|
If you are new to the world of contact lenses, then
our informative contact lens glossary will give
you some quick answers to common terms. It is recommended
that you visit a qualified eye doctor before ordering
contact lenses online.
ablation Removal. In vision, ablation refers
to the surgical removal of eye tissue to correct a refractive
error such as myopia.
acetate Type of plastic often used in eyeglass
frames.
accommodation Eye's ability to automatically
change focus from seeing at one distance to seeing at
another.
AK (astigmatic keratotomy) Procedure in which
a surgeon cuts the cornea so that is more spherical
when it heals, thus reducing astigmatism.
allergy Sensitivity to a substance, accompanied
by sneezing, itching, watery eyes, difficulty breathing
or rashes.
amblyopia Also called lazy eye. Diminished sight
in one eye.
AMD or ARMD (age-related macular degeneration)
Disorder characterized by the gradual loss of central
vision due to a damaged macula (which is made up of
retinal cones necessary for sight).
angle In glaucoma terminology, "angle" refers
to the drainage channel for the aqueous humor in the
eye; improper drainage can lead to the high intraocular
pressure associated with glaucoma. In narrow-angle glaucoma,
the channel is blocked, whereas open-angle glaucoma
has other causes, such as the body producing too much
aqueous humor.
ANSI Z87.1 The American National Standards Institute's
Practice for Occupational and Educational Eye and Face
Protection; eyewear that meets this standard is considered
safer than eyewear that does not.
anterior chamber Part of the eye behind the
cornea and in front of the iris and lens.
antioxidant Substance that inhibits oxidation
and can guard the body from the damaging effects of
free radicals. Molecules with one or more unpaired electrons,
free radicals can destroy cells and play a role in many
diseases. Antioxidants may help prevent macular degeneration
and other serious eye diseases.
Discount
Contact Lens
antireflective coating (AR coating) Thin layer(s)
applied to a lens to reduce the amount of reflected
light and glare that reaches the eye.
aqueous humor Clear fluid in the eye that both
provides nutrients and determines intraocular pressure.
aspheric Not quite spherical. Aspheric eyeglass
lenses are popular among people who have strong prescriptions
because they are thin and lightweight, and reduce distortion
and eye magnification. Aspheric contact lenses can work
as a multifocal, or to correct a single-vision problem
like astigmatism.
astigmatism Condition caused by an irregularly
shaped cornea, resulting in two focal points (blurred
vision).
aviator glasses Glasses like those that aviators
used to wear; they usually have a metal frame and large,
tinted lenses.
band keratopathy Opacity of the eye's stroma
and Bowman's membrane.
beta titanium Titanium alloy. Beta-titanium
eyeglass frames are both strong and flexible.
bifocal Having one segment for near vision and
one segment for far vision.
blepharitis Condition characterized
by crusting around the eyes upon awakening, itching,
burning, tearing, swollen eyelids and mucus.
Bowman's membrane Corneal
layer between the epithelium and the stroma.
bridge The part of eyeglasses
that extends across the nose.
cable temple Style of eyeglasses
that wraps around the ear, to keep them well-fastened.
Discount
Contact Lens
cataract Clouding of the
natural lens of the eye, resulting in impaired vision.
Cataract surgery involves removing the eye's natural
lens, and replacing it with an artificial one.
central island Refractive
surgery complication in which the laser leaves an "island"
of corneal tissue in the concave ablation zone. Symptoms
include double vision and distortion.
choroid Layer of blood vessels
and pigments (usually brown or blue) that lies beneath
the sclera (the white of the eye). Often mistakenly
called the iris.
CK (Conductive Keratoplasty)
Procedure wherein a surgeon uses radio waves to heat
collagen in the cornea's periphery to shrink it and
reduce hyperopia.
ciliary body Part of the
eye between the iris and the choroid; the three form
the uvea. The ciliary body's main functions are accommodation,
aqueous humor production and holding the lens in place.
clip-on Type of glasses that
attaches to your regular glasses, such as clip-on sunglasses.
CMV retinitis (cytomegalovirus
retinitis) Serious eye infection usually found in those
with immune problems, such as AIDS patients; symptoms
include floaters, blind spots, blurry vision and vision
loss.
collagen Fibrous protein
in bones and connective tissue, it is also present in
the eye. One type of vision correction surgery heats
collagen around the edges of the cornea (which lets
light into the eye). This procedure reshapes the cornea,
helping it focus light right onto the retina, for clearer
vision.
color blindness Partial or
total inability to distinguish specific colors.
computer vision syndrome
Condition caused by prolonged computer use, and characterized
by eyestrain, blurred vision, headaches and dry or irritated
eyes.
cone A photosensitive receptor
in the retina that helps you to see color.
conjunctiva Mucous membrane
that lines the visible part of the eye and the inner
surface of the eyelid.
conjunctivitis Inflammation
of the conjunctiva.
contact lens drops Eyedrops
for contact lens wearers; regular eyedrops can discolor
contact lenses.
contrast sensitivity The
least amount of contrast that you can still see.
convergence Eyes' ability
to turn inward. People with convergence insufficiency
have trouble (eyestrain, blurred vision, etc.) with
near tasks such as reading.
cornea The clear part of
the eye covering the iris and pupil; it lets light into
the eye, permitting sight.
corneal abrasion Tearing
or puncture of the cornea. Usually causes pain, tearing,
light sensitivity, and a feeling that something is in
the eye.
corneal implants Devices
(such as rings or contacts) placed in the eye, usually
to correct vision.
corneal ring Type of vision
correction surgery where a doctor inserts a tiny plastic
ring into the cornea (which lets light into the eye).
This ring reshapes the cornea, helping it to focus light
better onto the retina so you can see better. The ring
can be adjusted and even removed if desired.
corneal topography Process
of using a camera/computer system to map the cornea
for refractive surgery, contact lens fitting and corneal
disease management.
corneal ulcer Wound in the
surface of the eye caused by injury, dryness due to
lack of tear production, or infection.
crossed eyes Type of strabismus
(a misalignment of the eyes) where one or both eyes
point inward, toward the nose.
cystoid macular edema (CME)
Swelling of the eye's macula, caused by an excessive
amount of fluid.
dacryostenosis Blocked tear
duct, which is characterized by a lot of tearing.
daily wear These soft contact
lenses are worn every day for six months up to a couple
of years. They require daily cleaning and disinfecting,
as well as a periodic enzymatic soak (usually once a
week).
decentered ablation Also
called decentration. Refractive surgery complication
in which the laser is not centered on the pupil when
it removes tissue. Symptoms include glare, double vision
and halos.
Descemet's membrane Corneal
layer between the stroma and the endothelium.
diabetic retinopathy Leaking
of retinal blood vessels in advanced or long-term diabetes,
affecting the macula or retina. Vision can be seriously
distorted or blurred.
diopter Unit which measures
the refractive (light-bending) power of a lens; eyecare
practitioners use it in eyeglass and contact lens prescriptions.
A negative number refers to nearsightedness, while a
positive number refers to farsightedness. For example,
someone with -8.00 diopter lenses is very nearsighted,
while someone with +0.75 diopter lenses is only slightly
farsighted.
disposable contact lenses
Technically, this is any contact lens that is thrown
away after a short period of time. Among most eyecare
practitioners, "disposable" usage ranges from one day
to two weeks, while "frequent replacement" lenses are
discarded monthly or quarterly.
drooping eyelids Also called
ptosis. Condition in which the upper eyelid(s) only
sag. It can be present at birth or caused by a later
problem with the muscles lifting the eyelid, called
levators.
druse Small yellow or white
deposit in the eye. Drusen are sometimes signs of macular
degeneration.
dry eye Lack of sufficient
lubrication and moisture in the eye. Most dry eye complaints
are temporary and easily relieved; dry eye syndrome
is chronic and needs more advanced treatment by an eyecare
practitioner.
endothelium The cornea's
inner layer of cells.
enzymatic cleaner A cleaner
that removes protein deposits and other debris from
contact lenses. It's recommended for use either daily,
weekly, or monthly. Some enzymatic cleaners are a small
tablet dropped into a solution along with the lens;
others come in liquid form.
epithelium The cornea's outer
layer of cells.
extended wear Currently,
these contact lenses are FDA-approved to be worn without
removal for up to seven days (or 30 days in the case
of two brands), meaning some people will be comfortable
sleeping with them in their eyes. Thirty-day contact
lenses are sometimes referred to as "continuous wear."
eyecare practitioner Optometrists
(O.D.s) and ophthalmologists (M.D.s) both practice eyecare,
but in different ways: O.D.s (Doctors of Optometry)
examine eyes for both vision and health problems, prescribe
glasses, prescribe and fit contact lenses, and treat
some eye conditions and diseases. M.D.s are medical
doctors who examine eyes, prescribe glasses and contacts,
treat disease and perform surgery. Other non-doctor
eyecare practitioners include paraoptometrics, contact
lens technicians and opticians.
farsightedness Also called
hyperopia. To farsighted people, near objects are blurry,
but far objects are in focus.
FDA (Food & Drug Administration)
A United States government body that oversees medical
devices, including contact lenses, intraocular lenses,
excimer lasers and eyedrops. In the U.S., these products
must be approved by the FDA before they can be marketed.
flap and zap Slang for LASIK.
floaters Small specks that
pass across your field of vision, these are clumps of
cells inside the transparent gel filling the eyeball
in front of the retina.
fovea A depression in the
retina that contains only cones (not rods), and that
provides acute eyesight.
frequent replacement contact
lenses Also called planned replacement. Technically,
this is any contact lens that is thrown away after a
moderately short period of time. Among most eyecare
practitioners, "disposable" usage ranges from one day
to two weeks, while "frequent replacement" lenses are
discarded monthly or quarterly.
glaucoma Disease characterized
by excessive fluid (aqueous humor) in the eye, high
intraocular pressure and vision impairment. Blindness
can result.
Graves' ophthalmopathy Thyroid-related,
autoimmune eye disorder usually associated with Graves'
disease; symptoms include eyelid retraction, bulging
eyes, light sensitivity, discomfort, double vision and
vision loss.
hard contact lenses Rarely
worn now, these are the small, hard lenses made of PMMA
material that many people wore in the '70s and '80s.
Compared with modern soft and rigid lenses, they are
less healthy to wear long-term, since the material doesn't
allow oxygen to reach the surface of the eye.
high index Type of lens with
a higher index of refraction, meaning that light travels
faster through the lens to reach the eye than with traditional
glass or plastic. It is denser, so the same amount of
visual correction occurs with less material (whether
glass or plastic) — so the lens can be thinner.
hyperopia Also called farsightedness.
To people with hyperopia, near objects are blurry, but
far objects are in focus.
intraocular lens (IOL) Artificial
lens that a cataract surgeon places in a patient's eye
after removing the eye's natural lens. Like a contact
lens, it has a built-in refractive power tailored specifically
to the patient's visual condition.
intraocular pressure (IOP)
Eye pressure, as determined by the amount of aqueous
humor filling it. High IOP (ocular hypertension) can
be a sign of glaucoma.
iris Diaphragm that controls
the size of the pupil (an opening that lets light in).
Many people believe the iris is the colored part of
the eye. Actually, that is the choroid, a pigmented
layer beneath the sclera (white of the eye).
iritis Inflammation of the
iris.
keratectomy Surgical removal
of part of the cornea.
keratitis Inflammation of
the cornea.
keratoconus Condition in
which the cornea develops a cone-shaped bulge that can
result in major blurring and distortion.
keratoplasty Any of several
types of corneal surgery, such as shrinking the collagen
to reduce farsightedness or transplanting a new cornea
to treat keratoconus.
keratotomy Incision of the
cornea.
lacrimal plug Device to block
the lacrimal punctum (an opening at the end of a tear
duct), to keep the eye moist.
laser photocoagulation Procedure
in which a surgeon uses a laser to coagulate tissue,
usually to seal leaking blood vessels and destroy new
ones in diseases like macular degeneration and diabetic
retinopathy.
LASEK (Laser Epithelial Keratomileusis)
Procedure that is similar to LASIK, except that the
surgeon cuts a flap in the epithelium only, instead
of through the epithelium and part of the stroma. LASEK
is used mostly for people with thin or flat corneas
who are poor candidates for LASIK, which requires more
corneal tissue for success.
LASIK (Laser-Assisted In
Situ Keratomileusis) Surgical procedure in which a tiny
flap is cut in the top of the cornea, underlying corneal
tissue is removed with an excimer laser, and the flap
is put back in place. LASIK corrects myopia and hyperopia.
lateral rectus muscle Muscle
that moves the eye away from the nose.
lens The nearly spherical
body in the eye that focuses light rays onto the retina.
limbus Boundary area connecting
the cornea and sclera; the three form the eye's outermost
layer.
lipid A fatlike substance
that can collect on contact lenses, making them uncomfortable.
low vision Also called partial
sight. Sight that cannot be satisfactorily corrected
with glasses, contacts, or surgery. Low vision usually
results from an eye disease such as glaucoma or macular
degeneration.
LTK (Laser Thermal Keratoplasty)
Also called Laser Thermokeratoplasty. Surgery to correct
mild farsightedness in people over 40; the doctor uses
a holmium laser to heat the cornea and shrink its collagen.
lutein An antioxidant that
is found throughout the body, but is concentrated in
the macula. Lutein is believed to help protect the eyes
from free radical damage caused by the sun's harmful
rays.
macula Part of the eye near
the middle of the retina; the macula allows us to see
objects with great detail.
maculopathy Disease of the
macula, such as age-related macular degeneration.
medial rectus muscle Muscle
that moves the eye toward the nose.
microcornea Abnormally small
cornea.
microkeratome Small instrument
that surgeons use to cut the cornea.
migraine (ocular) Visual
phenomena that may accompany a migraine headache or
that may occur without any headache. They include light
flashes, spots, wavy lines, flickers, zig-zagging lights,
semi-circular or crescent-shaped visual defects and
distortions of shapes.
monovision Vision correction
method for those with presbyopia in which one eye is
corrected for near vision and the other for far, either
through contact lenses or refractive surgery. Monovision
eliminates the need for reading glasses, but does have
some drawbacks, including decreased depth perception.
multifocal Type of spectacle
or contact lens design that includes more than one focal
area, such as bifocals or trifocals.
myasthenia gravis Autoimmune
disease sometimes related to thyroid conditions. Signs
are droopy eyelids or double vision that worsen toward
the end of the day.
myopia Also called nearsightedness.
Condition in which visual images come to a focus in
front of the retina, resulting in defective vision of
distant objects.
nearsightedness Also called
myopia. Condition in which visual images come to a focus
in front of the retina, resulting in defective vision
of distant objects.
neovascularization Abnormal
growth of new blood vessels, such as in an excessive
amount, or in tissue that normally does not contain
them.
nevus Also spelled naevus.
Brown pigmentation resembling freckle or mole on white
of the eye. More often found in dark-skinned people.
Sometimes malignant.
nickel Metallic element used
mainly in alloys. Many eyeglass frames are made of nickel
alloy, so people who are allergic should choose a hypoallergenic
substitute, such as titanium.
nose pad One of a pair of
pads, usually clear, that rest on either side of your
nose and help to support your glasses.
nystagmus Condition in which
the eye oscillates repeatedly.
OD (oculus dexter) Right
eye. Or, doctor of optometry.
ocular hypertension Condition
in which the intraocular pressure of the eye is elevated
above normal and which may lead to glaucoma.
ocular migraine Visual phenomena
that may accompany a migraine headache or that may occur
without any headache. They include light flashes, spots,
wavy lines, flickers, zig-zagging lights, semi-circular
or crescent-shaped visual defects and distortions of
shapes.
ophthalmologist A medical
doctor (M.D.) who specializes in the eye. Ophthalmologists
perform eye exams, treat disease, prescribe medication,
and perform surgery. They may also write prescriptions
for eyeglasses and contact lenses.
optician Opticians are not
doctors, but in some states they must complete training
and be licensed. And in some states they can become
certified, after special training, to fit contact lenses.
Most opticians sell and fit eyeglasses, sunglasses,
and specialty eyewear that are made to an optometrist's
or ophthalmologist's prescription. Many also have equipment
on the premises so they can grind lenses and put them
in frames without ordering from a lab.
optic nerve Part of the eye
that carries stimuli from the rods and cones to the
brain.
optic nerve head Also called
optic disk. Circular area where the optic nerve enters
the retina, and the location of the eye's blind spot.
optometrist Doctors of optometry
(O.D.s) examine eyes for both vision and health problems,
prescribe glasses, and fit contact lenses. They can
prescribe many ophthalmic medications and may participate
in your pre- and postoperative care if you have eye
surgery. O.D.s must complete four years of post-graduate
optometry school for their doctorate.
orthokeratology (ortho-k)
Procedure in which a doctor fits you with special gas
permeable contact lenses to reshape your cornea and
correct errors like nearsightedness. Often, patients
wear the lenses just at night.
OS (oculus sinister) Left
eye.
OU (oculus uterque, oculus
unitas or oculus uniter) Both eyes.
overconvergence Condition
in which the eyes come too far inward when focusing
on a near object, resulting in blurring.
papilla Small bump where
the optic nerve exits the eye.
pars plana Posterior part
of the eye's ciliary body.
peripheral vision The edges
of your visual field.
photoablation Procedure in
which a surgeon uses ultraviolet radiation to remove
tissue.
photochromic Able to change
lens color or darkness/density depending upon the degree
of exposure to light.
photokeratitis "Sunburn"
of the cornea; symptoms include discomfort, blurred
vision, and light sensitivity. The temporary vision
loss that can result is called "snow blindness."
pingueculum Yellowish, thickened
lesion on the conjunctiva. May be caused by irritation
from sun, dust and wind.
plano A term eyecare professionals
use to describe lenses with no corrective power. The
term is most often applied to nonprescription sunglasses
or contact lenses that are worn for cosmetic purposes
only.
PMMA (polymethyl methacrylate)
Old-fashioned hard contacts were made of PMMA, which
is not permeable; today's rigid lenses contain other
polymers that allow oxygen to reach your eye.
polarized lenses Lenses that
block light reflected from horizontal surfaces such
as water, to reduce glare.
polycarbonate Plastic that
is very impact-resistant, and is thus sometimes used
for spectacle lenses and frames.
posterior chamber Part of
the eye behind the iris and in front of the lens.
presbyope Person who has
difficulty reading print and seeing near objects.
presbyopia Inability of the
eye lens to focus incoming light, resulting in blurred
vision at a reading distance and eyestrain. Most people
develop presbyopia in their 40s.
prescription lenses Lenses
that provide vision correction as prescribed by an eyecare
practitioner.
PRK (Photorefractive Keratectomy)
Surgical procedure in which an excimer laser is used
to remove corneal tissue to correct vision problems.
progressive lenses (also,
progressive addition lenses or PALs) Multifocal lenses
whose corrective powers change progressively throughout
the lens. A wearer looks through one portion of the
lens for distance vision, another for intermediate vision,
and a third portion for reading or close work. Each
area is blended invisibly into the next, without the
lines that traditional bifocals or trifocals have.
propionate A soft, flexible
material that is sometimes used in goggles.
protective eyewear Eyewear
made with impact-resistant lenses, usually polycarbonate,
that protects the eyes, especially in working situations
or sports.
protein An organic substance
that can collect on contact lenses, resulting in discomfort
and cloudy vision.
pterygium Triangular-shaped
fold of tissue on white of the eye. May eventually grow
over part of the cornea. May be caused by irritation
from sun, dust and wind.
pupil The round, dark center
of the eye, which opens and closes to regulate the amount
of light the retina receives.
reading glasses (readers)
Glasses to help with close work, particularly for people
who are presbyopic.
refractive surgery Surgery
that corrects visual acuity, with the objective of reducing
or eliminating the need for glasses and contacts. Includes
radial keratotomy, PRK, LASIK, and corneal implants.
replacement schedule How
often you discard and replace your contact lenses: every
day, week or two weeks (disposable); or every month,
two months or calendar quarter (frequent replacement).
It's important to differentiate between replacement
schedule and wear schedule. Wear schedule is either
daily wear (removed before sleeping) or extended wear
(you may sleep with them in).
retina The sensory membrane
that lines the eye; it is composed of several layers
and functions as the immediate instrument of vision
by receiving images formed by the lens and converting
them into signals which reach the brain by way of the
optic nerve.
retinal detachment Condition
where the retina separates from the choroid.
retinitis pigmentosa Condition
characterized by the progressive loss of peripheral
vision, usually beginning with night blindness.
RGP (Rigid Gas Permeable)
Type of contact lens made of breathable plastic that
is custom-fit to the shape of the cornea. RGPs are the
successor to old-fashioned hard lenses, which are now
virtually obsolete.
rod A photosensitive receptor
in the retina that helps you to see in low light.
RK (Radial Keratotomy) Surgical
procedure where cuts are made in the cornea in a radial
pattern, to flatten the cornea and correct myopia.
sclera The outer coat of
the eyeball that forms the visible white of the eye
and surrounds the optic nerve at the back of the eyeball.
segment A part, as in the
near-vision portion of a pair of bifocals.
silicone Type of flexible
and comfortable plastic. Because it is commonly used
in nose pads in eyeglasses, people who are allergic
to silicone should ask their eye doctor for a different
type of nose pad.
soft contact lenses Contacts
made of gel-like plastic containing varying amounts
of water.
solution Product used to
clean, disinfect and store contact lenses.
SPF (sun protection factor)
Number representing the amount of sun something blocks.
For example, if you normally begin to burn after half
an hour in the sun, a sunscreen with an SPF of 2 should
let you stay out twice as long (1 hour), SPF 4 should
let you stay out four times as long, and so on.
spherical A contact lens
design that is like a sphere and is fairly common; in
contrast, toric lenses for astigmatism are football-shaped
and are less common.
spots Small, cloudy specks
in the eye that become noticeable when they fall in
the line of sight.
spring hinge Type of hinge
on eyeglass frames that is more flexible than a regular
hinge, making the frames more durable.
strabismus A misalignment
of the eyes: they don't point at the same object together.
Crossed eyes are one type of strabismus.
stroma The cornea's middle
layer; it consists of lamellae (collagen) and cells,
and makes up most of the cornea.
sty A blocked gland at the
edge of the lid which has become infected by bacteria.
suspensory ligament Also
called zonule of Zinn. Membrane of fibers (zonules)
that holds the eye's lens in place.
temple The "arm" of a pair
of glasses, running from the ear to the lens area.
titanium A type of metal
alloy that is very strong. Eyeglasses made of titanium
are lightweight, durable and often hypoallergenic.
toric A lens design with
two different optical powers at right angles to each
other for the correction of astigmatism.
trifocal A lens design that
has three focal areas: a lens for close work or reading,
a lens for mid-distance viewing or arm's length, and
a lens for faraway viewing or driving.
ultraviolet (UV) The invisible
part of the light spectrum whose rays have wavelengths
shorter than the violet end of the visible spectrum
and longer than X rays. UVA and UVB light are harmful
to your eyes and skin.
uvea Middle layer of the
eye, below the limbus, and consisting of the iris, ciliary
body and choroid.
uveitis Inflammation of the
uvea.
vitreous body Part of the
eye between the lens and the retina, containing a clear
jelly called the vitreous humor.
wear schedule How long you
wear your contact lenses: either daily wear (you remove
the lenses each night) or extended wear (you may sleep
with them in). It's important to differentiate between
wear schedule and replacement schedule — that
is, how often you discard and replace your lenses.
wraparound (wrap) Type of
eyeglass frame that curves around the head, from the
front to the side. Wraparound sunglasses tend to offer
extra sun protection because the lenses usually wrap
as well.
Discount
Contact Lens
|