Glossary of Eye Care Terms.
While certainly not a complete eye care dictionary, the
EyeGlass Guide Glossary covers many of the common eye care conditions, terms and
technology you’ll commonly discuss with your eye care professional.
Amblyopia: Also called lazy eye.
Decreased vision in one eye that leads to the use of the other eye as the
dominant eye. A problem most commonly associated with children.
Anti-Reflective (A/R coating): A lens
treatment for your glasses that helps to reduce distracting glare and eye
fatigue by reducing the amount of light reflecting off the lens surface and
making the lenses appear clearer. Your eyes will also be more visible behind the
lenses.
Astigmatism: An eye condition where the
eye cannot focus light uniformly in all directions resulting from an irregular
curvature of the cornea, the crystalline lens, or the eye itself. It results in
mild to moderately blurred vision and/or eyestrain.
Bi-Focal Lenses: Lenses that use two
different distinct powers in each lens, usually for near and distance
correction.
Cataracts: A cataract is a clouding of
the crystalline lens of the eye that makes it hard for light to pass through and
be focused properly. In a normal eye, the crystalline lens is almost
transparent, however injury, age or disease can cause the lens to eventually
lose its clarity. When the lens becomes 'opaque,' it is called a cataract.
Treatable by surgery.
Color deficiency: A lack of ability to
distinguish certain colors. Commonly called “color blindness”, the most common
form of color deficiency is the inability to distinguish shades of red and
green.
Conjunctivitis (Pinkeye): An eye
condition caused by the inflammation of the conjunctiva, or clear membrane
covering the white part of the eye and lining of the eyelids. The eyes will
often appear swollen and red while also feeling gritty. It is often viral and
may be contagious. There are actually 20 different types of conjunctivitis –
from fairly common strains that usually pose no long-term danger to you or your
child's vision – to types that are resistant to antibiotics. Call or see your
doctor to treat pinkeye.
Cornea: The transparent, multi-layered
front part of the eye that covers the pupil and iris. It provides most of the
eye’s optical power.
Dry Eye Syndrome: An eye condition that
presents itself as itching, burning, and irritation of the eyes, is often called
"dry eye syndrome". It is one of the most common problems treated by eye care
professionals. It is usually caused by the breakdown (or deficiency) in the
tears that lubricate the eyes. As we age, our bodies produce less oil to seal
the eyes' watery layer. Hot, arid climates, air conditioning, certain medicines
and irritants such as cigarette smoke can all increase dryness of the eye. Your
eye care professional might prescribe "artificial tears" or other eye drops to
help alleviate the problem.
Floaters and Spots: A generalized term
used to describe small specks moving subtly but noticeably in your field of
vision. A floater or a spot is likely a tiny clump of gel or cells in the
vitreous – the clear, jelly-like fluid inside your eye. Aging, eye injury and
breakdown of the vitreous are the main causes of floaters and spots. If you
notice a sudden increase in the number you see, call your eye care professional.
Fovea: A tiny spot in the center of the
retina that contains only cone cells. This area is responsible for our sharpness
of vision.
Glaucoma: A common cause of preventable
vision loss when excessive pressure within the eye damages the optic nerve.
Treatable by prescription drugs or surgery.
High(er) Index: A dense lens material
that results in thinner, lightweight lenses than standard plastic. Index refers
to index refraction which is the speed that light travels through the lens.
Higher index lenses are available from 1.56 to 1.74 (the higher the number, the
thinner the lens). They are beneficial for stronger prescriptions.
Hyperopia: A condition where distant
objects are seen clearly, yet objects close up are seen less clearly. Also
commonly referred to as “farsighted.”
Iris: The pigmented (colored) membrane
that lies between the cornea and the crystalline lens that controls the size of
the pupil.
Crystalline Lens: The eye’s natural lens
located directly behind the iris. It has the ability to change shape to focus
light rays onto the retina.
Macula: The part of the retina
responsible for the sharp, central vision needed to read or drive.
Macular Degeneration: A group of
conditions that include a deterioration of the macula causing a loss of central
vision needed for sharp, clear eyesight. It is a leading cause of vision loss
and blindness in those 65 years of age and older. Macular Degeneration is also
called AMD or ARMD (age-related macular degeneration).
Minor Eye Irritation: Slight irritation
of the eye caused by a foreign body on the eye’s surface such as sand, dirt or
eyelashes. Wash your hands, then flush the eye with lukewarm water for up to 15
minutes. If the irritation remains and discomfort continues, seek professional
medical help immediately.
Multi-Focal Lenses: Multi-focal lenses
let you focus on two or more distances through the same lens (usually distance,
intermediate, and near). Also known as Bi-focals, Tri-focals, Multi-focals.
Myopia: A condition where distant objects
appear less clearly and those objects up close are seen clearly. Also commonly
referred to as “nearsighted.”
Nyctalopia: Commonly called “night
blindness,” this is a condition that presents as impaired vision in dim light or
darkness.
Optic Nerve: A bundle of nerve fibers
that carries messages from the eyes to the brain.
Photochromic lenses: Refers to lenses
that automatically change from clear to dark in the presence of ultraviolet (UV)
radiation.
Photophobia: Also called “light
sensitivity”, this is a condition that can have many underlying causes, and can
be prompted by many medications. Protection from bright light is critical for
anyone with this condition.
Plastic 1.50: This is a lens material
often used for minor prescriptions. Very few lenses are made from glass today,
since glass is heavier, thicker, and can shatter. Also referred to as standard
index or by the brand name CR-39.
Polarized lenses: This type of lens
includes an invisible “polarized” filter that helps to cut down on blinding
glare from reflective surfaces like water and snow for increased visual acuity
(sharpness) in bright light conditions.
Polycarbonate lenses: A lens material
that is thinner, lighter, and more impact resistant than standard plastic.
Polycarbonate lenses are the standard for children’s eyewear.
Presbyopia: Condition in which the aging
crystalline lens (at around age 40) becomes less able to change shape to focus
light at all distances, especially near vision. Can be corrected with reading
glasses, bifocals, or progressive lenses. Additional symptoms include eyestrain,
headaches, and squinting.
Progressives: Bi-focal or multi-focal
lenses with no visible lines where the lens power gradually changes from
distance to near. Also called PALs (Progressive Addition Lenses).
Pterygium: A raised growth on the eye
that is most often directly related to over-exposure to the sun. Dry, dusty
conditions may also contribute to development of these growths. Protecting your
eyes from UV radiation is a critical preventive measure.
Pupil: The opening in the center of the
iris that changes size to control how much light is entering the eye.
Pupillometer: An instrument used to
measure the distance between pupils. This measurement is used to position the
eyeglass prescription correctly in front of the eye.
Refraction: Test to determine an eye’s
refractive error and the best corrective lenses to be prescribed.
Retina: Part of the rear two-thirds of
the eye that converts images from the eye’s optical system into impulses that
are transferred by the optic nerve to the brain. Consists of layers that include
rods and cones.
Rods and cones: These are cells inside
the eye used by the retina to process light. Rods are used for low light levels
(night vision), cones are used for sharp visual acuity and color perception.
Sclera: The white part of the eye –
composed of fibrous tissue that protects the inner workings of the eye.
Single-Vision: Types of lenses that
correct one vision problem, like near or far-sightedness.
Snellen Chart: This is the commonly seen
eye care chart often topped by a large letter “E” used in eye examinations. This
measures your eye’s visual acuity, or the ability to see sharp detail clearly.
Strabismus: Sometimes called “crossed
eyes” in young children, this condition is the lack of coordination between the
eyes, such as one or both eyes turning in, out, up or down.
Ultraviolet radiation (UVR): Commonly
referred to as “UV Rays”, these are light waves that consist of both UVA and UVB
rays from the sun. Without proper protection, chronic exposure to UV rays can
lead to various eye conditions and damage.
UV Protection: Relates to a lens’ ability
to filter out harmful rays of the sun. It is recommended that glasses block 100%
of both UVA and UVB rays to minimize eye damage from the sun’s rays.
Visual Acuity: Assessment of the eye’s
ability to distinguish object details and shape – numerically expressed as
20/20, 20/70, etc.