ablate: To remove; often to surgically remove tissue to correct refractive problems such as myopia.
accommodation: Ability of the eye to change focus between near and far objects. Inability to accommodate results in presbyopia.
aqueous humor: Fluid in the front part of the eye (in front of the lens) that provides nutrients and accounts for intraocular pressure.
astigmatic keratotomy (AK): Surgical procedure in which microscopic cuts are made in the cornea so that astigmatism is reduced upon healing.
astigmatism: Uneven curvature
of the cornea that causes light rays to focus in more than one
place. This results in blurred images for both near and distance
vision.
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best corrected visual acuity (BCVA): The measure of your vision while wearing glasses or contact lenses as indicated by the Snellen eye chart.
bifocals: Eyeglasses that have
different prescriptions on the top half and bottom half of the
lenses. People with presbyopia may need bifocals for reading and
other up close work.
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cataract: Medical condition in which the crystalline lens clouds up due to trauma, disease, or age, ultimately interfering with vision. This can be treated with surgery if necessary.
choroid: Blood vessel in the eye that nourishes parts of the retina.
ciliary muscles: Tiny muscles that hold the crystalline lens in place and allow for accommodation. They lose their flexibility with age, resulting in presbyopia.
conjunctiva: Transparent covering on the sclera (outer surface of the eye), also on the inner surfaces of the eyelids.
conjunctivitis: Also known as “pink eye”. Inflammation of the conjunctiva leading to redness, swelling, discharge, and a scratchy sensation.
contrast sensitivity: A measure of the least amount of contrast detectable by the eye.
cornea: Clear part of the eye
that covers the iris and pupil, letting in light. There are 5
layers of the cornea:
1. Epithelium (outermost layer)
2. Bowman’s membrane
3. Stroma
4. Descemet’s membrane
5. Endothelium (innermost layer)
LASIK cuts through the 3 uppermost layers, while LASEK only removes
part of the epithelium.
corneal abrasion: Loss of the epithelial (outermost) layer of the cornea, usually caused by minor trauma such as scratches, injury, or foreign objects in the eye.
corneal topography: Computer-mediated analysis of the contours of your corneas.
crystalline lens: A transparent
inner lens that helps focus light rays onto the retina. Loss of
flexibility in this lens results in presbyopia.
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diopter: A measure of your eye’s
refractive power. A negative number indicates myopia, a positive
number indicates hyperopia. The higher the number, the greater
the refractive problem.
dry eye syndrome. Corneal and conjunctival dryness due to decreased
tear production. Results in foreign body sensation, scratchy eyes,
excessive tearing, and sensitivity to light.
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excimer laser: The laser used
for LASIK and LASEK because of its precision and ability to ablate
tissue without using heat. It emits an ultraviolet beam of light
that is released in pulses. Each pulse removes such a small fraction
of tissue that it would take 200 pulses to cut a human hair.
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farsightedness: See hyperopia.
glaucoma: Disease caused by increased intraocular pressure (pressure inside your eye), resulting in blindness if left untreated.
higher-order aberrations: Aberrations
that interfere with quality of vision by causing night glare,
halos, and problems with contrast sensitivity. Can occur in addition
to myopia, hyperopia, and astigmatism.
hyperopia (farsightedness): Condition in which the length of the eye is too short or the cornea is too flat, causing light rays to focus behind the retina instead of on it. This results in blurred near vision.
intraocular lens: Plastic lens that may be surgically implanted to replace the eye's natural lens.
intraocular pressure: Pressure inside the eye determined by the aqueous humor. High pressure can result in glaucoma.
iris: Pigmented tissue that determines
eye color. Contracts and dilates to control the amount of light
entering the pupil.
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keratoconjunctivitis sicca: See dry eye syndrome.
keratotomy: A surgical cut into the cornea.
LASEK: Laser Epithelial Keratomilieusis. Similar to LASIK in all respects except that it removes only the corneal epithelium, and no surgical incision is made. Good option for patients with thin corneas.
laser: Light Amplification by Stimulated Emission of Radiation. High energy light that is created by the controlled vibration of atoms.
Laser Thermal Keratoplasty (LTK): Surgical procedure to correct hyperopia by use of the heat-producing Holmium laser.
LASIK: Laser In Situ Keratomilieusis. A microkeratome is used to create a flap that cuts through the 3 uppermost layers of the cornea. The flap is replaced after the underlying tissue is ablated.
legal blindness: Best-corrected visual acuity of 20/200 or less, or reduction in visual field to 20¡ or less, in the better seeing eye.
lens: Transparent tissue that
focuses light rays on the retina. Also known as the inner crystalline
lens. The shape of the cornea determines how light passes through
the inner lens, and thus determines how light is focused on the
retina.
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lower-order aberrations: Aberrations such as myopia, hyperopia, and astigmatism, which can be corrected by prescription lenses or refractive surgery.
macula: Small area near the center of the retina that helps you see images in greater detail.
microkeratome: Surgical instrument used for corneal incisions.
monovision: Vision correction procedure for patients with presbyopia. One eye is treated for myopia while the other eye is left nearsighted to handle up close work, such as reading.
myopia (nearsightedness): Condition
in which the length of the eye is too long or the cornea is too
curved, causing light rays to focus in front of the retina instead
of on it. This results in blurred distance vision.
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nearsightedness: See myopia.
OD (oculus dexter): Latin term for right eye. Also indicates Doctor of Optometry.
ophthalmologist: Doctor of Medicine who specializes in the diagnosis and treatment of medical, refractive, and surgical problems related to eye diseases and disorders.
optics: The scientific study of light rays and how they relate to vision.
optician: Professional who is trained in fitting eyeglasses with the lenses prescribed by an ophthalmologist or optometrist.
optic nerve: Main nerve in the eye that transmits signals from the retina to the brain.
optometrist: Doctor of Optometry (OD) specializing in treating vision problems with eyeglasses and contact lenses.
OS (oculus sinister): Latin term for left eye.
OU (oculus uterque, oculus unitas, or
oculus uniter): Latin term for both eyes.
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plano: Term used to describe lenses that have no refractive power, often seen with sunglasses or cosmetic contact lenses.
presbyopia: Condition that develops
around the age of 40-45 in which the ciliary muscles lose flexibility
and the inner crystalline lens is unable to change focus between
near and distant objects.
progressive lenses. Multifocal lenses that change corrective power
gradually and invisibly throughout the lens, without the lines
that traditional bifocals or trifocals have.
pupil: Black opening in the center of the iris that determines the amount of light entering the eye.
pupillary distance: Distance
between the centers of your pupils. Especially important when
having glasses made because the optical center of each lens must
be in front of the center of each pupil. Opticians use a special
ruler to determine this distance.
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refractive error: This term encompasses myopia, hyperopia, astigmatism, and presbyopia; the four main types of eye disorders
retina: Sensory membrane inside the eye that is responsible for receiving images from the lens and sending it through the optic nerve. If light rays do not focus on the retina, a blurred image is transmitted to the brain.
sclera: White part of the eye that is protected by the conjunctiva, stretching from the cornea in the front to the optic nerve in the back.
slit lamp: Microscope designed
for thorough examination of the eye, including the cornea, the
lens, and the retina.
Snellen Eye Chart: Eye chart used to test a patient’s
distance vision. Also known as the chart with the big “E”
at the top.
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vitreous humor: Clear fluid that fills the part of your eye behind the lens.
Wavefront-guided LASIK: A surgical
procedure that is the same as conventional LASIK but which is
tailored for patients who have a greater degree of higher order
aberrations than the average person.
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YAG laser: Laser that is used for surgical procedures in ablating tissue, but is not directly involved in correcting vision.