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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
AAO
Abbreviation for American Academy of Ophthalmology or the
American Academy of Optometry.
ABES
Abbreviation for American Board of Eye Surgeons.
ABMD
Abbreviation for Anterior Basement Membrane Dystrophy.
ABO
Abbreviation for American Board of Ophthalmology.
ASCRS
Abbreviation for American Society for Cataract and Refractive
Surgery.
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.
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.
Accommodative Insufficiency
Loss of or less than expected amount of accommodation.
ACES
Abbreviation for 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.
Aesculap-Meditec
Ophthalmic equipment company. .
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
Abbreviation for Astigmatic Keratotomy.
ALK Laser
Automated lamellar keratoplasty (removal of a part of the
central corneal epithelium) combined with excimer laser PRK to effect a
change on the refractive error.
Allergan
Ophthalmic equipment and drug company. .
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
Abbreviation for Age-related Macular Degeneration.
American Academy of Ophthalmology
Ophthalmologist membership organization.
American Academy
of Optometry
Optomotrist membership organization.
American Board of Eye Surgeons
Ophthalmologist certification organization. Affiliated with
the American College of Eye Surgeons.
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".
American College of Eye Surgeons
Ophthalmologist membership organization. Affiliated with the
American Board of Eye Surgeons.
American College of Surgeons
Medical membership organization. Members are called
Fellows. Physicians who are members often use the acronym FACS after their
name.
American Optometric Association
Optometric membership organization. .
American Society of Cataract and Refractive Surgery
Ophthalmologist membership organization. .
Ametropia
Any imperfection in refractive state of the eye. Examples
would be hyperopia, myopia, or astigmatism.
Amsler Grid
A hand held chart featuring horizontal and vertical lines,
usually white on black background, used to test for central visual field
defects.
Angioid
streaks
Crack-like irregularities
that appear in Bruch's membrane.
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
Antioxidants
Micro-nutrients that destroy or neutralize free radicals.
AOA
Abbreviation for 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.
Apheresis
A procedure used to remove
harmful substances from the blood.
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
Abbreviation for Age Related Macular Degeneration.
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 - 1.00 x 30�, 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. 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.
B Scan
Ultrasonic procedure used to check for abnormalities or
locate foreign bodies within the eye.
Barraquer Cyro-Lathe
An instrument used in performing refractive surgery to
correct extreme myopia or hyperopia.
Basement Membrane
A membrane of tissue beneath the epithelium that helps adhere
the epithelium to the Bowman's layer or stromal tissue.
BCVA
Abbreviation for Best Corrected Visual Acuity.
Best Corrected Visual Acuity
This is a measure of best acuity while wearing corrective
lenses like glasses or contact lenses.
Bifocals
Corrective lenses that have two powers of correction.
Typically the majority of the lens is corrected for distance vision while a
small are is corrected for near vision. Bifocals and trifocals are normally
prescribed for individuals with presbyopia.
Binocular
Both eyes.
Binocular Vision
The blending of the separate images seen by each of two eyes
into a single image. Normal binocular vision yields a stereoscopic image and
parallax-induced depth perception.
Black Box Laser
Common term used for a laser built by its owner or by a firm
not approved by the FDA.
Blank spots
A commonly reported symptom
of macular degeneration in which patients report that areas of their view
disappear.
Blepharitis
A chronic or long term inflammation of the eyelids and
eyelashes, affecting people of all ages. Among the most common causes are
poor eyelid hygiene; excess oil produced by the glands in the eyelids; a
bacterial infection; or an allergic reaction.
Blind Spot
(1) A small area of the retina where the optic nerve enters
the eye; occurs normally in all eyes.
(2) Any gap in the visual field corresponding to an area of
the retina where no visual cells are present. Associated with eye disease.
Blue light
A portion of
the light spectrum of macular degeneration that is suspected of being
harmful to the retina.
Blurring
A commonly reported symptom
of macular degeneration in which patients report that lines or edges of
objects lose their sharpness.
Board Certified
See American Board of Ophthalmology.
Bowman's Layer
A layer of cells of the cornea between the epithelium and
stroma. The Bowman's layer appears to be without specific purpose.
Braille
A system of raised letters.
People who are legally blind read by touching the letters with their
fingers.
Broadbeam
This is a method of applying excimer laser energy. A beam of
energy is applied across the entire ablation zone at one time. See also
variable beam and flying spot.
Buttonhole Flap
A complication of LASIK caused when the microkeratome breaks
through the top of the cornea. C
C-CAP
See Custom Contoured Ablation Pattern
Canthus
Demarcation between the sclera and nasal corner of the eye.
Cataract
Opacity or clouding of the natural crystalline lens that may
prevent a clear image from forming on the retina. Cataracts occur naturally
and can be induced by trauma. The cataractous lens may require surgical
removal if visual loss becomes significant, with lost optical power replaced
with an intraocular lens.
Central Ablation Zone
See Optical Ablation Zone.
Central
atrophy
A thinning of the retina
that occurs as part of macular degeneration.
Central Island
A complication of photorefractive keratectomy where the laser
fails to remove a portion of cornea. If one views the concave area of the
ablation like a lake one can imagine an island sticking up in the center-
the visual symptoms would be monocular double vision or distortion.
Central Retinal Artery
The blood vessel that carries blood into eye; supplies
nutrition to the retina.
Central Retinal Vein
The blood vessel that carries blood from the retina.
Central serous
retinopathy
A malfunction of the retinal
pigment epithelium that allows fluid to leak under the retina, causing a
limited retinal detachment.
Central Vision
See visual acuity.
Chiron
Ophthalmic equipment company. .
Choroid
The layer filled with blood vessels that nourishes the
retina; part of the uvea.
Choroidal
neovascularization
A type of set macular
degeneration characterized by rapid leaking of fluids under the retina and
rapidly appearing visual problems.
Ciliary Muscles
The muscles that relax the zonules to enable the crystalline
lens to change shape for focusing.
Ciliary Processes
The extensions or projections of the ciliary body that
secrete aqueous humor.
CK
See Conductive Keratoplasty
CLAPIKS
See Contact Lens Assisted Pharmacologically Induced Kerato
Steepening
Clear Lens Replacement
Clear Lens Replacement (CLR) is essentially cataract surgery
without the cataract. The natural lens is removed from the eye and replaced
with a clear plastic lens. Cataract surgery is done because the lens has
become cloudy. CLR is done for purely refractive purposes.
Clinical Trial
An investigative process under the jurisdiction of the FDA
whereby device or medicine manufacturers sponsor experiments on people for
the purpose of proving or disproving that the device or medicine performs as
expected.
CLR
Abbreviation for Clear Lens Replacement.
COAS
See Complete Ophthalmic Analysis System
Collarette
Color ring around the pupil.
Color Vision
The ability to perceive differences in color, including hue,
saturation and brightness.
Comanagement
When two or more doctors provide care to a patient. In
refractive surgery it is common for an optometrist to provide preoperative
testing and postoperative care with an ophthalmologist providing only the
surgery.
Concave Lens
A lens with a hollow shape like the inside surface of a ball.
Concave lenses are minus power lenses and are used to correct myopia or
nearsightedness.
Conductive Keratoplasty
A refractive surgery procedure for hyperopia and astigmatism
that uses a probe to apply high frequency radio waves into the corneal
tissue, causing shrinkage. This controlled shrinkage will reshape the
cornea to accommodate refractive error.
Cones, Cone Cells
One type of specialized light sensitive cells
(photoreceptors) in the retina that provides sharp central vision and color
vision. Also, see rods.
Conformer
Plastic or silicone shell usually inserted after eye removal
to help form the socket and support the eyelids.
Conjunctiva
The thin transparent mucous membrane that lines the inner
surface of the eyelid and covers the white surface of the eye.
Conjunctivitis
Inflammation of the conjunctiva. May be caused by bacteria,
virus, allergens, or chemical or ultraviolet light exposure.
Contact Lens
Lens made of glass or plastic designed to maintain contact on
the surface of the cornea. Usually used to correct refractive error.
Contact Lens Assisted Pharmacologically Induced Kerato
Steepening
A process of accommodating hyperopic overcorrection following
LASIK, PRK and RK, by molding the cornea with a tight fitting contact lens
and nonsteroidal anti-inflammatory drugs.
Contact Lens Disinfectant
An agent that kills surface bacteria and microorganisms on
contact lenses.
Contact Lens, Daily Wear
Contact lenses designed to be worn only during waking hours.
Frequent & planned replacement contact lenses general term used to refer to
contact lens regimens in which lenses are replaced on a planned schedule,
either every two weeks, monthly or quarterly.
Contact Lens, Disposable
Contact lenses defined by the U.S. Food and Drug
Administration as a contact lens that is used one time and discarded. These
can be worn either for a single day or up to seven days, depending on wear
schedule prescribed by the eye care professional. Any lens that is intended
to be removed from the eye, cleaned, rinsed, disinfected, and reinserted
does not qualify for inclusion in this category.
Contact Lens, Extended Wear
Contact lenses designed to be worn around-the-clock for
intervals of one to seven days.
Contact Lens, Therapeutic
Contact lenses designed to aid in protecting and helping a
sick eye to heal. These unique lenses are frequently combined with precise
medication delivery schedules to heal the eye.
Contact Lens, Toric
Contact lenses designed to correct astigmatic refractive
errors. Toric lenses are weighted to maintain a specific axis across the
cornea.
Contrast Sensitivity
The ability to perceive differences between an object and its
background.
Convergence/Divergence
The turning of the eyes inward/outward so that they are both
"aimed" toward the object being viewed.
Convex Lens
A lens with a bulging surface like the outer surface of a
ball. Convex lenses are plus power lenses and are used to correct hyperopia
or farsightedness. Also used for reading glasses as required for presbyopia.
Cornea
The outer, transparent, dome-like structure that covers the
iris, pupil, and anterior chamber. The cornea provides approximately
two-thirds of the optical power of the eye. Light passes into the eye
through the cornea allowing vision. Light also passes out of the eye
allowing the iris and pupil of the eye to be seen. The cornea can be
considered to have five layers:
1. The
corneal epithelium
2.
Bowman's layer
3.
Corneal stroma
4.
Descemet's layer
5. The
corneal endothelium.
Corneal Abrasion
A scratch or similar trauma to the outer surface of the
cornea.
Corneal Haze
When the cornea becomes cloudy with opaque white cells,
creating vision that is similar to looking through fog.
Corneal Remodeling
The healing of a wound of the cornea.
Corneal Topographical Map
A map of the corneal topography that shows the surface
profile of the cornea.
Corneal Topography
A process of mapping the surface details of the cornea with a
unique camera/computer combination.
Council for Refractive Surgery Quality Assurance
A nonprofit consumer/patient organization that certifies
refractive surgeons based upon refractive surgery outcomes and educates the
public about refractive surgery.
Credentials
In the healthcare industry credentials means the education,
licensure, and professional history of a healthcare provider.
CRSQA
Abbreviation for Council for Refractive Surgery Quality
Assurance. Pronounced "SURS-kah".
Crystalline Lens
The natural lens of the eye, located behind the iris, which
helps bring rays of light to focus on the retina. The original state of the
lens is transparent, but the lens becomes cloudy with age (cataract). The
lens has the ability to vary its power to accommodatively focus light from
objects closer than optical infinity.
Custom Contoured Ablation Pattern
The customization of laser vision correction treatments for
decentered ablations and similar corneal aberrations. The Food and Drug
Administration has approved the use of Custom Contoured Ablation Pattern
(C-CAP) method under a Humanitarian Device Exemption.
Physicians who use the device can perform a treatment
precisely controlled by size, depth and location, making it possible to
reshape the cornea for optimum correction, officials said. Physicians are
able to address decentrations and similar problems resulting from a previous
treatment on most types of refractive surgery.
Custom Cornea
The trade name for the use of a wavefront guided custom
ablation with the LADARVision excimer laser built by Alcon.
Cyclopegic Refraction
An examination of the eye to determine refractive error while
the natural crystalline lens of the eye is paralyzed and unable to
accommodate.
Cyclorotation
See Cyclotorsion.
Cyclotorsion
When eyes rotate clockwise or counterclockwise. This often
occurs when a person changes from vertical (standing or sitting up) to
horizontal (lying down) position.
Day Blindness
Common term for Hemeralopia.
Decentration
A complication of refractive surgery. In perfect centration,
the center of the corneal ablation exactly coincides with the center of the
visual axis and/or pupil. This is like looking through the very center of
your spectacle lens. If you look through the periphery of your lens, you
might end up seeing partly through the lens and partly through the edge of
the lens - this is decentration. Decentration can cause various symptoms
including edge glare or even monocular double vision. Other factors such as
the normal size of the pupil, whether it is dark out (your pupil will
enlarge), or the size of the ablation zone will affect the severity or
presence of symptoms.
Descemet's Layer
Layer of cells in the cornea above the corneal endothelium.
Depth Perception
The ability of the vision system to perceive the relative
positions of objects in the visual field. This ability to determine the
distance of an object is provided by the two eyes receiving slightly
different images due to their wide positioning on the face. The two images
are compared by the brain to calculate distance.
Diabetes Mellitus
A chronic metabolic disorder characterized by a lack of
insulin secretion and/or increased cellular resistance to insulin, resulting
in elevated blood levels of simple sugars (glucose) and including
complications involving damage to the eyes, kidneys, nervous system and
vascular system.
Diabetes Type I
Insulin dependent, resulting from destruction of the insulin
producing pancreatic islet cells.
Diabetes Type II
Non-insulin dependent, resulting from tissue resistance to
insulin.
Diabetic Retinopathy
Diabetic retinopathy damages the tiny blood vessels that
supply the retina. In the early stages of this disease-called non-proliferative
or "background" retinopathy, the retinal vessels weaken and develop bulges
that may leak blood or fluid into the surrounding tissue.
Diffuse Lamellar Keratitis
Also called Sands of Sahara due to the appearance of dunes of
sand in the cornea with advanced stages. DLK is an inflammation under the
LASIK flap of the cornea which is believed to be caused by a response to the
presence of sterile infiltrates in the flap interface.
The complication occurs in the early post-operative period,
vision is hazy and the eye is painful and teary. There is also an
intolerance of bright light.
Dilation
A process by which the pupil is enlarged. Allows more light
to the interior of the eye.
Diopter
A unit of measure of the refractive power if a lens. A one-diopter
lens will focus parallel light rays one meter from the lens and a two-diopter
lens will focus one-half of a meter from the lens. A plus 1.0 diopter lens
is convex and will converge the light rays so they focus as a visible image
1 meter past the lens. A minus 1.0 diopter lens is concave and will diverge
or spread light. The minus lens will not actually focus as a visible image
on an optics table. Its image is known as a virtual image and if the
diverging rays were followed to their point of origin, they would focus one
meter in front of the minus lens.
Diplopia
A condition in which a single object is perceived as two;
also called double vision. Usually with both eyes open as in binocular
diplopia, but can be with only one eye as in monocular diplopia.
DLK
An abbreviation for Diffuse Lamellar Keratitis.
DO
Abbreviation for doctorate of osteopathy.
Doctorate of Osteopathy
A certificate affirming that the holder has achieved the
training required to be a medical doctor through a school of osteopathy.
Dominant Eye
The dominant eye is the eye that looks directly at an object.
The non-dominant eye is the eye that looks at an object from the side.
Double Image
Also called ghosting. If you look at a clock and some of the
numbers have a lighter image just off to the side, this is a typical double
image problem.
Drusen
Tiny yellow or white
deposits of debris that accumulate within Bruch's membrane (of the retinal
pigment epithelium). Common after age 60 and an early sign of age-related
macular degeneration.
Dry Eyes
A condition where either not enough tears are produced or
tears dissipate too fast.
EBMD
Abbreviation for Epithelial Basement Membrane Dystrophy. See
Anterior Basement Membrane Dystrophy.
ECCE
Abbreviation for Extracapsular Cataract Extraction.
Ectasia
An outward bulging of the cornea due to internal pressures
and/or a weakened cornea.
Edema
Swelling.
Emmetropia
Refractive condition in which no refractive error is present
and distant images are focused sharply on the retina with no need for
corrective lenses. Perfect vision or 20/20.
endo...
A prefix meaning within or inside.
Endophthalmitis
An inflammation within the eye. Inflammations may be caused
by organisms such as bacteria or may be sterile as in immune disorders.
Endophthalmitis usually indicates an infectious disease, but occasionally
occurs as a complication of surgery.
Endothelium
The inner layer of cells on the inside surface of the cornea.
Enhancement
Secondary refractive surgery treatments made to refine or
improve the original visual result. Outcome predictability is reduced at
higher corrections. Higher corrections and wider optical zones require
deeper sculpting and consequently undercorrection and overcorrection are
more common. Enhancement treatment by contrast is usually a small correction
and usually has higher outcome predictability.
Enucleation
Surgical removal of the eye.
Ephiphora
A watering of the eyes due to excessive secretion of tears or
to obstruction of the lacrimal passages.
Epithelium
The outer surface layer of the cornea, like the epidermis or
outer layer of the skin.
Epithelium Basement Membrane Dystrophy
See Anterior Basement Membrane Dystrophy
Epithelial Ingrowth
A complication of refractive surgery when epithelial cells
under the flap begin to grow and multiply causing visual abnormalities and
if sever, loss of visual acuity. The most common treatment is lifting the
flap, removing the cells, irrigation of the interface, and repositioning of
the flap.
Esophoria
The position of the eyes in an over-converged position
compensated by the external eye muscles so that the eyes do not appear
turned inward.
Esotropia
The position of the eyes in an over-converged position so
that the non-fixating eye is turned inward.
Excimer Laser
An argon-fluoride laser that emits ultraviolet light that is
emitted in pulses at a wavelength of 193 nm. The term Excimer comes from the
concept of an energized molecule with two identical components or excited
dimer (contracted to one word exci-mer). Each pulse of this his "cool" laser
removes 1/4000 millimeter of tissue from the targeted surface by breaking
intra molecular bonds in collagen molecules. It would take about 200 pulses
from an Excimer laser to cut a human hair in half. This laser was originally
developed for use in the microprocessor industry and later found its
application in vision correction.
Exophoria
The position of the eyes in an over diverged position
compensated by the external eye muscles so that the eyes do not appear
turned outward.
Exotropia
The position of the eyes in an over diverged position so that
non-fixating eye is turned outward.
External Ocular Muscles
The six muscles that turn the eyes to position them for
viewing.
Extracapsular Cataract Extraction
A surgical procedure that removes the cataractous lens of the
eye but leaves the posterior lens capsule intact.
Exudate
A clear fluid.
FACS
Abbreviation for Fellow of the American College of Surgeons.
Farsightedness
Common term for hyperopia.
FDA
Abbreviation for Food and Drug Administration.
Feeder vessel
treatment
Stopping retinal bleeding by
closing the blood vessels that supply the leaking blood vessels.
Fibrosis
The process the body uses to
create scar tissue.
Flap & Zap
Slang term for LASIK.
Fluorescein Angiography
A test to examine blood vessels in the retina, choroid, and
iris. A special dye is injected into a vein in the arm and pictures are
taken as the dye passes through blood vessels in the eye.
Fluorescein Staining
A tiny amount of a fluorescein dye is placed in the tear
film. The color will make microscopic dots appear where the eye has become
dry. Excessive staining is an indication of dry eye.
Flying Spot
This is a method of applying excimer laser energy. Rather
than applying all excimer energy in a broadbeam across the entire ablation
area, or the energy in variable spots sizes across the ablation area, a very
small spot of excimer energy is applied in rapid succession at different
locations across the ablation area.
Focusing Power Of The Eye
As light enters our eye, it must be brought to a focus on the
retina in order to perceive a clear image. About two thirds of the focusing
power of the eye comes from the cornea, the rest comes from the lens inside
the eye. As the light enters the eye, it is focused a fixed amount by the
cornea. As the light passes through the pupil, the lens then adjusts the
focus a variable amount with the exact amount of focusing power applied
dependent on the distance of the object being viewed. Objects at near like a
book or knitting require more power than distance objects like movies or
traffic signs.
Food and Drug Administration
The federal agency of the United States government
responsible for the evaluation and approval of medical devices. The FDA
does not evaluate surgical procedures that to not require a new medical
device. .
Fovea
The central part of the macula that provides the sharpest
vision.
Freeradical
Molecules that have been implicated as one causative factor
in the stimulation of abnormal cellular reproduction (cancer) and cellular
destruction (aging).
Functional Visual Disability
The degree to which a visual error interferes with a person's
ability to perform normal daily activities, such as reading, driving at
night, or performing hobbies.
Fundus
The interior lining of the eyeball, including the retina,
optic disc, and macula. This portion of the inner eye can be seen during an
eye examination by looking through the pupil. G
GASH
Abbreviation for refractive surgery complications glare, arc,
starburst, and halo.
Gaussian
This is a profile of how excimer energy is applied. Used
primarily on flying spot lasers, more energy is applied to the center of the
spot than at the outer edges.
Gene therapy
A method using genes
(sequences of DNA) to treat disease.
Ghosting
This is a common term for double images. If you look at a
clock and some of the numbers have a lighter ghost image just off to the
side, this is ghosting.
Glaucoma
A disease characterized by increased pressure within the
eyeball. more If not diagnosed and treated, glaucoma may lead to optic nerve
damage, loss of visual field, gradual vision impairment, and sometimes
blindness.
Gonioscopy
A diagnostic procedure using a mirror/lens device placed
directly upon the cornea that is used to view the drainage area through
which aqueous fluid exits the eyeball.
Gray Box Laser
Common term used for a laser imported from outside the United
States. This type of acquisition is not approved by the FDA.
Halos
A known complication of refractive surgery that causes images
from light sources to blur with circles radiating out from the center.
Halos also occur naturally without refractive surgery.
Haze
An opacification or cloudiness of the normally clear cornea.
Any build up of inflammatory infiltrates (white blood cells), extra
moisture, scar tissue, or foreign substances (like drugs) can cause a
clouding of the cornea.
Hemeralopia
Day blindness. Often caused by clouding or opacity of one or
more of the normally clear ocular tissues.
Humanitarian Device Exemption
A Humanitarian Device Exemption from the Food and Drug
Administration authorizes the use and marketing of a device that is intended
to benefit patients in the treatment of conditions that affect fewer than
4,000 individuals.
Hyperopia
Also known as farsightedness or longsightedness. Hyperopia
occurs when the eyeball is too short from front to back, or the eye's
focusing mechanism is too weak, causing light rays to be focused behind,
rather than on, the retina. People with hyperopia have difficulty seeing
objects close up. This refractive abnormality requires a plus (positive or
convex) lens for correction.
Hypoxia
A deficiency of oxygen supply to a tissue.
Idiopathic
A disease of unknown origin
or without apparent cause.
Idiopathic
macular degeneration
An extremely rare form of
macular degeneration that affects people in their twenties and thirties.
Intraocular
lens (IOL)
Plastic lens that may be
surgically implanted to replace the eye's natural lens.
Intraocular Pressure (IOP)
Pressure within the eye. High intraocular pressure is called
glaucoma.
Intrastromal Corneal Ring Segments
Trade name Intacs; the implantation of small slivers of
plastic at the outer edges of the cornea to flatten the center of the cornea
and reduce myopia. Intacs have also been found to have therapeutic effect
for keratoconus patients.
Intravitreal
bubble
A gas bubble sometimes
introduced into the eye to displace or stop retinal bleeding. This technique
is also commonly used in the repair of retinal detachment.
IOL
See Intraocular Lens
IOP
See Intraocular Pressure
Iris
Pigmented tissue lying
behind the cornea that gives color to the eye (e.g., blue eyes) and controls
amount of light entering the eye by varying the size of the pupillary
opening.
JCAHO
Abbreviation for Joint Commission on Accreditation of
Healthcare Organizations.
Joint Commission on Accreditation of Healthcare Organizations
The Joint Commission evaluates and accredits more than 18,000
health care organizations and programs in the United States. . K
Keloid
An abnormal scaring of damaged tissue.
Keratectomy
Surgical excision (removal) of any portion of the cornea.
Keratitis
Inflammation of the cornea.
kerato...
A prefix indicating relationship to the cornea.
Keratoconjuntivitis
An inflammation (infectious or auto-immune) of the cornea and
conjunctiva.
Keratoconus
A disorder that involves a thinning of the central cornea.
The normally round shape of the cornea becomes distorted. A cone-like bulge
develops, resulting in significant visual impairment.
Keratometry
The measurement of the curvature of the cornea.
Keratomileusis
A refractive surgical technique where a partial thickness
circular flap of cornea is removed, frozen, reshaped on a lathe and replaced
upon the cornea. The lathe can shape either a convex or a concave lens.
Keratotomy
A surgical incision of the cornea as in Radial Keratotomy.
Lacrimal Gland
The small almond-shaped structure that produces tears;
located just above the outer corner of the eye.
LASEK
See Laser Assisted sub-Epithelium Keratomileusis.
Laser
An acronym for Light Amplification by the Stimulated Emission
of Radiation. Laser light is different from ordinary light in that it is
composed of one color (wavelength) traveling in one direction and each light
wave is traveling in step with the adjacent wave making the laser light more
powerful by a factor of millions. This energy is carried by the wave in
"packets" called photons.
Laser Assisted In-Situ Keratomileusis
An advanced laser procedure combining ALK and PRK to reshape
the central cornea, thereby decreasing or eliminating myopia, hyperopia, and
astigmatism. The refractive surgeon uses an automated microkeratome to shave
off a thin, hinged layer of the cornea. This flap is then lifted like a
hinged door and the exposed surface is reshaped using the excimer laser.
After altering the corneal curvature, the flap is replaced and adheres
without stitches.
Laser Assisted sub-Epithelium Keratomileusis
Laser Assisted Epithelium Keratomileusis is the detachment of
the epithelium with the use of an alcohol solution that softens the
epithelium and allows it to be rolled back into a flap. The flap of
epithelium is then be repositioned over the cornea following excimer
ablations.
Laser Thermal Keratoplasty
A non-excimer laser refractive surgery. The office-based
instrument applies two rings of laser energy to the midperiphery of the
cornea. Each ring gently heats collagen in the cornea to change corneal
shape. The application of energy is accomplished without physically
contacting the cornea with instrumentation or other apparatus.
LASIK
Abbreviation for Laser Assisted In-situ Keratomileusis.
Legal Blindness
In the U.S., (1) Visual acuity of 20/200 or worse in the
better eye with corrective lenses. (2) Visual field restricted to 20 degrees
diameter or less (tunnel vision) in the better eye. Note these criteria are
used to determine eligibility for government disability benefits and do not
necessarily indicate a person's ability to function.
Lens
A transparent double convex (outward curve on both sides)
structure between the iris and the vitreous humor. Two structures of the eye
focus light onto the retina. The first is the cornea or front surface of the
eye that provides about 65% of the focusing power of the eye. The human lens
is located behind the iris and in front of the vitreous humor and provides
the remaining focusing power for the eye. In younger patients (usually below
age 45) the lens is able to adjust it's power allowing the eye to change
it's focal length from distance to near.
Lenticular Astigmatism
When the crystalline lens is not symmetrical.
Limbus
The visible borderline between the clear cornea and the white
sclera of the eye. The conjunctival layer that covers the globe also joins
at the limbus.
LTK
Abbreviation for Laser Thermal Keratoplasty.
Lutein
A vitamin that might reduce
the risk of macular degeneration, but which has not yet been proven to do
so.
Low Vision
Visual loss that cannot be corrected with eyeglasses or
contact lenses and interferes with daily living activities.
Macro Striae
Wrinkles in the LASIK flap.
Macula
The small, sensitive area of the central retina; provides
vision for fine work and reading.
Macular Edema
The collection of fluid in and under the macular portion of
the retina causing swelling.
Macular hole
A microscopic hole that can
appear in the macula.
Macular pucker
A thin membrane growing on
the retina that contracts and distorts the retina, resulting in blurred and
distorted vision.
Macular
translocation
A surgical procedure that
relocates the macula away from leaking blood vessels.
Manifest Refraction
An examination of the eye to determine refractive error while
the natural crystalline lens is able to accommodate.
Masks
Most older technology excimer laser machines employ different
kinds of masks to customize, refine, and smooth the corneal surface. Many
machines have an internal constricting diaphragm (like a camera f-stop
mechanism) as an internal mask. Variable rotation of the masks is used to
deal with astigmatism.
MD
Abbreviation for medical doctorate.
Medial
Nasal or towards the nose.
Medical Doctorate
A certificate affirming that the holder has achieved the
training required to be a medical doctor through a school of medicine.
Meditec
A shortened name for Aesculap-Meditec.
Mesopic Pupil Size
The size of a pupil under medium light conditions such as
daylight or a well lit room.
Micro Striae
Also called Bowman's Crinkles. Very small wrinkles in the
flap caused by Bowman's layer constricting.
Micrometer
The term micrometer has replaced the term micron that was
used before 1967.
Micron
A unit of length equal to one-millionth of a meter.
Microkeratome
A surgical device that is affixed to the eye by use of a
vacuum ring. When secured, a very sharp and thin metal blade slides across
the front of the cornea and shaves a small amount of the cornea at a
predetermined depth.
Microphthalmia
Abnormally small size of eye.
Millimicron
A nanometer, or 10 to the -9 power meter. The term
millimicron was used before 1967.
Miosis
Pupillary constriction.
Monovision
A technique to limit the effects of presbyopia by correcting
one eye for near vision and the other for far vision.
Munnerlyn Formula
Named for engineer Charles R. Munnerlyn, Ph.D, who pioneered
the technology for vision correction based on the excimer laser. This is
the basic formula to calculate the amount of tissue that needs to be removed
to affect refractive change.
Mydriasis
Pupillary dilation.
Myopia
Also known as nearsightedness or shortsightedness. Myopia
occurs when the eyeball is too long from front to back, or the eye's
focusing mechanism is too strong, causing light rays to be focused in front,
rather than on, the retina. People with myopia have difficulty seeing
objects far away. This refractive abnormality requires a minus (negative or
concave) lens for correction. N
Myopic
degeneration
An abnormality similar to
macular degeneration that can occur in severely myopic people.
Nanometer
Abbreviation is nm. 10 to the -9 power meters. The term
nanometer has replaced the term millimicron that was used before 1967.
Nasal
Toward the nose.
National Committee for Quality Assurance
An independent, non-profit organization that certifies
credentials verification organizations and accredits managed care
organizations. .
National Eye Institute
A division of the US federal government's National Institutes
of Health. Approximately three-fourths of US eye research funding
originates at the National Eye Institute. .
NCQA
Abbreviation for National Committee for Quality Assurance.
Near Point Of Accommodation
The closest point in front of the eyes that an object may be
clearly focused.
Near Point Of Convergence
The maximum extent the two eyes can be turned inward.
Nearsightedness
Common term for myopia.
NEI
Abbreviation for National Eye Institute.
Neovascularization
The formation of new blood vessels, often fragile and
inappropriate for the location. Long-term use of contact lenses can starve
the cornea of oxygen, causing neovascularization as the body attempts to
provide oxygen through blood vessels.
Nidek
Ophthalmic equipment company. .
Night Blindness
Common term for nyctalopia.
Nyctalopia
Night blindness. Often caused by a deficiency of the retina
due to a lack of vitamin A.
Nystagmus
An eye condition characterized by rapid, jerky eye movements.
O
Occult
choroidal neovascularization
A type of set macular
degeneration characterized by slower leakage of fluids under the retina.
Ocular
histoplasmosis
Scars in the choroids
resulting from infection by a fungus.
Ocular Hypertension
Elevated intraocular pressure.
Ocular Rosacea
The cause of ocular rosacea is not understood but its
symptoms can leave the eyes feeling irritated and "gritty". Patients may
experience redness, tearing or crusting on the lashes.
Off Label Use
A term used for procedures that are legal, but are not
specifically approved for a particular device or drug. An example is LASIK.
The excimer laser is FDA approved for PRK, but not for LASIK, which is a
combination of ALK and PRK. The LASIK procedure comes under the definition
of the practice of medicine (also called scope of practice), so the FDA does
not necessarily need to approve the use of the excimer laser specifically
for LASIK. An easier example is the scalpel. The scalpel is not
specifically approved for all procedures that may require a scalpel, but if
a medical doctor determines the use of this FDA approved tool is
appropriate, then it is okay with the FDA. Some excimer lasers have
received FDA approval specifically for LASIK, but this is more for marketing
purposes than to accommodate any legal requirement.
Ophthalmic
Anything to do with the eye.
Ophthalmic Imaging Systems
Ophthalmic equipment company. .
Ophthalmologist
A medical doctor who specializes in the diagnosis and medical
or surgical treatment of eye diseases. To become an ophthalmologist one must
first obtain a medical degree (M.D. or D.O. in North America) and then
complete further specialty training. A medical degree typically takes 7 or 8
years university training and a specialist certification an extra 3 years in
the USA or 4 years in Canada. Specialist MD's are usually divided into
"medical" and "surgical" disciplines. Ophthalmology is technically a
"surgical" discipline. Some ophthalmologists chose not to perform surgery
and can be called "medical ophthalmologists". An ophthalmologist may also
prescribe eyeglasses and contact lenses.
Ophthalmoscopy
Examination of the internal structures of the eye using an
illumination and magnification system.
Optic Cup
The white, cup-like area in the center of the optic disc.
Optic Disc
The circular area (disc) where the optic nerve connects to
the retina. Also know as the optic nerve head.
Optic Nerve
The optic nerve is a bundle of nerve fibers, about the
diameter of pencil, which passes through the back of the eyeball and
connects to the nerve fiber layer of the retina. It can be observed directly
with an instrument called an ophthalmoscope. The optic nerve carries the
visual messages from the photoreceptors of the retina to the brain.
Optical Zone
The area of the eye through which light passes to the retina.
To reach the retina light must pass through the cornea, aqueous humor,
crystalline lens, and vitreous while passing through the pupil. The optical
ablation zone is the area where a laser has created full refractive error
correction. See also Transition Zone.
Optician
An expert in the art and science of making and fitting
glasses. The optician may also dispense and/or fit contact lenses, depending
on local licensing practices.
Optometric Refractive Surgery Society
Optometrist membership organization. .
Optometrist
A doctor of optometry is a non-medical primary eye health
care provider who specializes in the examination, diagnosis, treatment,
management, and prevention of diseases and disorders of the visual system.
Optometrists today most often complete a bachelor of science degree (with
very specific requirements) followed by an optometry degree program that
requires four to eight years to complete. Patient contact begins in the
second professional year with the final year being a full 12-month
internship. Many optometrists include the provision of contact lens and
spectacle devices as part of their daily practice. The optometrist may also
prescribe medications, depending on local licensing practices.
ORSS
Abbreviation for Optometric Refractive Surgery Society.
Orthokeratology
A non-surgical procedure using contact lenses to alter the
shape of the cornea to effect a change in the refractive error.
Overcorrection
A known complication of refractive surgery where the expected
amount of correction is more than desired. Overcorrection often occurs where
healing regresses less vigorously than predicted.
Oxidation
A process in which certain
by-products of oxygen react with nearby molecules. It is thought to cause
damage to tissues.
Pachemetry
An ultrasonic procedure used to measure the thickness of the
cornea.
PARK
Abbreviation for Photoastigmatic Refractive Keratectomy
Papilledema
Non-inflammatory swelling/elevation of the optic nerve often
due to increased intracranial pressure or the presence of a tumor.
Penetrating Keratectomy
A surgical procedure when a button-like full thickness
segment of the cornea is removed and replaced with a donor cornea from
another person.
Peripheral Vision
The ability to see objects and movement outside of the direct
line of vision.
PAI
See Photoablative Inlay
PERK Study
A multi-center study of radial keratotomy (RK) outcomes
funded by the National Eye Institute. Ten-year results of RK patients who
had the surgery in 1983 were published in Archives of Ophthalmology in
October 1994.
The study found that seven out of ten patients who had the
operation on both eyes no longer wore or required corrective lenses ten
years after surgery, and 85% of patients saw 20/40 or better without
glasses. It concluded that RK is a "reasonably safe operation" that can
"effectively reduce but not eliminate myopia".
The study also found that 43% of patients experienced a
hyperopic shift following surgery over the ten-year period. These patients
typically experienced an improvement in their vision as their refractive
error moved closer to 20/20. It is for this reason that ophthalmic surgeons
will often intentionally undercorrect their patients, then monitor the rate
of healing before performing a follow-up enhancement procedure.
Patients whose vision had achieved full correction or near
full correction through surgery and who experience a hyperopic shift could
become farsighted and need to wear glasses.
Phacoemulsification
A cataract surgical procedure which uses an ultrasonic
vibration to shatter and break up a cataractous lens, making it easier to
remove. The vibration is delivered by an irrigation-aspiration instrument.
In a survey of ASCRS members in 1994, 86% preferred the phacoemulsification
cataract removal technique over the extracapsular cataract extraction
technique. The technique was invented by Charles D. Kelman, MD, and was
first published in 1967.
Phakic
Meaning that the natural crystalline lens of the eye is
present.
Phi-motion Angiography
Phi-motion angiography employs a scanning laser to capture
rapid-sequence images of blood vessels underlying the retina.
Phoropter
An optical instrument containing many lenses which is used to
determine the required power of glasses or refractive error.
Photo Therapeutic Keratectomy
The use of an excimer laser to remove surface tissue of the
cornea for medical or optical treatment reasons.
Photoablation
The "cold" process of tissue removal which occurs with
excimer laser radiation in the 200nm wavelength range. This far-ultraviolet
wavelength possess light photons so powerful that the molecular bonds of the
target tissue both break down and have sufficient extra kinetic energy to
fly off the surface; hence ablation. Microscopic pictures show incredibly
precise cuts with no evidence of tissue burning in adjacent tissue.
Photocoagulation
The process of tissue destruction accomplished by visible
light radiation. Tissue is broken down by the light and "clots" as if it
were cooked.
Photodynamic
treatment
The use of laser beams to
activate special dyes in order to stop retinal bleeding.
Photokeratitis
A painful but temporary
condition of the eye caused by intense light sources, such as an arc welder.
Photophobia
Sensitivity to light.
Photorefractive Keratectomy
A surgical procedure using an excimer laser to reshape the
central cornea to a flattened shape for people who are myopic and a more
curved surface for people who are hyperopic. Photorefractive Keratectomy
techniques may also be used to correct astigmatism.
Photovaporization
The process of tissue destruction as occurs with infra red
light radiation.
Phthisis Bulbi
Shrinking of eyeball following injury, infection, or disease.
Pigment
epithelial detachment
A split occurring in Bruch's
membrane fills with fluid and causes a dome-shaped detachment of the pigment
epithelium underlying the retina, leading to visual distortion or other
symptoms. Pigment epithelial detachments are often associated with macular
degeneration.
Pigment
epithelium rip
A severe condition caused by
a tear in the pigment epithelium, leading to sudden loss of vision. Pigment
epithelial rips are often associated with macular degeneration but can also
result from direct trauma to the eye.
Pinguecula
A yellowish spot seen on the white of the eye at the junction
of the clear cornea and white sclera of the eye. These lesions are usually
caused by ultraviolet radiation. The white surface of the eye cannot "tan"
and therefore cannot protect itself from sunburn.
PK
Abbreviation for Penetrating Keratectomy.
Plano
No refractive error. Normal vision. A diopter of 0.
Polypoidal
choroidal neovascularization
Small swellings within the
walls of blood vessels under the retina burst and cause damage to the
retina.
Posterior
Back surface or behind.
Posterior Capsular Opacification
Opacification of the posterior lens capsule. Sometimes called
a "secondary cataract". Often a consequence of modern cataract surgery. It
occurs when a thin membrane of tissue grows over the remaining capsule
following cataract surgery, and can develop in as many as half of all cases
between several months and several years after surgery. Most often treated
using the YAG laser to ablate a hole in the capsule.
Posterior Chamber
The space between the back of the iris and the front face of
the vitreous; filled with aqueous fluid.
Posterior Optical Segment
The part of the eye behind to the crystalline lens, including
the vitreous, choroid, retina, and optic nerve.
Posterior Vitreous Detachment
The separation of the vitreous body from the retinal surface
due to shrinkage from degenerative or inflammatory conditions or trauma.
Often an age-related condition.
Presbyopia
Part of the normal process of aging. As a person becomes
older, we begin to lose the flexibility of the natural crystalline lens of
the eye and weakness of the ciliary muscle. Presbyopia actually starts at
about age ten. Most people do not begin to experience the effects of
presbyopia until their forties. This loss of flexibility limits the ability
of the eye to change its point of focus from distance to near. Because of
this normal process, people begin to wear bifocals or other reading
correction. The one advantage of mild myopia is the ability to remove your
glasses after the onset of presbyopia and continue to read. Mild myopia
effectively counteracts presbyopia. Refractive surgery does not change
affects of presbyopia.
PRK
An abbreviation for Photorefractive Keratectomy.
Psuedophakic
When the natural crystalline lens of the eye has been
replaced with an artificial lens during cataract surgery or Clear Lens
Replacement.
Pterygium
A scarring condition of the
cornea, caused by exposure to intense sunlight.
PTK
Abbreviation for photo Photo Therapeutic Keratectomy.
Ptygeria
A growth of scar tissue on the cornea. These lesions like
pinguecula are caused by an ultraviolet burn to the surface layer or
epithelium.
Punctal Plugs
Small silicone or plastic plugs that are inserted into any or
all of the punctum.
Punctum
Tear drains around the eye. There are two in the upper lid
and two in the lower lid.
Pupil
Appears as a small black dot in the center of the iris. The
pupil changes its diameter in response to changes in ambient lighting. The
pupil varies the amount of light reaching the retina and the depth of focus
of the eye.
Pupillary Response
The constriction and dilation of the pupil due to stimulation
by light or accommodation. Q R
Radial
Pertaining to the radius or line from a circle center to the
circumference of the circle.
Radial Keratotomy
A surgical procedure that permanently alters the shape of the
cornea by placing microscopically thin relaxing incisions in the peripheral
cornea. The incisions cause the central portion of the cornea to flatten,
thereby reducing the power of the cornea.
Receptors
Sites in the brain that
allow the attachment of certain drugs, making them active and able to
produce the desired results.
Refractec
Manufacturer of ophthalmic equipment for Conductive
Keratoplasty. .
Refraction
(1) A
test to determine the best eyeglasses or contact lenses to correct a
refractive error (myopia, hyperopia, or astigmatism).
(2)
The bending of light by the use of lens or other material.
Refractive Error
The degree to which images received by the eyes are not
focused on the retina (myopia, hyperopia, or astigmatism) measured in
diopters.
Refractive Surgery
Any surgical procedure which permanently alters the focusing
power of the eye in order to change refractive errors. Refractive surgery
may include corneal surgery such as LASIK, LASEK, PRK, Intacs, CK, LTK or
lens surgery such as CLR or Phakic IOL
Regression
A return by the cornea toward the original refractive state.
Retina
The light sensitive layer of cells (rods and cones) on the
inner back surface of the eye that converts light images into nervous
impulses sent along the optic nerve for transmission to the brain.
Retinal Axons
The nerve fiber extensions of the retinal photoreceptors that
form the nerve bundle called the optic nerve.
Retinal Detachment
A separation of the neural tissue of the retina from the
pigmented epithelium layer and therefore the blood supply. Results in loss
of vision in the detached area. Repairable with fair to good prognosis for
vision if diagnosed in the early stages.
Retinal
fibrosis
Scarring in the retina.
Retinal Pigment Epithelium (RPE)
The pigment cell layer that nourishes the retinal cells;
located just outside the retina and attached to the choroid.
Retinitis Pigmentosa
The name given to a group of disorders of the Retina, all of
which result in a progressive reduction in vision.
RK
Abbreviation for Radial Keratotomy.
Rods, Rod Cells
One type of specialized light sensitive cells
(photoreceptors) in the retina that provide side vision and the ability to
see objects in dim light (night vision). Also, see cones.
Saline Solution
A sterile salt solution used in cleaning, rinsing, and
sometimes storing of contact lenses.
Sands of Sahara
See Diffuse Lamellar Keratitis.
Schlemm's Canal
The passageway for the aqueous fluid to leave the eye.
Sclera
The tough, white, outer layer (coat) of the eyeball. With the
cornea, it protects the entire eyeball.
Scleral Shell
Flush fitting thin artificial eye usually fit over phthisis
bulbi.
Scotopic Pupil Size
The size of a pupil under low light conditions similar to
light in a theater or during night driving.
Scotoma
An area of partial or complete loss of vision surrounded by
an area of normal vision.
Secondary Implant
If no lens was placed in the eye at the time of cataract
removal surgery, then a secondary procedure to implant an intraocular lens
may be completed later.
SEE
Abbreviation for Society for Excellence in Eyecare.
Shirmer Test
Tiny strips of filter paper are placed in the patient's eyes
just under the lids. After five minutes the distance the tears have stained
the paper is measured. The greater the distance, the higher the natural
tear production.
Side Vision
See peripheral vision.
Slit Lamp
A microscope using various magnifications combined with a
strong light that can be focused into a slit for examining the eye.
Snellen Visual Acuity Test
The white chart with the big black E at the top and lines of
letters that become increasingly smaller. The Snellen Test is one of many
tests used to determine visual acuity. The term 20/20 means that the
patient can see an item 20 feet away with the same clarity that a normally
sighted person can see an item 20 feet away. 20/40 means that the patient
can see an item 20 feet away with the clarity that a normally sighted person
can see an item 40 feet away. This is worse than normal vision. 20/10
means that the patient can see an item 20 feet away with the same clarity
that a normally sighted person can see an item 10 feet away. 20/10 is
better than normal vision.
Society for Excellence in Eyecare
Ophthalmologist membership organization. .
SOS
See Sands of Sahara.
Strabismus
More commonly known as crossed-eyes, is a vision condition in
which a person cannot align both eyes simultaneously under normal
conditions. One or both of the eyes may turn in, out, up or down. An eye
turn may be constant; when the eye turns all of the time. Strabismus may be
intermittent; turning only some of the time, such as, under stressful
situations or when ill.
Starbursts
A known complication of refractive surgery that causes images
from light sources to blur with spikes radiating out from the center.
Starbursts also occur naturally without refractive surgery.
Stem cell
A type of primitive cell
that can transform into and generate other cells.
Stereopsis
The ability to perceive three-dimensional depth due to the
distance between a person's two eyes.
Steroid
A large class of pharmaceutical agents that chemically
resemble cholesterol. Two better known types are anabolic steroids often
used in athletics, and glucocorticoid steroids that are used to reduce
inflammation.
Stiles-Crawford effect
The Stiles-Crawford effect (discovered in 1933) describes
angular dependence of retinal sensitivity. Rays which enter the pupil near
its center, which are parallel to retinal receptors, are more effective than
oblique rays which enter the pupil near its margins. So, the light passing
through the periphery of the pupil is less efficient at stimulating vision
than the light passing near the center of the pupil. It is believed that
photoreceptors act as light pipes, and more light gets down if it enters
straight down (through the center of the cornea), rather than at a large
angle (through the periphery of cornea).
Striae
Wrinkles in the corneal flap created for LASIK. There are
two kinds, macro striae and micro striae.
Stroma
Thickest layer of cells in the cornea.
Subretinal
hemorrage
A condition caused by
pooling of blood under the retina.
Sulcus
Upper eyelid depression.
Summit
Ophthalmic equipment company. .
Sunrise Technologies
Ophthalmic equipment company. .
Suppression
The inability to perceive all of part of objects in the field
of vision of one eye.
Tear Breakup Test
A test that determines the quality of the tears on the eye.
The doctor observes the tear film under the microscope while the patient
avoids blinking until tiny dry spots develop. The longer the amount of time
that passes before the tear film breaks up, the more stable the tear film. A
good value is more than 10 seconds.
Tear film
A layer of fluid that bathes
and lubricates the cornea.
Temporal
Toward the ear.
TLC, The Laser Center
Chain of refractive surgery centers. .
Tonometry
A procedure for the measurement of the fluid pressure inside
the eye (intraocular pressure). One of the tests for glaucoma.
Topcon
Ophthalmic equipment company. .
Topographic Supported Customized Ablation
A system to use a topographical mapping system to guide the
laser during refractive surgery.
Topography
To measure the high and low areas of a plane. See corneal
topography.
TOSCA
Is the acronym for Topographic Supported Customized
Ablation. This means using a topographical mapping system to guide the
excimer laser ablation.
Trabecular Meshwork
The spongy, mesh-like tissue near the front of the eye that
allows the aqueous fluid to flow to Schlemm's canal then out of the eye
through ocular veins.
Transition Zone
The area of laser ablation that changes for the full
correction of the central ablation zone optical ablation zone to the
original surface depth of the cornea.
Transpupillary
thermotherapy (TTT)
The use of infrared light to
stop retinal bleeding.
Trifocals
Corrective lenses that have three powers of correction.
Typically the majority of the lens is corrected for distance vision while a
small area is corrected for near vision and another small area is corrected
for middle vision. Trifocals and bifocals are normally prescribed for
individuals with presbyopia. U
UCVA
Abbreviation for Uncorrected Visual Acuity.
Ultrasound
Procedures using sound waves to measure certain portions or
detect abnormalities within the eye.
Ultraviolet Radiation
Radiant energy with a wavelength just below that of the
visible light. UV-c is the shortest wavelength at 200-280nm and is absorbed
by the atmosphere before reaching the surface. Extremely damaging to living
tissue. UV-b, at 280-315nm is "burning rays" of the sun and is damaging to
most living tissue. UV-a, at 315-400nm is "tanning rays" of the sun and is
somewhat damaging to certain tissues. UV radiation has been described as a
contributing factor to the processes that results in ARMD, cataracts, and
causes exposure keratitis.
Ultraviolet
(UV) light
The non-visible portion of
the light spectrum with a wave length shorter than violet light.
Uncorrected
Visual Acuity
The best vision measurement taken without the use of glasses
or contact lenses.
Undercorrection
A complication of refractive surgery where the expected
amount of correction is less than desired. Undercorrection often occurs
where healing regresses more vigorously than predicted.
Uvea, Uveal Tract
The middle coat of the eyeball, consisting of the choroid in
the back of the eye and the ciliary body and iris in the front of the eye. V
Variable Spot
This is a method of applying excimer laser energy. Rather
than applying all excimer energy in a broadbeam across the entire ablation
area, or with a very small flying spot of excimer energy applied in rapid
succession at different locations across the ablation area, the energy is
applied in variable spot sizes across the ablation area.
Vector Vision
Ophthalmic equipment company. .
Vision Therapy
A treatment process for the improvement of visual perception
and/or coordination of the two eyes for efficient and comfortable binocular
vision (orthopedics, vision training, and eye exercises).
Visual Acuity
Clearness of vision. The ability to distinguish details and
shapes of objects; also called central vision.
Visual Axis
The
central area of the cornea, pupil, and lens that light passes through to
reach the retina and be "seen".
Visual Field
The area or extent of space visible to an eye in a given
position of gaze. The central visual field is directly in front and the
target at which we are looking. The peripheral visual field is that which we
perceive in our "side vision". The fields of each eye partly overlap.
Visx
Ophthalmic equipment company. .
Vitreous
hemorrhage
Hemorrhage within the
vitreous of the eye.
Vitreous Humor
The transparent, colorless mass of gel that lies behind lens
and in front of retina. W
Wave Length
The distance between the top of one wave and the top of the
next wave. The length of one complete wave of the argon fluoride excimer
laser is 193 nm. This wavelength is in the far ultraviolet end of the
electromagnetic spectrum.
Wet macular
degeneration
The abnormal increase in and
leaking from blood vessels under the retina, leading to disturbances of the
central field of vision.
YAG Laser
YAG is an abbreviation for neodymium yttrium-aluminum-garnet,
the material used generate a short pulsed, high-energy light beam in the
infra red wavelength of 1064 nm. The YAG laser is a surgical instrument that
can be precisely focused by computer to cut, photovaporize, or fragment
tissue. The YAG laser is used to treat posterior capsular opacification; a
clouding of the remaining capsular tissue that develops postoperatively in
as many as 75% of cataract removal operations. The tissue is vaporized with
carefully controlled pulses of the YAG laser, and the surgery is performed
on an outpatient basis. The common misconception that "lasers" are used to
remove cataracts occurs because post-cataract patients eventually require
YAG laser capsulotomy. Z
Zinc
An antioxidant that
neutralizes freeradicals and is important to the proper functioning of the
body. Its role in macular degeneration is unknown.
Zyoptix
The brand name for wavefront guided custom ablation on the
Bausch & Lomb Technolas excimer laser.
Zonules
The fibers that hold the lens suspended in position and
enable it to change shape during accommodation.
Copyright 2003 � Council
for Refract. Surg. Qual. Assurance,
a nonprofit California
corporation.
All Rights Reserved.
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