Glossary of Lasik Laser Eye Surgery Related Terms - Numbers-A

20/20

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.

A

A Scan

Ultrasonic procedure to measure specific areas within the eye.

AAO

See American Academy of Ophthalmology or the American Academy of Optometry.

ABES

See American Board of Eye Surgeons.

Ablation

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.

Ablation Zone

The area of the cornea including the fully corrected optical ablation zone and the transition zone.

ABMD

See Anterior Basement Membrane Dystrophy.

ABO

See American Board of Ophthalmology.

Accommodation

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 called Presbyopia.

Accommodative Insufficiency

Loss of or less than expected amount of accommodation.

ACES

See American College of Eye Surgeons

Acuity

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).

Adnexa

The accessory structures of the eye including the eyelids, lacrimal apparatus, etc.

Advanced Medical Optics

Ophthalmic equipment company.

Aesculap-Meditec

Ophthalmic equipment company. Click here to go to website.

Against-the-rule Astigmatism

"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.

Both 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, blindness.

AK

See Astigmatic Keratotomy.

Alcon

Medical device manufacturer. Click here to go to website.

Algorithm

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.

ALK

See Automated Lamellar Keratectomy.

All-Laser Lasik

Lasik with the corneal flap being created by a femtosecond laser rather than with a mechanical microkeratome. See Bladeless Lasik details

Allegretto

Medical device manufacturer. Click here to go to website.

Allergan

Ophthalmic equipment and drug company. Click here to go to website.

Amblyopia

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 early childhood.

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 restored.

AMD

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 website.

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.

Ametropia

Any imperfection in refractive state of the eye. Examples would be hyperopia (farsighted, longsighted vision), myopia (nearsighted, shortsighted vision), or astigmatism (irregular cornea).

AMO

See Advanced Medical Optics

Amsler Grid

A hand held chart featuring horizontal and vertical lines, usually white on black background, used to test for central visual field defects.

Aniseikonia

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

Anisometropia

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

Anophthalmia

Congenital absence of eyes.

Anopia

Absence of eyes.

Anterior

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 cornea.

Anterior Chamber

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

Antimetropia

A condition in which one eye is myopic and the fellow eye is hyperopic.

Antioxidants

Micro-nutrients that destroy or neutralize free radicals.

AOA

See American Optometric Association.

Aphakia

The absence of the eye's natural crystalline lens, usually after cataract removal.

Aphakic Spectacles

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.

Aqueous Fluid

See aqueous humor.

Aqueous Humor

Clear watery fluid that flows between and nourishes the lens and the cornea. It is secreted by the ciliary processes.

Argon Laser

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.

ARMD

See Age Related Macular Degeneration.

ASCRS

See American Society for Cataract and Refractive Surgery.

Astigmatic Keratotomy

A surgical procedure in which microscopic incisions are placed in the peripheral cornea to create a more spherical shape. Similar to Radial Keratotomy.

Astigmatism

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.

Atopy

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 alcohol.

Anisometropia

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.

Anterior_Chamber

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.

Automated Perimeter

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. 

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