Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Timby/Smith: Introductory Medical-Surgical Nursing, 11/e Chapter 41: Introduction to the Sensory System

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Anatomy and Physiology of the Eyes Extraocular Structures –Eyelids, eyelashes, tears: protect the eye –Canthus: where eyelids meet; usually horizontal; Down syndrome; epicanthal fold –Blinking: clears dust and particles from eye surface –Eyelids: adjust amount of light entering eyes; distribute tears; multiple glands; conjunctiva; caruncle; lacrimal apparatus –Tears: water, sodium chloride, and lysozyme

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Is the following statement true or false? The eyelids, eyelashes, and tears are responsible for clearing dust and particles from eye surface.

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer False Rationale: Blinking clears dust and particles from eye surface; and the eyelids, eyelashes, and tears are responsible for protection of the eye.

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Intraocular Structures Three Layers –Sclera (white of the eye) Protects structures within the eye Connects to cornea, anterior chamber, pupil –Uvea (vascular coat of the eye) Choroid, iris, pupil, aqueous humor, vitreous humor –Retina Rods and cones; macula

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Is the following statement true or false? Rods and cones are located in the retina of the eye.

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer True Rationale: Rods and cones are located in the retina of the eye.

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Visual Function Light  nerve signals: interpreted in cerebral cortex Refraction; rods, cones  optic nerve; accommodation Near point; cataract: opaque lens; blurred, cloudy images

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Nursing Assessment Client History –Allergy, vision changes, discomfort, corrective lenses –Eye medications; eye trauma, disease, surgery –Family history of eye disease Physical Assessment –Symmetry –Inflammation; exudate –Pupil constriction

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Eye Assessment Visual Screening Tests –Snellen eye chart: visual acuity –Jaeger chart; Rosenbaum Pocket Vision Screener: near vision –Ishihara polychromatic plates: color vision Extraocular Muscle Function Tests –Corneal light reflex test: eye alignment –Cover–uncover test: extraocular muscle function –Positions test: eye muscle strength, cranial nerve function

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Is the following statement true or false? The Snellen chart assesses for color vision.

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer False Rationale: Snellen eye chart determines visual acuity, whereas Ishihara polychromatic plates assess color vision.

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Diagnostic Studies Ophthalmoscopy: examination of fundus Retinoscopy: focusing power of each eye Tonometry: intraocular pressure –Normal IOP: 10 to 21 mm Hg Visual Field Examination –Peripheral vision; gaps –Visual field change associations: glaucoma, stroke, brain tumor, retinal detachment Color vision testing: color differentiation ability

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Diagnostic Studies—(cont.) Amsler grid: macular problems Slit-lamp examination: magnifies eye surface –Identifies: corneal abrasions, iritis, cataracts, conjunctivitis Retinal angiography: vascular changes, blood flow Ultrasonography: used when posterior of eye is difficult to visualize Retinal imaging: high resolution; pupil dilation unnecessary

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Anatomy and Physiology of the Ears Subdivisions of the ear: outer, middle, inner –Outer ear (Auricle) Pinna, external acoustic meatus, tympanic membrane –Middle ear Eustachian tubes, malleus, incus, stapes –Inner ear (labyrinth) Cochlea (hearing), semicircular canals (balance), vestibulocochlear nerve (cranial nerve VIII, organ of Corti

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Where is the pinna of the ear located? A) Outer B) Middle C) Inner D) Outer and middle

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer A) Outer Rationale: The pinna is located in the outer ear.

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Ear Assessment Basic Auditory Acuity Tests –Whisper test: gross auditory acuity Otoscopic examination: external acoustic canal, tympanic membrane inspection Tuning Fork Tests –Conductive or sensorineural hearing loss –Rinne test, Weber test Romberg Test: ability to sustain balance

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Diagnostic Studies Audiometry: precise measurement of hearing acuity; measured in decibels (dB) –Lowest perceptible sound perceived: 20 dB –Painful sound level: 120 dB Caloric stimulation test  nystagmus –Measures vestibular reflexes of inner ear Electronystagmography: vestibular function –Used in conjunction with caloric stimulation test –Measures duration and velocity of eye movements during nystagmus