Glossary of Lasik Laser Eye Surgery Related Terms - Numbers-A
Fraction commonly used to indicate normal vision. A bottom number larger
than twenty indicates diminished vision. For example, a person with 20/400
vision would see a line of text that is twenty feet away with the same
readability that a person with "normal" vision would see that line of text
from 400 feet away.
Ultrasonic procedure to measure specific areas within the eye.
See American Academy of Ophthalmology or the American Academy of Optometry.
See American Board of Eye Surgeons.
Removal. In the case of the excimer laser, the frequency of energy causes
the molecules of the cornea to loose the "glue" that holds them together.
They simply fall away from each other and the remaining cornea.
The area of the cornea including the
fully corrected optical ablation zone and the transition zone.
See Anterior Basement Membrane Dystrophy.
See American Board of Ophthalmology.
The ability of the eye to change focus from distant objects to objects
closer than optical infinity, approximately 20 feet (6 meters). Like when
driving and you switch from looking down the road to reading the
speedometer. Accommodation is achieved when the lens shape is changed by
small muscles around the lens pushing and pulling. Loss of accommodation is
Loss of or less than expected amount of accommodation.
See American College of Eye Surgeons
Clearness, as in visual acuity. The most common measure of visual acuity is
the Snellen acuity chart. Normal acuity being 20/20 (6/6 metric version).
accessory structures of the eye including the eyelids, lacrimal apparatus,
Advanced Medical Optics
Ophthalmic equipment company.
Ophthalmic equipment company. Click here to go to website.
"With the rule" astigmatism has an
axis of about 180 degrees (when Rx is written in minus cylinder form).
"Against the rule" astigmatism has the axis at about 90 degrees.
forms are common. Nevertheless, when looking at population norms, "with the
rule" is more common in young adults while "against the rule" is more common
in older adults.
Age Related Macular Degeneration
Destruction and loss of the photoreceptors in the macula region of the
retina resulting in decreased central vision and, in advanced cases,
See Astigmatic Keratotomy.
Medical device manufacturer. Click here
to go to website.
A precise mathematical rule or set of rules to find a solution to a problem.
In refractive surgery,
algorithm often refers to the mathematical calculations of the excimer laser used to create an ablation patter to reshape the cornea for the
purpose of reducing the need for corrective lenses, such as in Lasik, PRK, LASEK, or Epi-Lasik.
See Automated Lamellar Keratectomy.
Lasik with the corneal flap being created by a femtosecond laser
rather than with a mechanical microkeratome. See Bladeless Lasik details
Medical device manufacturer. Click
here to go to website.
Ophthalmic equipment and drug company. Click here to go to website.
Often called "lazy eye" it is a unilateral (occasionally bilateral)
condition in which, in the absence of any obvious structural anomalies or
ocular disease, the best corrected vision is less than 20/20 (6/6).
Amblyopia is often occurs in an eye that did not have adequate use during
Most often amblyopia results from either a misalignment of a child's eyes,
such as crossed eyes, or a difference in image quality between the two eyes
(one eye focusing better than the other.) In both cases, one eye becomes
stronger, suppressing the image of the other eye. If this condition
persists, the weaker eye may becomes useless.
With early diagnosis and treatment, the sight in the "lazy eye" can be
See Age-related Macular Degeneration.
American Academy of Ophthalmology
Ophthalmologist membership organization.
American Academy of Optometry
Optometrist membership organization.
American Board of Eye Surgeons
Ophthalmologist certification organization. Affiliated with the American
College of Eye Surgeons. Click here to
go to website.
American Board of Ophthalmology
A medical specialty board that administers a 1-1/2 year long education and
examination process for ophthalmologists. After an ophthalmologist has
passed the examination, (s)he is "Board Certified". Click here to go to website.
American College of Eye Surgeons
Ophthalmologist membership organization. Affiliated with the American Board
of Eye Surgeons. Click here to go to
American College of Surgeons
Medical membership organization. Members are called Fellows. Physicians who
are members often use the acronym FACS after their name. Click here to go to website.
American Optometric Association
Optometric membership organization. Click
here to go to website.
American Society of Cataract and Refractive Surgery
Ophthalmologist membership organization. Click here to go to website.
Any imperfection in refractive state of the eye. Examples would be hyperopia (farsighted, longsighted vision), myopia (nearsighted, shortsighted vision), or astigmatism (irregular cornea).
See Advanced Medical Optics
A hand held chart featuring horizontal and vertical lines, usually white on
black background, used to test for central visual field defects.
Aniseikonia is a binocular condition in which left and right images differ
in size or shape. There are two types of aniseikonia – static and dynamic
aniseikonia. The first type is the classical aniseikonia, denoting a
perceived image size difference with a fixed gaze direction. Classic
aniseikonia can occur naturally or be induced by refractive surgery.
The second type of aniseikonia is also called induced anisophoria and
denotes a perceived image size difference due to unequal prism effects when
looking through different parts of the two (anisometropic) spectacle lenses. Detailed
Aniseikonia and Lasik Information
The condition in which the two eyes have an unequal refractive power. One eye may be myopic (nearsighted, shortsighted) and the other hyperopic (farsighted, longsighted). Detailed
Anisometropia and Lasik Information
Congenital absence of eyes.
Absence of eyes.
Front or forward portion.
Anterior Basement Membrane Dystrophy
Also called Epithelium Basement Membrane Dystrophy, is a disease that
disrupts the ability of the epithelium to attach to the lower layers of the
cornea. The epithelium will often grow unevenly or will detach from the
The space in front of the iris and behind the cornea.
Anterior Ocular Segment
The part of the eye anterior to the crystalline lens, including the cornea,
anterior chamber, iris and ciliary body
A condition in which one eye is myopic and the fellow eye is hyperopic.
Micro-nutrients that destroy or neutralize free radicals.
See American Optometric Association.
The absence of the eye's natural crystalline lens, usually after cataract
Thick, plus-powered eyeglasses that were once the standard correction for
optical power following extraction of cataract. The glasses were cumbersome
and greatly distorted peripheral vision. Today, an intraocular lens (IOL) is
implanted in the eye after the cataract is removed.
See aqueous humor.
Clear watery fluid that flows between and nourishes the lens and the cornea.
It is secreted by the ciliary processes.
Laser light produced from argon gas. The main wavelengths are 488.0 nm blue
and 514.5-nm pea green light, but nine separate wavelengths in the
blue-green visible light spectrum are produced.
See Age Related Macular Degeneration.
See American Society for Cataract and Refractive Surgery.
A surgical procedure in which microscopic incisions are placed in the
peripheral cornea to create a more spherical shape. Similar to Radial
A condition in which the surface of the cornea is not spherical, but is
irregularly shaped like the back of a spoon. An astigmatic cornea causes
light images to focus on two separate points in the eye, creating a
distorted image. Symptoms range from visual discomfort in mild cases, to
severe blurring, ghosting, and distortion similar to a reflection in a
fun-house mirror. The amount of astigmatism you have will appear in the
second number of most glasses prescriptions. The angle of direction
(cylinder meridian or axis) of the astigmatism will be shown in degrees. A
prescription of -4.00-1.00x30°, would indicate that you have 1.00 diopter of
astigmatism at 30 degrees axis.
A type of inherited allergic response involving elevated immunoglobulin E.
Sometimes called a reagin response, it means that you have hay fever,
bronchial asthma, or skin problems like urticaria or eczema. It can also be
acquired, sometimes following hepatitis or extended contact with solvents or
The absence of refractive error symmetry between both eyes. If one person's
eye has a refractive error that is more than one diopter greater than the
other, it is called anisometropia.
The anterior chamber is in the front of the eye behind the cornea and in
front of the iris.
Automated Lamellar Keratoplasty
An incisional refractive surgery technique for low to moderate myopia (nearsighted, shortsighted vision). In the procedure, the
refractive surgeon places an instrument called an automated microkeratome on the eye which removes, in a shaving motion, a thin
layer of cornea only microns thick. An even thinner layer of cornea underneath this top cap is removed,
and the top cap is replaced. The procedure does not require sutures.
A computer-driven device used to plot defects in the visual field. Usually
the patient's head is placed into this large hemisphere shell. Various
points of lights, sometimes of different sizes, intensities, and colors are
projected onto the screen. The patient then indicates whether the light is
seen and the response is recorded. The computer then plots the effective
visual thresholds within the targeted visual field.
Autonomous Technologies Corporation
Manufacturer of ophthalmic lasers.
Looking For Best Lasik Surgeon?
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or custom wavefront Lasik, Bladeless Lasik, PRK, or any refractive surgery procedure, we recommend you consider a doctor who has been evaluated and certified by the USAEyes nonprofit organization.
Locate a USAEyes Evaluated & Certified Lasik Doctor.
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