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Astigmatism
Overview
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Astigmatism
means that the cornea is oval like a football instead
of spherical like a basketball. Most astigmatic
corneas have two curves ¨C a steeper curve and a
flatter curve. This causes light to focus on more
than one point in the eye,resulting in blurred vision
at distance or near. Astigmatism often occurs along
with nearsightedness or farsightedness.
What
is a cataract |
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| When cataracts are mentioned, people
often think of a film that grows on their eyes causing
them to see double or blurred images. However, a cataract
does not form on the eye, but rather within the eye. |
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| A cataract is a clouding
of the natural lens, the part of the eye responsible
for focusing light and producing clear, sharp images.
The lens is contained in a sealed bag or capsule.
As old cells die they become trapped within the
capsule. Over time, the cells accumulate causing
the lens to cloud, making images look blurred or
fuzzy. For most people, cataracts are a natural
result of aging.In fact, they are the leading cause
of visual loss among adults 55 and older. Eye injuries,
certain medications, and diseases such as diabetes
and alcoholism have also been known to cause cataracts. |
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Glaucoma
Glaucoma is a disease caused by increased intraocular
pressure (IOP) resulting either from a malformation or
malfunction of the eye¡¯s drainage structures. Left untreated,
an elevated IOP causes irreversible damage the optic nerve
and retinal fibers resulting in a progressive, permanent
loss of vision. However, early detection and treatment
can slow, or even halt the progression of the disease.
The above photos show progressive
optic nerve damage (indicated by the cup to disc ratio)
caused by glaucoma. Notice the pale appearance of the
nerve with the 0.9 cup as compared to the nerve with the
0.3 cup.
Farsightedness
(Hyperopia)
Farsightedness or hyperopia, occurs when light entering
the eye focuses behind the retina, instead of directly
on it. This is caused by a cornea that is flatter,
or an eye that is shorter, than a normal eye. Farsighted
people usually have trouble seeing up close, but
may also have difficulty seeing far away as well.
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| Young people with mild to moderate
hyperopia are often able to see clearly because
their natural lens can adjust, or accommodate to
increase the eye¡¯s focusing ability. However, as
the eye gradually loses the ability to accommodate
(beginning at about 40 years of age), blurred vision
from hyperopia often becomes more apparent. |
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Nearsightedness
(Myopia)
Nearsightedness or myopia, occurs when light entering
the eye focuses in front of the retina instead of directly
on it. This is caused by a cornea that is steeper, or
an eye that is longer, than a normal eye. Nearsighted
people typically see well up close, but have difficulty
seeing far away.
This problem is often discovered in school-age children
who report having trouble seeing the chalkboard. Near-sightedness
usually becomes progressively worse through adolescence
and stabilizes in early adulthood. It is an inherited
problem.
Presbyopia
Presbyopia, also known as the ¡°short arm syndrome,¡± is
a term used to describe an eye in which the natural lens
can no longer accommodate. Accommodation is the eye¡¯s
way of changing its focusing distance: the lens thickens,
increasing its ability to focus close-up. At about the
age of 40, the lens becomes less flexible and accommodation
is gradually lost. It¡¯s a normal process that everyone
eventually experiences.
Most people first notice difficulty reading very fine
print such as the phone book, a medicine bottle, or the
stock market page. Print seems to have less contrast and
the eyes become easily fatigued when reading a book or
computer screen. Early on, holding reading material further
away helps for many patients. But eventually, reading
correction in the form of reading glasses, bifocals, or
contact lenses is needed for close work. However, nearsighted
people can simply take their glasses off because they
see best close-up.
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