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Glossary
Astigmatism
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Astigmatism is blurry vision produced by football-shaped cornea
that is too steep in one place and too flat in another. Astigmatic
corneas focus light in two different places in the eye, making
both near and distance vision a problem.
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Best corrected visual acuity (BCVA)
- The
best possible vision a person can achieve with corrective lenses
measured in terms of Snellen lines on an eye chart.
- Cornea
- The
cornea is sometimes referred to as the 'window of the eye.' It
provides most of the focusing power when light enters the eye. The
cornea is composed of five layers of tissue. This is the part of
the eye reshaped by laser vision correction.
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Epithelium
- The
outer layer of the cornea that serves as the eye's protective
layer.
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Pupil
- The
pupil is the "black circle" in your eye. The primary function of
the pupil is to control the amount of light entering your eye.
When you are in a bright environment, the pupil becomes smaller to
allow less light to pass through. When it is dark, the pupil
expands to allow more light to reach the back of your eye.
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Lid Speculum
- An
instrument, placed in the eye before surgery, to gently hold the
lids apart, eliminating possibility of blinking.
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Lower-Order Aberrations
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Also called refractive errors; includes myopia, hyperopia and
astigmatism.
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Presbyopia
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Presbyopia develops as the lens of the eye loses some of the
flexibility that characterizes a younger eye. Everyone experiences
the effects of presbyopia, typically between the ages of 40 and
50.Back
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Nearsightedness (Myopia)
- A
refractive error in which you see better close up than from a
distance. Myopia is caused by an eyeball that is too long to focus
light on the retina or a cornea which is too steeply curved.
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- Diopter
- A
measurement of the degree to which light converges or diverges;
also a measurement of lens refractive power.
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- Custom
LASIK
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CustomLASIK is a procedure that enables your surgeon to further
customize the conventional LASIK procedure to your individual
eyes. CustomLASIK uses a tool called a wavefront analyzer to
measure the way light travels through your eye. The wavefront
analyzer creates a 3-D map of your eye, this data is then
programmed into the laser to customize your treatment.
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- Lens
- The
lens is the clear structure located behind the pupil. Its primary
function is to provide fine-tuning for focusing and reading, which
it accomplishes by altering its shape.
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Farsightedness (Hyperopia)
- A
refractive error in which you see better from a distance than
close up. Hyperopia is caused by an eyeball that is too short to
focus light on the retina.
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LASIK
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LASIK (Laser-In-Situ Keratomileusis) is currently one of the most
frequently performed elective procedures in North America. It is a
highly effective outpatient procedure that is suitable for low,
moderate and higher prescriptions. In LASIK, a protective hinged
flap is created and gently lifted by the surgeon. Then, a
computercontrolled cool beam of light from the excimer laser is
used to gently reshape the front surface (cornea) of your eye.
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Wavefront Analyzer
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Originally developed for use in high-powered telescopes to reduce
distortions in space, now adapted for eyecare. A single beam of
infrared laser light is passed into the eye and focused on the
retina. The light is then reflected off the retina, passed back
through the eye, through a lenslet array to a sensor, and then
analyzed from 200 different aspects to create a map of the eye -
or fingerprint of vision. This technology uncovers unique
characteristics of the eye never measured before using standard
methods for glasses and contact lenses.
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- Bladeless
LASIK
- In
the LASIK and Custom LASIK procedures, a flap of corneal tissue
must be created and then folded back. With Bladeless LASIK, the
surgeon uses the IntraLase laser to create the corneal flap. This
technology enables the surgeon the ability to customize the
corneal flap for every individual patient.
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Higher-Order Aberrations
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Irregularities, other than refractive errors, that can cause such
problems as decreased contrast sensitivity or night vision, glare
and halos. Higher-order aberrations do not always affect vision.
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Retina
- The
retina consists of fine nerve tissue that lines the inside wall of
the eye and acts like the film in a camera. Its primary function
is to capture and transmit images.
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PRK (Photorefractive Keratectomy)
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Prior to LASIK, PRK was the most common laser vision correction
procedure. For the PRK procedure, the surgeon first removes the
eye's protective first layer of cells, or epithelium, to reveal
the next layer of corneal tissue. The surgeon will apply
computer-controlled pulses of cool light from the excimer laser to
reshape the curvature of the eye. PRK patients require about three
days for the epithelium to heal and allow clearer vision.
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Uncorrected visual acuity (UCVA)
- The
best possible vision a person can achieve without corrective
lenses measured in terms of Snellen lines on an eye chart.
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Monovision
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When, with vision correction, one eye is intentionally left
slightly nearsighted. This allows you to maintain your ability to
read after presbyopia begins. Gaining this near vision means
giving up some distance sharpness.
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- Bilateral
LASIK
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Surgery performed on both eyes.
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