Download Key Medical Terms Associated with the Eye and Ear

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Key Medical Terms Associated with the Eye and Ear
Strabismus vs. Amblyopia
Strabismus: Misalignment of the eyes so that the eyes do not move in unison when viewing
an object; the affected eye turns either medially or laterally with respect to the normal eye and the
result is double vision (diplopia). It can be caused by abnormal innervation, problems with the extra
ocular muscles, physical trauma, or a central processing problem. Cross-eye (esotropia) involves one
eye looking at an object and the other turning inward. In walleye (exotropia), the deviated eye turns
outward. Children with strabismus can develop to a point that the brain subconsciously suppresses
the image arising from the deviating eye; eventually, this eye becomes amblyopic (“lazy”) that the
child can become blind in that eye.
Amblyopia (commonly called lazy eye): With amblyopia, there is no apparent damage or
abnormality to the eye, it is a developmental disorder of the brain where the part of brain receiving
signals from the affected eye does not develop properly as it does not get stimulated to its full
potential during the critical period. The critical period is the time duration from birth to two years in
humans, where the visual cortex of the brain develops due to the magnitude of visual information it
receives. Eventually, the brain may ignore the signals received from the weaker — or lazy — eye and
the brain "turns off" the visual processing of one eye to prevent double-vision, for example in
strabismus (crossed eyes). Conservative treatments such as corrective eye wear or eye patches can
often correct lazy eye. Sometimes, lazy eye requires surgical treatment.
Conjunctivitis (pinkeye): An inflammation of the conjunctiva; when caused by bacteria such as
pneumococci, staphylococci, or Hemaophilus influenza, it is very contagious and more common in
children. Conjunctivitis may also be caused by irritants, such as dust, smoke, or pollutants in the air,
in which case it is not contagious.
Corneal transplant: A procedure in which a defective cornea is removed and a donor cornea of
similar diameter is sewn in. It is the most common and most successful transplant operation. Since
the cornea is avascular, antibodies in the blood that might cause rejection do not enter the
transplanted tissue and rejection rarely occurs.
Diabetic retinopathy: Degenerative disease of the retina due to diabetes mellitus, in which blood
vessels in the retina are damaged or new ones grow and interfere with vision.
Nystagmus: A rapid involuntary movements of the eyes. The involuntary eye movements of
nystagmus are caused by abnormal function in the areas of the brain that control eye movements.
The part of the inner ear that senses movement and position (the labyrinth) helps control eye
movements. The exact nature of this disorder is poorly understood. There are two forms of
nystagmus: Congenital nystagmus is present at birth. Acquired nystagmus can result from inner ear
disorders such as labyrinthitis However, the most common cause is probably toxic -- certain drugs or
medication, including Dilantin (an antiseizure medication), alcohol intoxication, or any sedating
medicines can harm the labyrinth. In young people, a common, serious cause of acquired nystagmus
is head injury from motor vehicle accidents. In older people, a common, serious cause is stroke
(blood vessel blockage in the brain). Any disease of the brain (such as multiple sclerosis or brain
tumors) can cause nystagmus if the areas controlling eye movements are damaged.
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Ptosis (TO-sis): Falling or drooping of the eyelid (or slippage of any organ below its normal position).
Tinnitus: A ringing, roaring, or clicking in the ears. Tinnitus isn't a condition itself — it's a symptom of
an underlying condition, such as age-related hearing loss, ear injury or a circulatory system disorder.
Although bothersome, tinnitus usually isn't a sign of something serious. A number of health conditions
can cause or worsen tinnitus. In many cases, an exact cause is never found. A common cause of
tinnitus is inner ear cell damage. Tiny, delicate hairs in your inner ear move in relation to the pressure
of sound waves. This triggers ear cells to release an electrical signal through a nerve from your ear
(auditory nerve) to your brain. Your brain interprets these signals as sound. If the hairs inside your
inner ear are bent or broken, they can "leak" random electrical impulses to your brain, causing
tinnitus. Other common causes include age-related hearing loss and exposure to loud noise. Loud
noises, such as those from heavy equipment, chain saws and firearms, are common sources of
noise-related hearing loss. Portable music devices, such as MP3 players or iPods, also can cause
noise-related hearing loss if played loudly for long periods. Tinnitus caused by short-term exposure,
such as attending a loud concert, usually goes away; long-term exposure to loud sound can cause
permanent damage. Certain medications in high doses can cause tinnitus. Often the unwanted noise
disappears when you stop using these drugs. Medications known to cause or worsen tinnitus include:
Antibiotics (including chloramphenicol, erythromycin, gentamicin, vancomycin and bleomycin) ,
diuretics, quinine medications used for malaria or other health conditions and aspirin taken in
uncommonly high doses (12 or more a day).
Keratitis: An inflammation or infection of the cornea.
Trachoma: A serious form of conjuntivitis and the greatest single preventable cause of blindness in
the world. It is caused by the bacterium Chlamydia trachomatis. The disease produces an excessive
growth of subconjunctival tissue and invasion of blood vessels into the cornea, which progresses until
the cornea is opaque. Antibiotics can prevent long-term complications if used early in the infection. In
certain cases, eyelid surgery may be needed to prevent long-term scarring, which can lead to
blindness if not corrected. Early treatment before the development of scarring and lid deformities has
an excellent prognosis.
Vertigo: A sensation of spinning or movement in which the world seems to revolve or the person
seems to revolve in space. Often associated with nausea and, in some cases, vomiting. It may be
caused by arthritis of the neck or an infection of the vestibular apparatus.