Amblyopia (am-blee-oh'-pee-ah): Also called "lazy eye" it
is a condition where an eye has reduced vision that is not correctable
with optical devices and exists without any detectable eye disease
or physical abnormality. Often associated with strabismus.
Aspheric: A type of bifocal lens in which the lens power changes
gradually, from the center to the periphery of the lens
Astigmatic Keratotomy (AK): A surgical procedure to correct astigmatism
by reshaping the cornea from an oval shape to a more spherical
shape. Best suited for those with minimal or moderate astigmatism.
Astigmatism: Astigmatism is characterized by an irregularly shaped
cornea that causes light images to focus on two separate points
in the eye, producing a distorted image. Symptoms range from visual
discomfort in mild cases, to severe blurring and distortion similar
to a reflection in a fun-house mirror.
Automated Lamellar Keratectomy (ALK): A new procedure for extremely
nearsighted patients, where only a small portion of the affected
cornea is transplanted with sections from the donor cornea.
Bifocal/multifocal contact lenses: Contact lenses with two or
more viewing zones, with part of the lens designed for seeing
distant objects and another part for seeing near objects.
Bifocal glasses: Lenses with two viewing zones, one on top for
viewing far objects and one at the bottom for viewing both near
objects. Traditional bifocal glasses are generally recognized
by a well-defined visible line separating the two viewing zones.
Cataract: A clouding of the crystalline lens within the eye,
causing reduced visual acuity. Cataracts can be surgically removed
and replaced with an intraocular lens implant to restore vision.
Color blindness: A condition where some people can see colors
but experience difficulty in distinguishing between some or all
colors. Technically ‘color blindness’ is an incorrect
term. The correct term is "color vision deficiency." Males
are affected more than women.
Contact lens: A thin plastic lens designed to fit over the cornea,
usually for the correction of refractive error.
Cornea: The transparent surface that covers the pupil and iris
and provides most of the eye's optical power.
Crystalline lens: The natural lens of the eye, a transparent
structure suspended behind the iris. Focuses light rays on the
retina and changes shape to change the focus of the eye for different
Daily wear contact lenses: Contact lenses designed to be worn
only during waking hours; removed, disinfected and stored for
the next day's use
Deposits: Accumulations of substances usually tear film components
(protein), mucus, lipid, inorganic and soilant on the contact
lens surface and/or in the lens material.
Depth perception: The ability to judge the relative distance
of objects and the spatial relationship of objects at different
Disinfecting solution: An agent that destroys surface bacteria
and microorganisms on contact lenses
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 either worn for a single day or, if they are also "extended
wear" lenses, up to seven days, depending on wear schedule
prescribed by the eyecare 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 under
the FDA definition.
Emmetropia: The condition generally known as "normal vision" where
light rays from distant objects are focused on the retina so that
vision is sharp and clear (20/20)
Extended wear contact lenses: Contact lenses designed to be worn
round-the-clock for intervals of one to seven days.
Farsightedness: See Hyperopia
Glaucoma: A condition where the pressure inside the eye is elevated
to a point that can damage the optic nerve and cause blindness
or a loss of peripheral vision.
Frequent & planned replacement contact lenses: General term
used to refer to contact lens regimens in which lenses are replaced
on a planned schedule, usually bi-weekly, monthly or quarterly.
Hyperopia (farsightedness): It is a visual defect where the light
rays focus behind the retina instead of on it due to flatter cornea
or shorter eyeball. People with hyperopia have difficulty seeing
objects close up.
Intraocular lens (IOL): Plastic lens implanted in place of the
crystalline lens (either behind cornea or behind the iris) during
Iris: The round, pigmented membrane surrounding the pupil of
the eye, having muscles that adjust the size of the pupil to regulate
the amount of light entering the eye
LASIK: Stands for laser-assisted in situ keratomileusis. LASIK
is a refractive laser eye surgery for correcting near and far
sightedness and astigmatism and reduce dependency on glasses or
Myopia (nearsightedness): It is a visual defect where the light
rays focus in front of the retina instead of on it due to steeper
cornea or longer eyeball. People with this condition can see nearby
objects clearly but distant objects appear blurred.
Ophthalmologist (MD): Medical doctors (MD or osteopath) uniquely
trained to diagnose and treat all disorders of the eye. An ophthalmologist
is trained in all aspects of eyecare--medical, surgical and optical.
Optician: A paramedical professional who manufactures and dispenses
eyeglasses and helps in the selection of frames. The optician
may also dispense and/or fit contact lenses, depending on individual
states' licensing practices.
Optometrist (OD): State-licensed health care professionals who
diagnose and treat eye health and vision problems. An OD can prescribe
glasses, contact lenses, engage in low vision rehabilitation and
vision therapy, have the authority to prescribe ophthalmic medications
and perform certain surgical procedures. Optometrists hold the
doctor of optometry (OD) degree.
Oxygen permeability: The amount of oxygen diffusing through a
given amount of lens material in a given amount of time, under
specified testing conditions
Presbyopia: A condition where the eye loses its ability to focus
with aging. A person with presbyopia experiences difficulty and
takes longer in switching between objects at different distances,
such as, between the road and the speedometer when driving a car.
Photorefractive Keratotomy (PRK): A type of laser eye surgery
used in some cases to correct near sightedness, far sightedness
and astigmatism by reshaping the cornea.
Radial Keratotomy (RK): A surgical procedure to decrease near
sightedness by making radial incisions on the eye surface with
a highly precise diamond blade, which flattens the cornea for
vision correction. Once very common, the surgery is now considered
the riskiest of all corrective eye surgeries.
Retina: The thin nerve tissue in the back of the eye. It transforms
the image received from the lens into electrical impulses that
are carried to the brain for interpretation.
Rigid gas permeable lenses or RGPs: RGPs consist of a durable
plastic that transmits oxygen. Because they don't contain water,
RGPs resist deposits and are not prone to harboring bacteria.
Saline solution: A sterile salt solution used in cleaning, rinsing,
and sometimes storing of contact lenses
Snellen chart: A standardized test chart introduced in 1862 by
Dutch ophthalmologist Hermann Snellen to measure visual acuity.
See visual acuity below.
Strabismus: The inability of one eye to obtain binocular vision
with the fellow eye; usually due to imbalance of the muscles of
Therapeutic contact lenses: 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.
Tonometry: A standard eye test that determines the fluid pressure
inside the eye. Elevated pressure is a possible sign of glaucoma.
Toric lenses: Contact lenses designed to correct astigmatism
by bearing two different optical powers at right angles to each
Visual acuity: A measure of how well a person sees. It is expressed
as a fraction (e.g. 20/20) where the numerator is the testing
distance and the denominator is the distance at which a person
with normal eyesight can read the letters on the chart. For example,
if the smallest letters that the person being tested can see are
on the "20/40" line, it means a person with normal eyesight
can see these same letters at a testing distance of 40 feet.