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Refractive
Errors
To
see clearly, light rays must be bent or refracted to focus
on the retina, the light- sensitive nerve layer that lines
the back of the eye. The cornea and lens of the eye work
together to bend or refract light rays and bring them together
on the retina. If a refractive error is present, the light
is not focused directly on the retina, so images appear
blurry.
Myopia
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Myopia
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After Lasik Surgery for Myopia
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Myopia
(nearsightedness): Distance vision is impaired when
the eye is too long in relation to the curvature of
the cornea. This causes light to focus before it reaches
the retina. Close objects look clear but distant objects
appear blurry. |
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Myopic Vision
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Hyperopia
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Hyperopia
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After Lasik Surgery for Hyperopia
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Hyperopia
(farsightedness): Close vision is impaired, with some
impairment of distance vision, as well. The eye is too
short in relation to the curvature of the cornea. Light
rays are not yet in focus when they reach the retina,
so images appear blurry. |
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Hyperopic Vision
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Astigmatism
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Astigmatism
(the cornea is oval shaped instead of round): The irregular
curvature of the cornea causes light to focus on more
than one point on the retina. Uncorrected astigmatism
impairs both distance and near vision. |
Presbyopia
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Presbyopia
(aging eyes): When young, the lens of the eye is soft
and flexible, allowing people to see objects both close
and far away. After the age of 40, the lens of the eye
becomes more rigid, making it more difficult for the
lens to change its shape, or accommodate, to do close
work such as reading. This condition is known as presbyopia
and is the reason reading glasses or bifocals are necessary
at some point after age forty. |
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Presbyopic Vision
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UNDERSTANDING
YOUR GLASSES PRESCIPTION
Your
glasses prescription is written with three numbers. If your
prescription reads -3.00-0.50 x 065, this means you are
nearsighted with a small amount of astigmatism.
The
first number (-3.00) identifies your degree of nearsightedness
or farsightedness. The - sign means you are nearsighted
and the + sign means you are farsighted.
The
second number (-0.50) identifies your degree of astigmatism.
The number can be written either with a + sign or a - sign.
The
third number (065) is the axis, which indicates the direction
of your astigmatism.
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