing may still be adequate for lower pitched ranges. and the inner ear. The inner ear contains the receptors for the The high-pitched sounds f, s, k, and sh are common losses. Also, senses of hearing and equilibrium. it becomes more difficult to filter out background noises, so busy, loud environments make it difficult to hear conversations. Outer Ear The outer ear consists of the auricle and the auditory canal (Fig. 51.12). LEARNING TIP Middle Ear Presbycusis is the loss of hearing high-pitched The middle ear is an air -filled cavity in the temporal bone. sounds (pitch = cycles per second; loudness = Vibrations of the tympanic membrane caused by sound are decibels [dB]). Because the ability to hear pitch is transmitted through the three auditory bones (ossicles). The lost rather than loudness, it is not helpful to talk stapes then transmits vibrations to the fluid-filled inner ear at louder to a patient with this type of hearing loss. the oval window. In fact, talking louder can make it more difficult to discriminate sounds. It is important to know the Inner Ear type of hearing loss a patient has. The inner ear is a ca vity in the temporal bone called the bon y labyrinth, lined with membranes called the membranous labyrinth. The fluid between bone and membrane is called perilymph, and that within the membrane is called endolymph. Nursing Assessment of the Ear and Hearing The structures of the bon y labyrinth include the semicircular A quiet environment is helpful for collecting accurate hearing canals, vestibule, and cochlea (Fig. 51.13). data. Document the patient’s behavior because it may provide The process of hearing in volves the transmission of information related to hearing loss. vibrations and the generation of nerve impulses. When sound waves enter the auditory canal, vibrations are transmitted by Health History the following structures: tympanic membrane, malleus, incus, The patient’s self-appraisal of his or her hearing or related stapes, oval window of the inner ear, perilymph and endolymph symptoms is obtained during the health history. Data collection within the cochlea, and hair cells of the organ of Corti. When regarding symptoms includes asking the WHAT’S UP? the hair cells bend, they generate impulses that are carried by questions: where it is, how it feels, aggravating and alleviating the eighth cranial nerve to the brain. The auditory areas, for factors, timing, severity, useful data for associated symptoms, both hearing and interpretation, are in the temporal lobes of and perception of the problem by the patient. Symptoms the cerebral cortex. related to the ear that may be reported include decreased 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1225 Chapter 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing 1225 Outer Ear The auricle (pinna) is the visible Ossicles: part of the ear. Shaped by Malleus cartilage, this part of the ear Incus funnels sound into the auditory Stapes canal. Semicircular canals The auditory canal leads through the temporal bone to the eardrum. (The opening of the Vestibular nerve auditory canal to the outside of Cochlear nerve the body is called the external Cochlea acoustic meatus.) Glands lining the canal produce secretions that Round window mix with dead skin cells to form cerumen (ear wax). Cerumen waterproofs the canal and also traps dirt and bacteria. The cerumen usually dries and then, propelled by jaw movements Eustachian tube during eating and talking, works its way out of the ear. Outer ear Middle ear Inner ear Middle Ear Auditory ossicles: The three smallest bones in the body connect the eardrum to the inner ear; they are named for their shape: Malleus (hammer) Oval window Incus (anvil) Stapes (stirrup) The stapes fits within the oval window of the The auditory or eustachian tube vestibule, which is where the inner ear begins. is a passageway from the middle ear to the nasopharynx. Its purpose is to equalize pressure Tympanic membrane (or eardrum): on both sides of the tympanic This membranous structure separates the membrane. Unfortunately, it can outer ear from the middle ear; it vibrates also allow infection to spread freely in response to sound waves. from the throat to the middle ear. FIGURE 51.12 Outer and middle ear. From Thompson, G. S. (2013). Understanding anatomy and physiology. Philadelphia: F.A. Davis, p. 205. hearing or loss of hearing, otorrhea (discharge), otalgia (ear Family history related to ear disorders includes an y pain), itching, fullness, tinnitus (ringing, buzzing, or roaring in hearing problems or hearing loss and f amily members the ears), or vertigo (dizziness). with Ménière’s disease. Significant findings are recorded, Information about current and past medications is obtained. including the patient’s relationship to the f amily member Many medications are potentially toxic to the ear and can cause with the problem. hearing loss or decreased hearing. P ay particular attention to Information about the patient’ s care of the ears is also any exposure to medications that are potentially ototoxic, such gathered. It is important to assess what preventive measures as certain antibiotics or diuretics (see Chapter 52). the patient practices and what the patient’s learning needs are Ask about hearing aids or assistive hearing de vices, concerning care and protection of the ears. Determine ho w surgeries, treatments, aller gies, sodium and alcohol intak e the patient cleans the ears, any exposure to loud noises during (which can affect the amount of endolymph in the inner ear), and childhood illnesses including mumps, measles, or scarlet fever. Also ask about recent upper respiratory infections, history WORD BUILDING of infections, injury to the ear , hospitalizations, swimming otorrhea: oto—related to the ear + rrhea—to flow habits, exposure to pressure changes (flying or diving), medical otalgia: ot—related to the ear + algia—signifying pain diseases, and any recent or past exposure to any loud noises. ototoxic: oto—related to the ear + toxic—poison 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1226 Inner Ear Vestibular Cochlear duct nerve Perilymph (with endolymph) Semicircular canals: These structures Resting on are crucial for the the floor maintenance of (called the equilibrium and basilar Cochlear balance. membrane) nerve of this duct is the organ Vestibule: of Corti, the This structure, hearing which marks sense organ. the entrance to the labyrinths, Oval contains organs window necessary for Tectorial the sense of Hairs membrane balance. Round The organ of Corti window consists of a layer of epithelium (composed Cochlea: of sensory and This snail-like supporting cells). structure The spirals of the Thousands of hair contains the cochlea are divided cells project from this structures for into three epithelial layer and hearing. compartments. The are topped with a middle compartment gelatin-like membrane is a triangular duct called the tectorial (called the cochlear membrane. Nerve duct) filled with Supporting cells fibers extending from endolymph; the outer the base of the hairs two compartments Basilar membrane eventually form the are filled with cochlear nerve perilymph. Fibers of cochlear nerve (cranial nerve VIII). FIGURE 51.13 Inner ear. From Thompson, G. S. (2013). Understanding anatomy and physiology. Philadelphia: F.A. Davis. p. 206. Otoliths Three fluid-filled semicircular canals Gelatinous lie at right angles to matrix one another. This arrangement allows Hair cell each canal to be stimulated by a different movement of the head. Nerve fibers Inside the vestibule are two sense organs: the utricle and saccule. A patch of hair cells lies inside both these organs. The tips of the hair cells are covered by a gelatin-like material; embedded throughout the gelatin material are heavy mineral crystals called otoliths. At the end of each canal is a Cupula bulb-like area called an ampulla. Within each ampulla is a mound of hair cells topped by a Hair cells gelatinous cone-shaped cap called the cupula. The lightweight cupula floats in the endolymph Sensory that fills the semicircular canals. nerve fibers FIGURE 51.14 Balance. From Thompson, G. S. (2013). Understanding anatomy and physiology. Philadelphia: F.A. Davis, p. 208. 4068_Ch51_1211-1235 15/11/14 2:22 PM Page 1227 Chapter 51 Sensory System Function, Assessment, and Therapeutic Measures: Vision and Hearing 1227 recreational or work activities, any changes in ability to hear, bre