Ophthalmology: Eye Word Parts

• The Latin word opticus means "of sight or seeing".
• The suffixes -opia and -opsia both mean "vision".
• Many word parts refer to specific structures within the eye.

Eye Word Parts

• blepharo: eyelid
• conjunctiv/o: conjunctiva (conjunctivae, plural)
• corne/o: cornea
• dacry/o: tears, lacrimal sac, or lacrimal duct
• diplo: two, double
• irid/o: iris
• kerat/o: hard, cornea
• lacrim/o: tear, lacrimal apparatus
• ocul/o: eye
• ophthalm/o: eye
• -opia: vision
• opt/o: light, eye, vision
• phac/o: lens
• presby/o: old age
• pupil/o: pupil
• retin/o: retina
• scler/o: relating to the sclera, hard
• uve/o: denoting the pigmented middle eye layer

Structure and Function of the Eye

• Eyes take continuous pictures and transmit them to the brain, which converts them to images in motion.
• The eye is within the orbit, a bony cavity formed by seven bones of the skull.
• Accessory structures of the eyes include the extraocular muscles, eyebrows, eyelids, eyelashes, conjunctiva, and lacrimal apparatus.
• Extraocular muscles are muscles within the orbit but outside the eyeball that move the eyes.
• Eyebrows are the crescent-shaped line of hairs on the superior edge of the orbit.
• Movable upper and lower folds that cover the surface of the eyeballs when they close are called eyelids (palpebrae).
• Stiff hairs projecting from the eyelid margins are eyelashes.
• The angle formed by the junction of the lateral parts of the upper and lower eyelids is known as the lateral angle of eye (lateral canthus).
• The medial angle formed by their union is the medial angle of eye (medial canthus).
• The conjunctiva is the mucous membrane that lines the anterior surface of the eyeball and the underside of the eyelid; it covers and protects the exposed surface of the eyeball.
• The lacrimal apparatus consists of structures associated with tear production and flow.
• Lacrimal glands, located superior to the outer corner of each eye, secrete tears to cleanse and moisten the eyeball surface.
• The lacrimal sac stores tears.
• Lacrimal ducts are channels that carry tears to the eyes.
• Nasolacrimal ducts carry tears from the lacrimal glands to the nose.
• The eyeball has three layers: fibrous layer, vascular layer, and inner layer.
• The fibrous layer consists of the sclera and cornea.
• The vascular layer (uvea) consists of the choroid, ciliary body, and iris.
• The inner layer has the retina and optic nerve.
• The sclera, also known as the white of the eye, helps maintain the shape of eyeball.
• The cornea is the transparent portion that provides most of the optical power of the eye by bending light rays to focus on the retina.
• The choroid is the opaque layer of the eyeball that contains vessels that supply blood to the eye.
• The ciliary body is a thickened portion between the choroid and iris.
• Its muscles suspend the lens and adjust light entering the eye.
• The lens is a transparent structure posterior to the pupil that bends and focuses light rays on the retina.
• It is held in place by the ligaments of the ciliary body.
• The ciliary muscles control the shape of the lens to allow for far and near vision.
• The iris is the pigmented muscular ring that surrounds and controls the size of the pupil, which is the opening in the middle of the iris through which light enters.
• The retina is the innermost layer of the eye that contains visual receptors (rod and cones).
• The optic nerve carries nerve impulses from the retina to the brain to give us the sense of sight.
• The interior spaces (chambers) of the eyeball contain fluid.
• The anterior chamber is the space between the cornea and the lens, filled with aqueous humor.
• The posterior chamber is the space between the lens and retina that contains vitreous humor.
• Photoreceptors are the specialized visual receptor cells in the retina.
• Rods are black and white receptors that respond to dim light.
• Cones are color receptors that provide color vision and sharp vision (visual acuity).
• Photosensitive cells receive light waves through the cornea and convert them into nerve impulses.
• Nerve impulses are carried to the brain through the optic nerve.
• The macula is an oval area of the retina, and its center is a pit called the fovea centralis.
• Fovea centralis is saturated with cones and permits the best possible color vision.
• The optic disc is the location where nerve fibers from the retina converge to form the optic nerve and is referred to as the blind spot because it has no photoreceptors.
• Refraction, the bending of light rays, is the ability of the eye to change the direction of light in order to focus it on the retina.
• Light rays are refracted by the cornea and lens to focus an image on the retina.
• Accommodation is the automatic adjustment of focusing the eye by flattening or thickening the lens.

Disorders Related to the Eye

• Refractive errors, infections, and disorders of the eyelids are common eye disorders.
• Refractive errors can be corrected with glasses, contact lenses, or operations that reshape the cornea.
• Other eye conditions can be treated with medications or surgery.

Refractive Errors

• Hyperopia is farsightedness, where the image falls behind the retina, making it difficult to see close objects clearly.
• Myopia is nearsightedness, where the image falls in front of the retina, making it difficult to see distant objects clearly.
• Presbyopia is farsightedness caused by aging.
• Astigmatism means the light coming into the eye does not focus on a single point; the condition is caused by an irregularity of the curve of the cornea or lens that distorts light entering the eye.
• Corrective lenses can usually compensate for any refractive error.

Infections

• Conjunctivitis, or pinkeye, is an inflammation of the conjunctiva that causes small blood vessels to become more prominent, giving the sclera a pink or red color.
• Keratitis is an inflammation of the cornea when the cornea has been scratched or otherwise damaged.
• Dacryocystitis is an inflamed lacrimal sac.

Disorders of the Eyelids

• Blepharoptosis is drooping of the upper eyelid.
• Ectropion is a condition in which the eyelid is turned outward away from the eyeball.
• Entropion is a condition that causes the eyelid to roll inward against the eyeball.
• A hordeolum, commonly called a sty, is an infection of the oil gland of an eyelash.

Other Disorders of the Eye

• Xerophthalmia, also known as dry eyes, occurs when the surface of the eye becomes dry.
• Glaucoma is a disease characterized by an increase in intraocular pressure that causes damage to the optic nerve.
• Cataract means cloudiness or opacity of the lens.
• It may be caused by disease, injury, chemicals, or exposure to various physical elements.
• Surgery to replace with an artificial intraocular lens is a common treatment.
• An ophthalmoscope is the instrument by which practitioners can examine the interior of the eye by looking through the pupil.
• Laser-assisted in situ keratomileusis (LASIK) is a procedure used to correct vision problems by using a laser to create a corneal flap and reshape the cornea.
• Treatment for a detached retina or retinal tear may include scleral buckling, where a silicone band is attached to the scleral peripheral behind the eye, pulling the retina together.

Practice and Practitioners of the Eye

• An ophthalmologist provides eye care ranging from prescribing corrective lenses to performing surgery; this requires completing an undergraduate degree, a doctorate in medicine, a 1-year internship, and 3 or more additional years of specialized clinical training in ophthalmology.
• Optometry is the profession concerned with examination of the eyes and related structures.
• An optometrist is a doctor of optometry who examines eyes and prescribes corrective lenses; a preprofessional undergraduate education plus 4 years of professional education at an accredited college of optometry are required to become an optometrist.
• An optician fills eyeglass prescriptions and dispenses eyewear; a high school diploma and successful completion of an accredited optician program (1 year of study) are required to become an optician.

Ear Word Parts

• acous/o, acus/o, acoust/o: hearing
• audi/o: sound
• aur/o: ear
• auricul/o: ear
• myring/o: tympanic membrane (eardrum)
• ot/o: ear
• staped/o: stapes (smallest ear bone)
• tympan/o: eardrum

Structure and Function of the Ear

• The ear is an organ of hearing and equilibrium: it is divided into the external ear, middle ear, and internal ear.
• The external ear consists of the auricle (outer ear), external acoustic meatus (passageway), and tympanic membrane (eardrum).
• It directs sound waves into the ear.
• Ceruminous glands line the external acoustic meatus and secrete cerumen to protect the ear by preventing dust, insects, and some bacteria from entering the middle ear.
• The middle ear consists of the tympanic cavity with its auditory ossicles (bones), associated muscles, and the auditory tube.
• The internal ear contains the vestibule, bony labyrinth of semicircular canals and the cochlea.
• Sound waves entering the ear vibrate the eardrum/tympanic membrane.
• A tiny tympanic cavity in the skull houses the auditory ossicles, three small bones called the malleus, incus, and stapes, which are also sometimes referred to as the hammer, anvil, and stirrup because of their shapes.
• Sound waves affect these tiny bones and cause them to transmit sound vibrations to the internal ear.
• The auditory tube reaches from the tympanic cavity to the nasopharynx to help equalize pressure in the ear with outside atmospheric pressure.
• The internal ear has a bony labyrinth (maze) that contains the sensory receptors for hearing and balance.
• Major structures of the bony labyrinth include the semicircular canals (organ of balance) and cochlea (organ of hearing).
• Receptors in the cochlea change sound waves into nerve impulses that the brain can process.

Disorders Related to the Ear

• Ear disorders can occur in any part of the ear.
• Impacted cerumen is an accumulation of earwax in the external acoustic meatus, may cause hearing loss.
• Otalgia or otodynia is an earache caused by trauma or infection.
• Otitis is any inflammation of the ear.
  • Otitis externa: inflammation of the outer ear
  • Otitis media (OM): inflammation of the middle ear
  • Otitis interna: inflammation of the inner ear
• Otitis media is the most common type of ear inflammation.
• Hearing loss ranges from a partial loss of frequencies to complete deafness.
• Conductive hearing loss: sound waves are not conducted through the external ear to the ossicles of the middle ear.
• Sensorineural hearing loss: damage to the cochlea of the internal ear or to the nerve pathways to the brain.
• Presbycusis is a progressive hearing loss that occurs with aging.
• Anacusis is total deafness.
• Myringitis: inflammation of the tympanic membrane.
• Mastoiditis: inflammation of the mastoid air cells.
• Labyrinthitis: an inflammation of the labyrinth.
• Otosclerosis: hardening of the stapes, resulting in sound being unable to travel from the outer ear to the internal ear.
• Ménière's syndrome is a chronic disease of the internal ear characterized by vertigo, tinnitus, and periodic hearing loss.
• Vertigo is dizziness and/or a loss of balance.
• Tinnitus is a ringing, buzzing, or roaring sound in the ears.

Diagnostic Tests, Treatments, and Surgical Procedures of the Ear

• Disorders of the ear are treated by surgical intervention, including:
  • Otoplasty: surgical repair of the auricle of the ear
  • Mastoidectomy: surgical removal of the mastoid process of the temporal bone
  • Myringectomy or tympanectomy: surgical removal of all or part of the tympanic membrane
  • Myringotomy: surgical incision of the eardrum to create an opening for placement of drainage tubes
  • Tympanoplasty: surgical correction of a damaged tympanic membrane
  • Stapedectomy: surgical removal of the stapes
  • Labyrinthotomy: a surgical incision into the labyrinth.

Practice and Practitioners of the Ear

• Audiology is the specialty dealing with hearing and hearing disorders.
• An audiologist measures hearing and treats hearing impairments.
• An otoscope is an instrument with light and lenses used to visually examine the external ear and eardrum.
• Otology is the study of the ear and its related structures.
• An otologist diagnoses and treats diseases of the ear and its related structures.
• An otorhinolaryngologist specializes in the diagnosis and treatment of diseases that involve the ear, nose, and throat.

Abbreviations

• AD: right ear.
• AS: left ear.
• AU: both ears.
• EXOM: extraocular movements.
• IOP: intraocular pressure.
• LASIK: laser-assisted in situ keratomileusis.
• OD: right eye.
• O.D.: doctor of optometry.
• OM: otitis media.
• OS: left eye.
• OU: both eyes.