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Chapter 11 Special Senses: Eyes and Ears Related Combining Forms Structure Related Combining Forms Eyes opt/I, opt/o, optic/o, ophthalm/o Iris ir/i, ir/o, irid/o, irit/o Lens phac/o, phak/o Retina retin/o Lacrimal apparatus dacryocyst/o, lacrim/o Ears acous/o, acoust/o, audi/o, audit/o, ot/o Outer ear pinn/i Middle ear myring/o, tympan/o Inner ear labyrinth/o Functions of Eyes • Receptor organs of sight • Receive images and transmit them to the brain Structures of the Eyes • Eyeball • Adnexa Structures of Eyes Adnexa of Eyes • Structures outside the eyeball – Orbit – Eye muscles – Eyelids – Eyelashes – Conjunctiva – Lacrimal apparatus Orbit • Bony cavity of skull that contains and protects the eyeball and associated muscles, blood vessels, and nerves Muscles of Eye Muscles of Eye • Six major eye muscles (three pairs) – Superior and inferior oblique muscles – Superior and inferior rectus muscles – Lateral and medial rectus muscles • Allow for wide range of precise eye movements Muscles of Eye • Binocular vision – Coordination of eye muscles allowing for depth perception • (bin-: two; ocul: eye) • Depth perception – Ability to see things in three dimensions Eyelids, Eyebrows, and Eyelashes • Provide protection from foreign matter, excessive light, and injuries • Canthus – Angle where upper and lower eyelids meet • (canth: corner of the eye) • Cilia – Small hair making up eyebrows/eyelashes Eyelids, Eyebrows, and Eyelashes • Tarsus – Framework within upper and lower eyelids providing necessary stiffness and shape • (tars: edge of eyelid) Conjunctiva Conjunctiva • Transparent mucous membrane lining underside of the eyelid protecting the exposed surface of the eyeball Lacrimal Apparatus • Structures producing, storing, and removing tears • Lacrimal glands – Located on underside of upper eyelid just above outer corner of each eye • Lacrimal fluid – Maintains moisture on the anterior surface of eyeball Lacrimal Apparatus • Lacrimal canal – Ducts at the inner corner of each eye – Ducts collect tears emptying them into lacrimal sacs • Lacrimal sac – Enlargement of the upper portion of the lacrimal duct • Lacrimal duct – Passageway draining excess tears into nose Eyeball • One-inch sphere with only about 1/6th of its surface visible • Ocular – Pertaining to the eye • Extraocular – Outside the eyeball • Intraocular – Within the eyeball Walls of Eyeball Walls of Eyeball • Three layers – Sclera • White of the eye • Maintains shape of eye • Protects delicate inner layers of tissue – Choroid • Opaque middle layer of eyeball • Provides blood supply to the entire eye Walls of Eyeball • Three layers – Retina • Innermost layer lining posterior segment of the eye • Receives nerve impulses and transmits them to the brain via optic nerve Anterior Segment of Eyeball Anterior Segment of Eyeball • Anterior segment – Front one-third of eyeball – Located behind the cornea and in front of the iris – Aqueous humor helps maintain shape and nourishes intraocular structures – Intraocular pressure measures fluid pressure inside the eye which is regulated by rate at which aqueous humor enters/leaves the eye Posterior Segment of Eyeball • Posterior segment – Remaining two-thirds of the eyeball – Located behind the iris and in front of the ligaments holding the lens in place – Lined with the retina – Filled with vitreous humor – Fibers attached to the surface of retina help maintain the shape of the eye Structures of Retina • Rods and cones – Receive images that have passed through lens – Images convert into nerve impulses and transmit to brain via optic nerve – Rods • Black and white receptors – Cones • Color receptors Structures of Retina • Macula – Light-sensitive area in the center of the retina – Responsible for sharp central vision • Fovea centralis – Pit in the middle of the macula – High concentration of cones allows for the best color vision Structures of Retina • Optic disk – Where nerve endings of the retina enter optic nerve – Blind spot – Contains no rods or cones • Optic nerve – Transmits nerve impulses from retina to the brain Uvea • Pigmented layer of eye • Rich blood supply • Consists of choroid, ciliary body, and iris Ciliary Body • Set of muscles and suspensory ligaments that adjust thickness of the lens and refine the focus of light rays on retina • Produces aqueous humor • To focus on nearby objects, muscles adjust the lens to make it thicker • To focus on distant objects, muscles stretch lens to make it thinner Iris • Colorful circular structure surrounding the pupil • Muscles control the amount of light entering through the pupil • Muscles contract allowing smaller opening to decrease the amount of light entering eye • Muscles relax allowing larger opening to increase the amount of light entering eye Cornea, Pupil, and Lens • Cornea – Transparent outer surface of eye covering iris and pupil – Focuses light rays entering the eye • Pupil – Black circular opening in the center of the iris permitting light to enter the eye Cornea, Pupil and Lens • Lens – Clear, flexible, curved structure contained within clear capsule located behind the iris and pupil – Focuses images on the retina Normal Action of Eyes • Accommodation – Eye adjustment for the vision at varying distances • Convergence – Simultaneous inward movement of eyes toward each other – Allows maintenance of single binocular vision as object comes nearer Normal Action of Eyes • Emmetropia – Normal vision • (emmetr: proper measure) • Refraction – Bending of light rays to focus on the retina • Visual acuity – Ability to distinguish object details and shape at a distance Medical Specialties Related to Eyes • Ophthalmologist – Specializes in diagnosing/treating diseases/disorders of eyes • (ophthalm: eye) • Optometrist – Provides diagnosis of eye diseases, measuring accuracy of vision determining need for corrective lenses • (opt/o: vision) Medical Specialties Related to Eyes • Optician – Health care practitioner who designs, fits, and dispenses lenses for vision correction Pathology of Eyes and Vision: Eyelids • Ptosis – Drooping of upper eyelid • Chalazion – Nodule or cyst related to obstruction in sebaceous gland • Blepharitis – Swelling of eyelid, near eyelash follicles • (blephar: eyelid) Pathology of Eyes and Vision: Eyelids Pathology of Eyes and Vision: Eyelids • Ectropion – Turning outward (eversion) of the edge of the eyelid • Entropion – Turning inward (inversion) of the edge of the eyelid • Hordeolum – Pus-filled lesion on the eyelid due to acute infection in sebaceous gland Pathology of Eyes and Vision: Eyelids • Periorbital edema – Swelling of tissue surrounding the eye(s) • (peri-: around; orbit: eyeball) – Associated with allergic reaction Additional Adnexa Pathology • Conjunctivitis – Inflammation of conjunctiva usually due to infection or allergy – Pinkeye • Dacryoadenitis – Inflammation of lacrimal gland due to bacterial, viral, or fungal infection • (dacry/o: tear) Additional Adnexa Pathology • Subconjunctival hemorrhage – Bleeding between conjunctiva and sclera – Usually due to injury • Xerophthalmia – Dry eye due to decreased production of tears by tear glands – May be related to aging, systemic diseases or Vitamin A deficiency • (xer: dry) Uvea, Cornea, Iris, and Sclera • Uveitis – Inflammation of uvea • (uve: uvea) • Iritis – Form of uveitis affecting structures in the front of the eye • Corneal abrasion – Injury to outer layers of cornea • (corne: cornea) Uvea, Cornea, Iris, and Sclera • Corneal ulcer – Pitting of cornea due to infection or injury • Diabetic retinopathy – Damage to retina as complication of uncontrolled diabetes Uvea, Cornea, Iris, and Sclera • Keratitis – Inflammation of cornea – May be bacterial, viral, or fungal • (kerat: cornea) • Keratoconus – Irregular, cone-shaped cornea leading to distortion of vision Uvea, Cornea, Iris, and Sclera • Scleritis – Inflammation of sclera – May be associated with infections, chemical injuries, or autoimmune diseases • (scler: white of the eye) Eye • Anisocoria – Unequal size of pupils – May be congenital, or related to head injury, aneurysm, or pathology of CNS • (anis/o: unequal; cor: pupil) • Cataract – Loss of transparency of lens causing progressive loss of visual clarity Eye • Floaters – Particles of cellular debris in vitreous humor casting shadows on the retina – Occur normally – May be an indication of retinal detachment • Photopsia – Appearance of flashes of light • (phot: light; -opsia: view of) Eye • Miosis – Contraction of pupil in response to light – May be due to prescription or illegal drugs • (mio: smaller) • Mydriasis – Dilation of pupil – May be due to diseases, trauma, or drugs • (midrias: dilation of pupil) Eye • Nystagmus – Involuntary, constant, rhythmic movement of eyeball – Congenital, or due to neurological injury or drug use • Papilledema – Swelling and inflammation of the optic nerve at the point of entrance into eye through optic disk • (papill: nipplelike) Eye Eye • Retinal detachment – Separation of some or all of the retina from the choroid – Lack of treatment leads to blindness • Retinitis pigmentosa – Progressive degeneration of retina affecting night and peripheral vision – Appears as dark pigmented spots on retina Glaucoma • Group of diseases characterized by increased intraocular pressure resulting in damage to the retinal nerve fibers and optic nerve • Open-angle glaucoma – More common form – Detected through regular eye examinations – Asymptomatic until optic nerve is damaged Glaucoma • Closed-angle glaucoma – Narrowing of area between cornea and iris resulting in decreased fluid to trabecular meshwork – Sudden pain, nausea, redness of eye, and blurred vision – Lack of treatment leads to blindness in as little as 2 days Macular Degeneration • Progressive condition causing damage to the macula • Results in the loss of central vision – (macul: spot) • Types: – Age-related macular degeneration – Dry macular degeneration – Wet macular degeneration Functional Defects • Diplopia – Perception of two images of a single object • Hemianopia – Blindness in one-half of the visual field • (hemi-: half) • Monochromatism – Inability to distinguish certain colors • (mon/o: one; chromat: color) Functional Defects • Nyctalopia – Difficulty seeing at night, although normal daytime vision • (nyctal: night) • Photophobia – Excessive sensitivity to light • (phot/o: light) Functional Defects • Presbyopia – Decline of near vision related to aging • (presby: old age) Strabismus • Improper eye alignment due to the inability of eye muscles to coordinate • Esotropia – Inward deviation of one or both eyes • (eso-: inward; trop: turn) • Exotropia – Outward deviation of one eye or both eyes • (exo: outward) Refractive Disorders • Ametropia – Images do not focus properly on retina – Includes astigmatism, hyperopia, and myopia • (ametr: out of proportion) • Astigmatism – Lack of focus due to uneven curvature of cornea Refractive Disorders • Hyperopia – Light rays focus beyond the retina – Farsightedness • Myopia – Light rays focus in front of the retina – Nearsightedness Blindness • Inability to see • Legal blindness – Best-corrected vision of 20/200 • Amblyopia – Dimness of vision without any detectable disease of eyes • (ambly: dim or dull) Blindness • Scotoma – Abnormal area of diminished vision surrounded by area of normal vision Diagnostic Procedures for Vision and Eyes • Snellen chart – Measures visual acuity – Recorded as fraction with 20/20 representing normal vision • First number: standard distance from the chart • Second number: deviation from the norm • Refraction – Determines refractive error – Determines corrective lens prescription Diagnostic Procedures for Vision and Eyes • Diopter – Unit of measurement of the lens' refractive power • Cover test – Determines how eyes work together – Assesses binocular vision • Visual field testing – Determines loss in peripheral vision Diagnostic Procedures for Eyes • Ophthalmoscopy – Use of ophthalmoscope to visually examine fundus of the eye • Dilation – Artificial enlargement of pupil to examine the interior of the eyes • Mydriatic drugs – Force eyes to remain dilated in the presence of bright light Diagnostic Procedures for Eyes • Slit-lamp ophthalmoscopy – Focusing the beam of light onto parts of the eye to permit examination of structures at front of the eye such as the cornea, iris, and lens • Fluorescein staining – Application of fluorescent dye to the surface of the eye via eye drops – Causes corneal abrasion to appear bright green Diagnostic Procedures of Eyes • Fluorescein angiography – Radiographic study of blood vessels in the retina after injecting fluorescein dye • PERRLA (Pupils are Equal, Round, Responsive to Light and Accommodation) – Diagnostic observation – Abnormality could indicate head injury or damage to the brain Diagnostic Procedures of Eyes • Tonometry – Measurement of intraocular pressure – Abnormally high pressure may indicate glaucoma • (ton/o: tension) Treatment Procedures of Eyes and Vision • Orbit and Eyelids – Orbitotomy • Surgical incision into orbit for biopsy, abscess drainage, or removal of tumor/foreign object – Tarsorrhaphy • Partial or complete suturing together of upper and lower eyelids when lids are paralyzed and unable to close normally – (tars/o: eyelid) Treatment Procedures of Eyes and Vision • Conjunctiva and Eyeball – Corneal transplant • Surgical replacement of scarred/diseased cornea with clear corneal tissue from donor – Enucleation • Removal of eyeball, leaving the eye muscles intact – (e-: out of; nucle: nucleus; -ation: action) – Ocular prosthesis • Artificial eye fitting over or replacing malformed eye Treatment Procedures of Eyes and Vision • Conjunctiva and Eyeball – Iridectomy • Surgical removal of a portion of the iris – (irid: iris) – Radial keratotomy • Surgical treatment of myopia to bring focal point closer to retina improving distance vision Treatment Procedures of Eyes and Vision • Conjunctiva and Eyeball – Scleral buckle • Repairing of detached retina – Vitrectomy • Removal of vitreous humor and replacing with clear solution Cataract Surgery • Lensectomy – Surgical removal of cataract-clouded lens • Phacoemulsification – Ultrasonic vibration to shatter and remove lens clouded by cataract • Intraocular lens – Surgically implanted replacement of natural lens Corrective Lenses • Correct refractive errors – Concave lenses • Curved inward • Used for myopia – Convex lenses • Curved outward • Used for hyperopia • May have two refractive powers (bifocal) or three refractive powers (trifocal) Corrective Lenses • Contact lenses – Float on tear film in front of eye – Rigid gas-permeable lenses cover central part of the cornea – Disposable soft lenses cover entire cornea Laser Treatments of Eyes • Laser iridotomy – Focused light beam is used to create a hole in the iris – Treatment of closed-angle glaucoma • Laser trabeculoplasty – Creates opening in the trabecular meshwork allowing proper drainage of fluid Laser Treatments of Eyes • LASIK (Laser-Assisted In Situ Keratomileusis) – Treats vision conditions caused by the shape of cornea • (-mileusis: carving) • Photocoagulation – Use of laser to treat some forms of wet macular degeneration or to repair small retinal tears Laser Treatments of Eyes • Retinopexy – Reattaches retinal detachment Functions of Ear • Receptor organ of hearing • Receives sound impulses and transmit them to the brain • Inner ear helps maintain balance • Auditory – Pertaining to sense of hearing • Acoustic – Pertaining to sound or hearing Structures of Ear Structures of Ear • Three separate regions – Outer ear – Middle ear – Inner ear Outer Ear • Pinna – Also known as auricle – External portion of the ear – Captures sound waves and transmits them into external auditory canal • External auditory canal – Transmits sound waves to tympanic membrane of the middle ear Outer Ear • Cerumen – Earwax – Secreted by ceruminous glands lining auditory canal – Protective substance that traps small insects, dust, debris, and bacteria Middle Ear • Transmits sound across space between outer ear and inner ear • Tympanic – Eardrum – Located between outer and middle ear – Membrane transmits sound by vibrating • (Myring/o and tympan/o: tympanic membrane) Middle Ear • Mastoid process – Temporal bone containing hollow air space surrounding the middle ear • Auditory Ossicles – Transmit sound waves from eardrum to inner ear by vibration – Malleus (hammer) – Incus (anvil) – Stapes (stirrup) Middle Ear • Eustachian Tubes – Lead from middle ear to nasal cavity and throat – Equalize air pressure within the middle ear with that of the outside atmosphere Inner Ear • Contains sensory receptors for hearing and balance • Structures present in the inner ear are known as labyrinth • Oval window – Located under the base of stapes – Membrane separating the middle ear from the inner ear – Allows entrance of vibrations into inner ear Inner Ear • Cochlea – Snail-shaped structure where sound vibrations are converted into nerve impulses – Contains cochlear duct, organ of Corti, semicircular canals, and acoustic nerves • Organ of Corti – Relays vibrations to auditory nerve fibers that transmit sound to the auditory center of the cerebral cortex for interpretation Inner Ear • Semicircular canals – Three – Contain endolymph and sensitive hair cells the bend in response to the movements of head – Assist with equilibrium Inner Ear • Acoustic nerves – Transmit information to the brain – Two parts • Cochlear nerves transmit sound for hearing • Vestibular nerves sense balance and head position Normal Action of Ears • Air conduction – Process of sound waves entering the ear through pinna and traveling down the external auditory canal to strike tympanic membrane • Bone conduction – Occurs as eardrum vibrates causing auditory ossicles to vibrate Normal Action of Ears • Sensorineural conduction – Occurs when sound vibrations reach inner ear – Structures receive sound waves and relay them to the auditory nerve for transmission to the brain Medical Specialties Related to Ears • Audiologist – Specializes in measurement of hearing function and in rehabilitation of persons with hearing impairments • (audi: hearing) • Speech-language pathologist – Assists patients with problems related to swallowing, speech, and communication disorders Pathology of Ears and Hearing • Outer ear – Impacted cerumen • Accumulation of earwax forming solid mass and adhering to the walls of external auditory canal – Otalgia • Pain in the ear – (ot: ear; -algia: pain) – Otitis • Inflammation of the ear Pathology of Ears and Hearing • Outer ear – Otomycosis • Fungal infection of the external auditory canal – (myc: fungus) – Otopyorrhea • Flow of pus from the ear Pathology of Ears and Hearing • Outer ear – Otorrhea • Any discharge from the ear – Otorrhagia • Bleeding from the ear Pathology of Ears and Hearing • Middle ear – Barotrauma • Pressure-related ear condition caused by pressure changes – Cholesteatoma • Epidermal cyst in middle ear and/or mastoid process made of epithelial cells and cholesterol – (cholesteat: cholesterol) Pathology of Ears and Hearing • Middle ear – Mastoiditis • Inflammation of any part of mastoid bone – Infectious myringitis • Contagious inflammation causing blisters on eardrum – Otitis media • Inflammation of middle ear Pathology of Ears and Hearing • Middle ear – Otosclerosis • Ankylosis of bones of middle ear • Results in conductive hearing loss • Treatment: stapedectomy Pathology of Ears and Hearing • Inner ear – Labyrinthitis • Inflammation of labyrinth • May result in vertigo and deafness – Vertigo • Sense of dizziness and loss of balance – Benign paroxysmal positional vertigo • Occurs with the shift in the location of the small crystals in semicircular canals Pathology of Ears and Hearing • Inner ear – Meniere's disease • Amount of fluid in inner ear increases intermittently, producing vertigo, fluctuating hearing loss, and tinnitus – Tinnitus • Ringing, buzzing, or roaring sound in one or both ears • May be associated with prolonged exposure to loud noises Pathology of Ears and Hearing • Hearing loss – Acoustic neuroma • Brain tumor adjacent to the cranial nerve – Deafness • Complete or partial loss of ability to hear – Presbycusis • Gradual loss of sensorineural hearing related to aging – (-cusis: hearing) Pathology of Ears and Hearing • Hearing loss – Conductive hearing loss • Sound waves are prevented from passing air to fluid-filled inner ear – Sensorineural hearing loss • Due to damage to auditory nerve or hair cells in inner ear Diagnostic Procedures of Ears and Hearing • Audiological evaluation – Measurement of the ability to hear and understand speech sounds based on pitch and loudness • Audiometry – Use of audiometer to measure hearing acuity • (audi/o: hearing) Diagnostic Procedures of Ears and Hearing • Otoscope – Instrument used to examine external ear canal • Monaural testing – Involves one ear • (mon-: one; aur: hearing) • Binaural testing – Involves both ears • (bin-: two) Diagnostic Procedures of Ears and Hearing • Tympanometry – Use of air pressure in ear canal for testing the disorders of middle ear • Acoustic reflectometry – Tests for sound reflection from eardrum determining amount of fluid in middle ear • Weber and Rinne tests – Use of tuning fork to distinguish between conductive and sensorineural hearing losses Treatment Procedures of Ears and Hearing • Outer ear – Otoplasty • Surgical repair, restoration, or alteration of pinna • Middle ear – Ear tubes (tympanostomy tubes) • Ventilating tubes inserted into the eardrum to provide drainage for fluid and relief of pressure Treatment Procedures of Ears and Hearing • Middle ear – Mastoidectomy • Surgical removal of mastoid cells – Myringotomy • Surgical incision in eardrum to relieve pressure – Stapedectomy • Surgical removal of the top portion of the stapes and insertion of prosthetic device Treatment Procedures of Ears and Hearing • Middle ear – Tympanoplasty • Surgical correction of damaged middle ear • Inner ear – Labyrinthectomy • Surgical removal of all or portion of labyrinth – Vestibular rehabilitation therapy • Physical therapy to treat variety of balance disorders Treatments for Hearing Loss • Assistive listening device – Transmits, processes, or amplifies sound – Used with or without hearing aid • Cochlear implant – Bypasses damaged portion of ear and directly stimulates auditory nerve • Fenestration – New opening in the labyrinth to restore hearing Treatments for Hearing Loss • Hearing aids – Electronic devices worn to correct hearing loss – Analog hearing aid • Uses microphone to detect/amplify sounds – Digital hearing aid • Computer chip converts incoming sound into code that is filtered before being amplified