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Glossary |
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Accommodation -
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The eyes ability to change focus from distant to near.
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Add -
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The power required for near (reading) vision.
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Ansisometropia -
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Very different refractive errors between the eyes.
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Antinetropia -
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One eye myopic (nearsighted) and one eye hyperopic (farsighted).
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Anti-Reflective (AR) Coating -
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A coating that is applied to both surfaces of the lens in
layers to reduce reflections. This coating allows more light
to be used by your eye for better vision. AR eliminates glare,
increases light transmissions, reduces eyestrain, increases night
vision and provides clearer cosmetically appealing lenses. A clear
lens without AR only allows around 90% of the light light to pass
through to the eye-this is why AR helps you to see better.
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Astigmatism -
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A condition in which the surface of the cornea is not
spherical causing a blurred image to be received at the retina. This
is reflected on a prescription as a cylinder (cyl) correction.
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Axis -
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An imaginary line at right angles to the surface of a
lens, which passes through the optical center. Also, the
meridian of zero power in a cylinder lens, perpendicular to
the meridian containing the maximum cylinder power.
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Base Curve -
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The surface curve of an ophthalmic lens that becomes the
base from which the remaining curves are measured. This is
a measurement in diopters.
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Bifocal -
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A lens with two powers; distance and near.
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Binocular Vision -
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The blending of the separate images seen by
each eye into a single image. Binocular vision
allows images to be seen with depth. Pertains to both eyes.
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Compound Lens -
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An ophthalmic lens that contains both a spherical
and cylindrical refractive power.
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Convex Lens -
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A spectacle lens that is thicker in the center
and thinner on the edges. A convex or plus lens
adds optical power to incoming light rays and is
used for the correction of hyperopia (farsightedness). This
is reflected on a prescription as + or positive power.
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Decentration -
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The displacement of the lens optical center from
the geometric center of the frame. A lens may be decentered
in order to align the optical center in front of the patient’s
pupils or displaced away from the pupil to create a prismatic effect.
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Diopter -
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A unit of measure of the refractive power of a lens.
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Diplopia -
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Double vision.
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Drill Mounted Frame -
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The lens are held in with brackets, plastic sleeves or screws
that are drilled through the lens. This is the popular “no frame” look.
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Drivewear Lenses -
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A unique lens category because it is the first lens
ever available that combines Transitions and Polarized
technology together. This lens will change inside a car because
it is activated by light instead of UV exposure, however this
lens does not get clear inside.
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Emmetropia -
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Normal eyesight.
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Full Frame -
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Any eyeglass frame that has metal or plastic completely
surrounding the lens.
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Full Frame -
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Any eyeglass frame that has metal or plastic completely
surrounding the lens.
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Glass -
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The original lens material, it is rigid, shatters easily. is
heavier but is more scratch resistant than other lens materials.
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Hi-Index Lenses -
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Thinner lens materials with inherent UV protection.
Cosmetically more attractive for prescriptions over + or – 2.00.
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Hyperopia -
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Farsightedness; the ability to see objects in the distance
clearly but not objects up close. May be corrected with eyeglasses.
This is reflected on a prescription as a plus or positive power(+).
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Lens Bev -
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The edge of a lens shaped like a V. The bevel is manufactured
to hold the lens in place inside a full frame.
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Lens Power -
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The power of a lens measured in diopters.
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Metal Frame -
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There are numerous “metals” that eyeglass frames
are made out of including stainless steel, titanium,
nickel, aluminum, monel and sometimes a combination of several metals.
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Monocular -
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Pertaining to one eye.
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Myopia -
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Nearsightedness; the ability to see objects up close
clearly but not objects in the distance. May be corrected with eyeglasses.
This is reflected on a prescription as a minus or negative power (-).
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Near Vision -
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Usually from about 11 inches to within arms reach.
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Normal Vision -
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When vision is clear while seeing in both distance and near.
The eye is able to focus images clearly on to the retina.
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O.D. -
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Right Eye.
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O.S. -
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Left eye; Latin meaning oculus sinister.
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O.U. -
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Both eyes;latin meaning oculus uterque.
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Ophthalmologist -
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A physician who specializes in the treatment of eye diseases,
conditions and eyesight correction. An ophthalmologist is
licensed to practice medical and surgical eye care.
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Optician -
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An eyecare professional trained to design and adapt eyewear
prescriptions for the specific wearer.
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Optometrist -
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A eye physician that conducts refractive examinations and assesses
overall eye health
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Peripheal Vision -
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The ability to see objects and movement outside the direct line of vision.
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Photochromic Lenses -
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Lenses that have the ability to change from clear (indoors) to dark
(outside) with exposure to UV light. These lenses do not change inside a
car. Blocks 100% UV light. This products is sold under trade names-Transitions,
Instashades, LifeRX, Sunsensors
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Plano -
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A lens without a refractive power.
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Plastic Frames -
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There are numerous types of plastic used to make eyeglass
frames including zyl (zylonite), cellulose proprionate, carbon,
nylon cellulose propionate, Kevlar® and optyl.
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Plastic Lenses -
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50% lighter weight than glass lenses, can be coated for
UV protection and scratch protection, may also be tinted many
colors.
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Polarized Lens -
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These lenses eliminate glare by absorbing sunlight and filtering
only useful light to the eye. 98% absorption of UV light.
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Polished Edges -
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This is a process that makes the lens edges clear rather than opaque.
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Polycarbonate Lenses -
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Impact resistant, lighter weight than plastic, 99% UV absorption,
and the recommended lens material for children’s and sports eyeglasses.
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Presbyopia -
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The gradual loss of the eyes ability to change focus from
distance to near vision; the loss of accommodation. This
condition is generally associated around the age of 40 for most people.
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Prescription -
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The formula needed to manufacture lenses so that the patient
can compensate for a refractive error.
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Prism -
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A transparent wedge shaped triangle used to bend light in the
direction of its base.
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Progressive -
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Lenses with varying optical powers that progress from the
upper part of the lens to the lower part with no lines that
provide more natural vision.
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Pupillary Distance -
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The distance between the center of one pupil to the other.
Used for the proper positioning of eyeglasses.
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Refraction -
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A test to determine a prescription to correct myopia, hyperopia,
astigmatism and presbyopia.
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Scratch Resistant Coating -
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A hard coating that is applied to the surface of the lens.
This product helps reduce scratching but does not guarantee that
the lens cannot be scratched.
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Segment -
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The insert portion of a bifocal or trifocal lens that contains
the plus power for near (reading) vision.
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Semi-Rimless Frame -
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A frame that can be either metal or plastic that does not
completely surround the lens. Generally the lens is held in at
the bottom of the frame with a monofilament line giving the appearance
of less frame.
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Single Vision -
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The power of the lens is the same throughout the entire lens.
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Tinting -
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A color that is applied to lenses with a dye that is absorbed
into a layer on the lenses. Most colors are available for a tint.
Some lens products cannot be tinted.
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Trifocal -
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A lens with three powers; distance, intermediate and near.
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Ultra Violet Light (UV)-
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Harmful radiation that is present all of the time, even on cloudy days.
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