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This is a 'mini-glossary' of eyecare terminology. It is intended
for informational use only, and not for use in self-diagnosis and
treatment. If you have an eye or vision problem, we strongly encourage
you see your eyecare specialist. This information has been provided
by the Indiana University
School of Optometry.
Eye and Vision Terminology
Amblyopia (lazy eye)
Amblyopia, more commonly known as lazy eye, is a lack of development
of vision in an eye that is not due to any obvious eye or vision
problem such as myopia or eye disease. The exact cause of amblyopia
is not known, but is often due to crossed or wandering eye (strabismus),
or to a significant difference in the size or optics of the two
eyes. Amblyopic eyes are not blind, but central vision is severely
reduced. Amblyopia can usually be treated successfully with a program
of eye patching and visual training. Because of the detrimental
effects of amblyopia on school and job performance, and because
children with amblyopia usually are not aware of a problem, early
detection and treatment through comprehensive examination by an
eyecare specialist is very important.
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Astigmatism
Astigmatism is caused by an irregularity in the shape of the cornea,
the clear front surface of the eye. Normally, the cornea has a regular,
spherical shape, much like that of a basketball. In an astigmatic
eye, the cornea is more oval or elliptical in shape, like the side
of a football. Since the cornea is involved in focusing light as
it enters the eye, this distortion in shape leads to a blurred image
being formed on the retina of the eye. Astigmatism is not a disease,
but an optical problem of the eye, and is treated with the use of
glasses or contact lenses. Symptoms of astigmatism include blurry
vision of objects both far away and up close, headaches, eyestrain
and eye fatigue.
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Cataracts
Cataracts result when the normally clear lens within the eye becomes
cloudy and opaque. Thus, a cataract occurs inside the eye and not
on the outside. Cataracts usually affect people over the age of
60, but they can also be found in younger people, including infants
and children. The cause of cataract is not known, but seems to be
related to such factors as eye injury, eye diseases like diabetes,
various drugs and medications, excessive exposure to ultraviolet
radiation present in sunlight, and the normal aging process. There
is no proven method currently available to prevent cataracts, and
surgery is the only way to effectively treat cataracts. The surgical
procedure is relatively uncomplicated and has a success rate of
well over 90 percent. A comprehensive eye examination given by your
eyecare professional can determine if you have a cataract forming.
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Conjunctivitis
Conjunctivitis is an inflammation of the conjunctiva, the thin,
clear membrane that covers the outside of the eye. Conjunctivitis
can be caused by a variety of things like allergies, infections
due to bacteria or virus, contact lenses and chemical irritation.
"Pinkeye" is a particularly contagious form of conjunctivitis,
often found in children and young adults. Chlamydia, a type of sexually
transmitted disease, can also cause conjunctivitis in sexually active
individuals. Symptoms of conjunctivitis can include red and watery
eyes, red and irritated eyelids, blurry vision and a sandy, scratchy
feeling in the eyes. A person with these symptoms should be evaluated
promptly by an eyecare specialist. Many forms of conjunctivitis
can be effectively treated with eyedrops or other forms of therapy.
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Diabetes and the Eye
Diabetes is a disease characterized by an inability of the body
to produce or use insulin, a chemical that helps break down sugar
in the blood. Diabetes can affect many parts of the body, including
the eyes. In fact, diabetic eye disease is one of the leading causes
of blindness in the U.S. This disease can cause changes in farsightedness
and nearsightedness and it can cause cataracts and glaucoma. But
the most serious and devastating problem that is caused by diabetes
is called diabetic retinopathy. Diabetic retinopathy occurs when
there is a weakening of the tiny blood vessels that feed the retina,
the thin, fragile membrane that covers the back of the eye and contains
the sensitive photoreceptors called the rods and cones.
Left untreated, diabetic retinopathy can and will lead to blindness.
In order to reduce the risk of diabetic eye disease, two things
are necessary. First of all, once diabetes is diagnosed, regular
examinations by a physician are needed to monitor the condition.
Diabetes must be controlled as much as possible and the key to control
is to follow the advice of a physician. Second, regular eye and
vision evaluations, including a complete examination of the retinas
of the eyes, are essential.
Diabetic eye disease can often be successfully treated with lasers
or surgery, but early detection is crucial.
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Glaucoma
Glaucoma is actually a family of eye diseases characterized by excessive
pressure of the fluid within the eye which damages the delicate
optic nerve causing a loss of vision. Glaucoma is often called "the
sneak thief of sight" because visual loss usually goes unnoticed
by the patient in the early stages of the disease. The cause of
glaucoma is not known, but seems to be related to a blockage of
aqueous fluid drainage channels. The most common form of glaucoma
is called primary open-angle glaucoma and there does seem to be
a hereditary factor. Other forms of glaucoma can result from eye
injuries or diseases such as diabetes. Because glaucoma has no symptoms
in early stages, a comprehensive eye examination by an eyecare professional
is essential for prompt diagnosis. Treatment usually begins with
eye drops, but in advanced stages, surgery may be necessary.
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Hyperopia (farsightedness)
Hyperopia, or farsightedness, is a vision problem where objects
far away are usually seen clearly but objects close to the eye are
not properly focused which can lead to blurriness and eyestrain
when doing nearpoint tasks such as reading or sewing. Hyperopia
typically occurs when the eyeball is too short or the cornea of
the eye is not curved enough. Glasses or contact lenses will correct
this problem by properly focusing near objects. Because of the detrimental
effects of farsightedness on near work such as reading, proper visual
diagnosis and treatment is especially important for those who use
their eyes extensively in close work, like students (of all ages),
CRT operators, and secretaries.
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Hypertension and the Eye
Hypertension, or high blood pressure, is a disease that can have
serious effects on many parts of the body, including the eyes. Eye
disease due to hypertension is due to damage to the tiny blood vessels
that feed the retina, the thin, fragile membrane that covers the
back of the eye and contains the sensitive photoreceptors called
the rods and cones. In order to reduce the risk of hypertensive
eye disease, two things are necessary. First of all, once hypertension
is diagnosed, regular examinations by a physician are needed to
monitor the condition. Hypertension must be controlled as much as
possible and the key to control is to follow the advice of a physician.
Second, regular eye and vision evaluations, including a complete
examination of the retinas of the eyes, are essential.
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Macular Degeneration
The retina of the eye is a thin, fragile membrane that covers the
inside surface of the back of the eye and contains the sensitive
photoreceptors called rods and cones. The macula is the area of
retina that is responsible for central vision. It is the part of
the retina that is used when viewing objects straight ahead. Macular
degeneration is a disease that causes damage to the macula during
the aging process, possibly leading to severe vision loss. The actual
cause of macular degeneration is not known, but factors such as
heredity, nutrition, hypertension, smoking and long term excessive
exposure to ultraviolet radiation from the sun may be linked to
the disease. There are two different types of macular degeneration,
and many cases can be successfully treated with lasers, especially
if detected early.
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Myopia (nearsightedness)
Myopia, or nearsightedness, is a visual problem where objects close
to the eye are seen clearly but objects far away are not properly
focused and therefore appear blurry. Myopia typically occurs when
the eyeball is too long or the cornea of the eye has too much curvature.
Genetics and heredity seem to be major determining factors in the
development of myopia. Glasses or contact lenses will correct this
problem by properly focusing distant objects. Myopia often begins
early in childhood, sometimes as early as 5 years of age. Thus,
children should have their first complete eye and vision examination
before they begin school, as it is common for young children NOT
to complain of blurry vision despite being nearsighted.
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Ophthalmologist
Ophthalmologists are physicians who have graduated from medical
school and have spent several years in internship, residency and
possibly fellowship obtaining additional skills and training. Ophthalmologists
are specialists in the surgical treatment of eye disease, and as
such play a vital role on the eyecare team. While an optometrist
may be considered to be a primary care provider, that is to say
the first professional a patient may see for an eye or vision problem,
the ophthalmologist's role may be that of a secondary or tertiary
care provider. Because of their intensive and highly specialized
training, ophthalmologists may see advanced cases of eye disease
or those requiring surgical treatment, referred from the primary
care providers, including the optometrist.
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Optometrist
Doctors of Optometry, or optometrists, like physicians and dentists,
are primary health care providers. Optometrists are the principal
providers of eye and vision care in the United States. They are
responsible for diagnosing and treating not only optical problems
with the eye's focusing system, but also the commonly occurring
eye diseases and abnormalities that affect the general population.
Spectacles, contact lenses, visual training and medications are
all routine tools with which optometrists treat their patients.
As members of the health care team, optometrists work closely with
other professionals such as internists, general practitioners, neurologists,
and eye surgeons. This teamwork is important - many systemic diseases
may reveal themselves as changes within the eye's tissues.
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Presbyopia
Presbyopia results from an inability of the eye to change focus
from distant objects to near objects. Normally, the crystalline
lens, which is located inside of the eye, changes shape during the
focusing process, allowing objects to be seen clearly at all distances.
During the normal aging process, the crystalline lens gradually
hardens and becomes more resistant to changes in shape, thus fixing
the eye's focus on distant objects. This process usually begins
at about 40 years of age and may continue for 15 to 20 years, after
which time no change in lens shape is possible. The usual treatment
for this condition is a bifocal or trifocal spectacle lens which
provides more than one lens power to focus on objects at more than
one distance.
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Retinal Detachment
The retina of the eye is a thin, fragile membrane that covers the
inside surface of the back of the eye and contains the sensitive
photoreceptors called rods and cones. Normally, the retina is well
protected from damage by the fluid that fills the eye, called the
vitreous fluid, and by the strong skull bones that surround the
eye. However, because the retina is so thin and fragile, it is vulnerable
to damage such as holes and tears. This damage can occur as a result
of an eye or head injury (for example, in boxing), but it can also
occur for other reasons such as a family predisposition to retinal
disease or very high amounts of nearsightedness, which can stretch
the retina. These problems can lead to a condition called retinal
detachment.
Retinal detachment is a separation of the retina from the outer
layers of the eye. This detachment may only involve a small part
of the retina at first, but can quickly increase in size, eventually
involving the entire retina, and resulting in severe vision loss.
Regular eye examinations can identify risk factors which may lead
to a retinal detachment. Also, a retinal detachment may cause symptoms
such as floaters (small, black spots in a person's vision), or bright
flashes of light seen in the periphery of a person's vision. It
is important to realize that most cases of floaters in vision are
normal, and not a symptom of retinal detachment; however, any significant
change in a person's vision should be evaluated promptly by an eye
care specialist. If detected early, retinal holes, tears and detachments
can often be successfully treated with lasers or surgery.
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Strabismus
Strabismus, which is also referred to as crossed-eyes, is a condition
where the two eyes are not properly aligned. As a result one of
the eyes may be turned in or out, or even up or down. Normally,
the two eyes are designed to work together as a team, especially
to improve depth perception and increase peripheral vision. This
eye teamwork is significantly impaired by the misalignment of strabismus.
Strabismus also frequently leads to a condition called amblyopia,
or lazy eye. Strabismus can usually be treated successfully with
a program of eye patching and visual training. Because of the detrimental
effects of strabismus on school and job performance, early detection
and treatment through comprehensive examination by an eyecare specialist
is very important.
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Vision Therapy
Vision therapy is an eye and vision treatment program that can be
effective in certain cases of amblyopia (lazy eye), strabismus (crossed-eyes),
and visual-perceptual problems. This therapy is designed to improve
eye movement skills, focusing, eye coordination and eye teamwork.
An eyecare specialist will prescribe specific visual tasks, which
are designed to be practiced and repeated regularly under controlled
conditions. The duration of visual therapy ranges from a few weeks
to several months depending upon the severity of the vision problem,
patient motivation and the degree of visual improvement desired.
The effectiveness of such therapy also depends upon similar factors.
A complete eye and vision examination will indicate whether or not
a person may benefit from a vision training program.
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