CH 11: Special Senses of the Eye and Ear

Ophthalmologist

Medical doctor who diagnoses and treats diseases of the eye.

Otorhinolaryngologist (ENT)

Physician specializing in ear, nose, and throat disorders.

Audiologist

Professional who evaluates hearing function.

Conjunctiva

Transparent mucous membrane lining the inside of the eyelids that helps keep the eye moist.

Lacrimal apparatus

Structures that produce and drain tears; lacrimal glands secrete tears, lacrimal sacs collect them, and nasolacrimal ducts drain them into the nose.

Extrinsic eye muscles

Six muscles per eye that coordinate eye movements and alignment.

Stereopsis

Three-dimensional depth perception that depends on proper alignment of both eyes.

Sclera

Tough white outer layer of the eye that protects internal structures.

Cornea

Transparent front surface of the eye that bends incoming light and has no blood vessels.

Iris

Colored part of the eye that controls pupil size and the amount of light entering.

Ciliary body

Structure that changes lens shape to focus on near or distant objects (accommodation).

Choroid

Vascular middle layer of the eye that nourishes tissues and absorbs stray light.

Retina

Inner neural layer at the back of the eye that converts light into nerve impulses.

Aqueous humor

Fluid filling the anterior cavity of the eye in front of the lens.

Vitreous humor

Gel-like substance filling the large cavity behind the lens.

Rods

Retinal photoreceptors that detect light in dim conditions but do not detect color.

Cones

Retinal photoreceptors responsible for color vision and sharp visual acuity.

Optic nerve

Nerve carrying visual impulses from the retina toward the brain.

Optic disc (blind spot)

Site where the optic nerve leaves the retina; contains no rods or cones.

Macula lutea

The central retinal area

Fovea centralis

Region in the retina with densely packed cones to provide the sharpest vision

Refraction

Bending of light by the cornea and lens to focus an image on the retina.

Emmetropia

Normal refractive condition in which images focus sharply on the retina.

Conjunctivitis (pink eye)

Inflammation of the conjunctiva; infectious cases can be contagious, while allergies and irritants can also cause it.

Stye (hordeolum)

Infection of an eyelash follicle that produces a localized abscess.

Ptosis (blepharoptosis)

Drooping of the upper eyelid, which may result from muscle weakness or excess tissue.

Dry eye disease

Insufficient tear production causing eye discomfort and possible corneal or conjunctival damage.

Sjogren syndrome

Autoimmune disorder affecting tear and salivary glands, causing dry eyes and dry mouth.

Strabismus

Misalignment of the eyes due to imbalance in eye muscle control.

Esotropia

Type of strabismus in which an eye turns inward.

Exotropia

Type of strabismus in which an eye turns outward.

Amblyopia (lazy eye)

Reduced vision in one eye because the eye and brain do not develop normal visual cooperation; may be treated by patching the stronger eye.

Nystagmus

Rapid involuntary eye movements that can be horizontal, vertical, or rotary.

Corneal abrasion

Scratch or injury to the corneal surface, sometimes caused by foreign objects or contact lenses.

Anisocoria

Unequal pupil sizes, which can be harmless or associated with neurological injury.

Uveitis

Inflammation of the uvea (iris, ciliary body, and choroid), often causing pain and blurred vision.

Glaucoma

Eye disorder involving optic nerve damage, often associated with increased intraocular pressure from impaired fluid drainage.

Cataract

Clouding of the eye's lens that causes blurred vision and light sensitivity.

Macular degeneration

Damage to the central macula causing loss of sharp central vision, often with a dark or blurry central spot.

Retinal detachment

Separation of the retina from underlying tissue, potentially causing a dark shadow in peripheral vision; a surgical emergency.

Diabetic retinopathy

Retinal blood vessel damage associated with diabetes that can cause bleeding and vision loss.

Papilledema

Swelling of the optic disc caused by increased intracranial pressure.

Hyperopia (farsightedness)

Near objects appear blurry because light focuses behind the retina, often due to a shortened eyeball.

Myopia (nearsightedness)

Distant objects appear blurry because light focuses in front of the retina, often due to an elongated eyeball.

Presbyopia

Age-related loss of lens flexibility that makes focusing on near objects difficult.

Astigmatism

Blurred vision caused by irregular curvature of the cornea that prevents even focusing of light.

Visual acuity

Sharpness or clarity of vision.

PERRRLA

Pupils equal, round, reactive to light and accommodation; a routine pupillary assessment.

Snellen chart

Letter chart used to test distance vision, usually at 20 feet.

Fluorescein staining

Eye examination using dye to reveal corneal abrasions or ulcers.

Fundoscopy (ophthalmoscopy)

Examination of the retina and interior of the eye using an ophthalmoscope.

Slit-lamp examination

Magnified eye examination used to identify corneal abnormalities and other eye diseases.

Tonometry

Measurement of intraocular pressure, particularly useful in glaucoma evaluation.

Photocoagulation / retinal cryopexy

Laser treatment or freezing used to seal retinal tears or help treat retinal damage.

Phacoemulsification

Cataract procedure using ultrasound to break up the cloudy lens before replacing it with an artificial lens.

Mydriatics

Medications that dilate the pupil, like eye drops

Miotics

Medications that constrict the pupil, like eye drops

Auricle (pinna)

Visible outer ear that directs sound into the external auditory canal.

Tympanic membrane (eardrum)

Membrane that vibrates when sound waves strike it, passing vibrations to the middle ear.

Ossicles (malleus, incus, stapes)

Three tiny middle-ear bones that amplify and transmit sound vibrations to the oval window.

Eustachian (auditory) tube

Tube connecting the middle ear to the nasopharynx to help equalize air pressure.

Cochlea

Fluid-filled inner-ear structure containing hair cells that convert sound vibrations into nerve impulses.

Oval window and round window

Oval window receives vibrations from the stapes; round window releases excess pressure in the cochlea.

Vestibule and otoliths

Inner-ear balance structures containing crystals that help detect head tilt and linear position changes.

Semicircular canals

Three fluid-filled inner-ear canals that detect rotational movements of the head.

Otitis externa

Bacterial or fungal infection of the external auditory canal.

Acute otitis media (AOM)

Middle-ear infection with fluid, ear pain, fever, and a red tympanic membrane, often after an upper respiratory infection.

Otitis media with effusion (OME)

Persistent fluid in the middle ear due to impaired drainage through the Eustachian tube, which may reduce hearing.

Cholesteatoma

Abnormal collection of growing skin cells in the middle ear that can damage ossicles and surrounding structures.

Otosclerosis

Abnormal bone growth near the stapes and oval window that limits vibration and causes gradual hearing loss.

Sensorineural hearing loss

Hearing loss caused by damage to inner-ear hair cells or auditory nerves, often related to aging or loud noise exposure.

Vertigo

False sensation of spinning or movement.

Tinnitus

Perception of ringing, buzzing, hissing, or other sounds without an external source.

Benign paroxysmal positional vertigo (BPPV)

Brief positional vertigo caused when displaced otolith fragments enter the semicircular canals.

Weber test

Tuning-fork hearing test that checks which ear hears the sound more strongly.

Rinne test

Tuning-fork test comparing air conduction with bone conduction of sound.

Audiometry

Hearing test using sounds of different frequencies and intensities, producing a record of hearing responses.

Tympanometry

Test that changes pressure in the ear canal to assess movement and function of the tympanic membrane and middle ear.

Myringotomy

Small incision in the eardrum, sometimes with a ventilation tube, to drain middle-ear fluid.

Cochlear implant

Electronic device used in severe hearing loss to stimulate the auditory nerve.

Otolith repositioning procedure

Head-positioning treatment that moves displaced crystals out of the semicircular canals to relieve BPPV.