Eye and Ear

Ocular Combining Forms and Terminology

• ambly/o: Dull or dim (e.g., amblyopia).

• aque/o: Water (e.g., aqueous).

• blephar/o: Eyelid (e.g., blepharitis).

• chromat/o: Color (e.g., chromatin).

• conjunctiv/o: Conjunctiva (e.g., conjunctivitis).

• corne/o: Cornea (e.g., corneal).

• cycl/o: Ciliary muscle (e.g., cyclic).

• dacry/o: Tear; tear duct (e.g., dacryocele).

• dipl/o: Double (e.g., diplopia).

• emmetr/o: Correct (e.g., emmetropia).

• glauc/o: Gray (e.g., glaucoma).

• ir/o / irid/o: Iris (e.g., iritis, iridotomy).

• kerat/o: Cornea (e.g., keratitis).

• lacrim/o: Tears (e.g., lacrimal).

• macul/o: Macula lutea (e.g., macular).

• mi/o: Lessening (e.g., miosis).

• mydr/i: Widening (e.g., mydriasis).

• nyctal/o: Night (e.g., nyctalopia).

• ocul/o / ophthalm/o: Eye (e.g., ocular, ophthalmic).

• opt/o / optic/o: Eye, vision (e.g., optic, optical).

• papill/o: Optic disk (e.g., papillitis).

• phac/o: Lens (e.g., phaclytic).

• phot/o: Light (e.g., photophobia).

• presby/o: Old age (e.g., presbyopia).

• pupill/o: Pupil (e.g., pupillary).

• retin/o: Retina (e.g., retinal).

• scler/o: Sclera (e.g., scleritis).

• stigmat/o: Point (e.g., stigmatosis).

Gross Anatomy and Exterior Protective Structures of the Eye

• Pupil: The opening in the center of the iris where light enters the eye.

• Iris: The colored portion of the eye; it is a smooth muscle that changes the size of the pupil to control the amount of light entering.

• Sclera: The white of the eye; it is a tough outer protective layer.

• Cornea: The glassy, transparent external surface of the eye that admits and refracts light.

• Optic Nerve: A bundle of axons from the retina that transmits external images to the brain.

• Eyelids: Structures that protect the eye from external damage.

• Eyelashes (Cilia): Protect the eye from foreign particles.

• Sebaceous Glands: Glands that secrete a lubricating oil onto the eyelashes.

• Conjunctiva: A mucous membrane that lines the inside of the eyelids and helps lubricate the eye by producing mucus and tears.

External Vision Apparatus and Muscle Conditions

• Lacrimal Apparatus: Responsible for producing and collecting tears to wash and lubricate the anterior surface of the eyeball.     * Superior and Inferior Lacrimal (Tear) Glands: Produce tears.     * Lacrimal Sac and Lacrimal Ducts: Collect tears.     * Nasolacrimal Duct: Drains tears into the nasal cavity.

• Strabismus: Eye muscle weakness resulting in the eyes looking in different directions at the same time.     * Esotropia (ST): A type of strabismus characterized by an inward turning of the eye; also referred to as cross-eyed.     * Exotropia (XT): A type of strabismus characterized by an outward turning of the eye; also referred to as wall-eyed.

Primary Layers and Internal Fluids of the Eye

• Eye Layers:     * Sclera: The outermost, tough protective layer.     * Choroid: The middle layer that supplies blood to eye structures. Its anterior portion consists of the iris, pupil, and ciliary body.     * Retina: The innermost layer containing sensory receptor cells known as photoreceptors.

• Internal Humors:     * Aqueous Humor: A watery fluid located in the anterior portion of the eye between the cornea and the lens.     * Vitreous Humor: A semi-solid gel located in the posterior chamber between the lens and the retina.

Physiology of Vision and Refraction

• Refraction: The bending of light waves as they enter a medium of a different speed. Light slows down at the air-cornea interface and within the aqueous humor.

• Refractive Power and Environment: Immersing the cornea in water eliminates its refractive power because light travels at similar speeds through water and aqueous humor. A scuba mask restores this power by maintaining an air interface.

• Accommodation: Changes in the shape of the lens to alter focal distance for near or far objects, controlled by the ciliary body muscles.

• Refractive Conditions:     * Emmetropia: A normal eye that focuses parallel light rays onto the retina without correction.     * Myopia (Nearsightedness): The cornea is too thick, causing light rays to converge before the retina; distant objects appear blurry.     * Hyperopia (Farsightedness): The cornea is too thin, focusing light behind the retina; near objects appear blurry.     * Astigmatism: Blurred vision caused by an uneven, oval-shaped cornea resulting in multiple focal points.     * Presbyopia: Visual loss due to old age, resulting in a decreased ability to focus on near objects.

• Path of Light: Cornea $\rightarrow$ Aqueous humor $\rightarrow$ Pupil $\rightarrow$ Lens $\rightarrow$ Vitreous humor $\rightarrow$ Retina.

Retinal Structure, Photoreceptors, and Color Vision

• Photoreceptors:     * Cones: Active in bright light; responsible for color vision.     * Rods: Active in dim light; responsible for seeing gray tones.

• Macula Lutea (Fovea Centralis): The part of the retina containing a very high concentration of cones; responsible for sharp, detailed central vision.

• Optic Disk: The point where the optic nerve leaves the eyeball. It contains no rods or cones, resulting in a physiological blind spot. Retinal blood vessels also enter and leave through this point.

• Color Vision Deficiencies:     * Achromatopsia: Complete color blindness; inability to perceive one or more colors.     * Monochromatism: Inability to perceive one specific color.     * Ishihara Test Examples:         * Normal vision sees "5" and "16".         * Red-green color blindness may see "2" or "45" or struggle to see the "16".         * Total color blindness results in seeing nothing in these test patterns.     * Types: Protanopia, Deuteranomaly, Tritanopia.

Clinical Eye Procedures, Professions, and Disorders

• Medical Professionals:     * Ophthalmologist: A medical doctor specialized in diagnosing and treating eye diseases.     * Ophthalmology: The branch of medicine involving eye diagnosis and treatment.     * Optometrist: A doctor of optometry who examines eyes, tests visual acuity, and prescribes lenses.     * Optometry: The medical profession specializing in examining visual acuity and prescribing corrective lenses.     * Optician: A person trained in grinding and fitting corrective lenses.

• Eye Disorders:     * Corneal Abrasion: A scraping injury to the cornea.     * Blepharoptosis: A drooping eyelid.     * Iridoplegia: Paralysis of the iris.     * Ophthalmalgia: Eye pain.     * Ophthalmoplegia: Paralysis of one or more extraocular muscles.     * Ophthalmorrhagia: Bleeding from the eye.     * Xerophthalmia: Dry eyes.     * Scleromalacia: Softening of the sclera.     * Photophobia: Strong sensitivity to bright light.     * Papilledema: Swelling of the optic disk, characterized by blurred disk margins.     * Cataract: Damage to the lens causing it to become cloudy.     * Glaucoma: Increased fluid pressure interfering with optic nerve function. Peripheral vision is lost first, leading to tunnel vision and potential blindness. Affects $20\%$ of adults over age $40$ and accounts for $15\%$ of blindness in America.     * Pterygium: Hypertrophied conjunctival tissue in the inner corner of the eye.     * Conjunctivitis (Pink Eye): Inflammation of the conjunctiva, usually due to bacterial infection.     * Hordeolum (Stye/Sty): A purulent infection of a sebaceous gland of the eyelid.     * Macular Degeneration: Deterioration of the macula lutea leading to central vision loss.     * Legally Blind: Defined as having $\text{20/200}$ acuity or worse.

Aural Combining Forms and Terminology

• acous/o, audi/o, audit/o: Hearing (e.g., acoustic, audio, auditory).

• aur/o, auricul/o: Ear (e.g., aural, auricular).

• cerumin/o: Cerumen/ear wax (e.g., ceruminal).

• cochle/o: Cochlea (e.g., cochlear).

• labyrinth/o: Labyrinth (e.g., labyrinthitis).

• myring/o: Tympanic membrane (e.g., myringitis).

• ot/o: Ear (e.g., otitis).

• salping/o: Eustachian tube (e.g., salpingitis).

• staped/o: Stapes (e.g., stapedial).

• tympan/o: Eardrum (e.g., tympanic).

• vestibul/o: Vestibule (e.g., vestibular).

Anatomy and Physiology of the Ear

• Main Divisions:     * External Ear: Consists of the Auricle (pinna) which captures sound waves and directs them through the external auditory meatus.     * Middle Ear: Transmits sound waves to the inner ear via the ossicles.     * Inner Ear: Contains sensory receptors for hearing and equilibrium.

• Specialized Structures:     * Cerumen: Ear wax produced by oil glands in the auditory canal to trap dirt.     * Tympanic Membrane (Eardrum): Vibrates when struck by sound waves.     * Ossicles: Malleus (hammer), Incus (anvil), and Stapes (stirrup). They amplify vibrations; the stapes transmits vibration to the Oval Window.     * Eustachian Tube: Connects the nasopharynx with the middle ear to equalize pressure with the atmosphere.     * Labyrinth: A cavity within the temporal bone housing inner ear organs.     * Cochlea: Responsible for sound processing (hearing). Movements at the oval window initiate fluid vibrations that bend the basilar membrane, stimulating hair cells.     * Semicircular Canals: Responsible for sensing angular or rotational acceleration.     * Otolith Organs (Utricle and Saccule): Responsible for sensing head tilt and linear acceleration.     * Vestibulocochlear Nerve (VIII): Transmits hearing and equilibrium information to the brain (pons).

Ear Medical Specialties and Equilibrium Testing

• Medical Specialties:     * Otology (Oto): The study of the ear.     * Audiology: The study of hearing disorders; the specialist is an audiologist.     * Otorhinolaryngology (ENT): The diagnosis and treatment of conditions of the ear, nose, and throat; the physician is an otorhinolaryngologist.

• Equilibrium Tests:     * Falling Test: Assessing balance by having a person stand on one foot with eyes open and then closed.     * Vestibular Oculomotor Reflex (VOR).     * Nystagmus: Jerky involuntary eye movements, often assessed during equilibrium tests.

Aural Pathology and Symptoms

• Hearing Loss Types:     * Conductive Hearing Loss: Caused by disease or malformation of the outer/middle ear; sounds are muffled as they are not conducted correctly.     * Sensorineural Hearing Loss: Caused by damage to the inner ear (cochlea) or the cochlear nerve.

• Aural Symptoms:     * Residual Hearing: The amount of hearing remaining after damage.     * Tinnitus: Ringing in the ears.     * Vertigo: Dizziness.

• Conditions:     * Otitis Externa (OE): External ear infection, often fungal (otomycosis), also called swimmer's ear.     * Otosclerosis: Loss of mobility of the stapes bone due to bone growth, leading to hearing loss.     * Otitis Media (OM): Infection of the middle ear, common in children. Can be watery (serous otitis media) or pus-filled (purulent otitis media).     * Acoustic Neuroma: A benign tumor of the cochlear nerve causing tinnitus, headache, dizziness, and hearing loss.

• Clinical Tools and Devices:     * Otoscope: Instrument used to visually examine the ear canal and eardrum.     * Tympanometry: Measurement of tympanic membrane movement to assess middle ear pressure.     * Cochlear Implant: A mechanical device surgically placed behind the ear to convert sound into magnetic impulses, stimulating the auditory nerve to treat sensorineural hearing loss.

• Hearing Aids: Devices that amplify sound for individuals with hearing loss, fitting inside or behind the ear to improve auditory perception.

Diagnostic Imaging

• Radiology Fundamentals:     * Radiolucent: Materials/tissues that allow X-rays to pass through.     * Radiopaque: Materials/tissues that do not allow X-rays to pass through.

• Advanced Imaging Techniques:     * Positron Emission Tomography (PET): Produced by injecting radioactive glucose. Glucose accumulates in areas of high metabolic activity (e.g., brain, tumors), allowing for comparison of activity, such as between normal and Alzheimer's disease-affected brains.     * Functional Magnetic Resonance Imaging (fMRI): Measures brain activity by detecting associated changes in blood flow. Limitations include loud scanner noise (distracting for auditory studies) and signal distortion caused by small mouth movements/speaking.