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OPT 1155 - Opthalmic Lenses Vocabulary With Correct Answers!! Characteristics of a Plus Lens - ANSWER Converges parallel incident light rays has plus power thickest in center, thinnest at edgesHas real image Magnifies Images Against motionincreases effective power as it moves away from the eye
Characteristics of a Minus Lens -Minus power ANSWER Diverges parallel incident light rays Thickest at end, thinnest at center Virtual imagesShows motion decreases effective in power as it moves away from the eye Abbe Number - ANSWER ratio of the refractivity in air to the main dispersion Addition (ADD) -used for a fixed distance such as reading. ANSWER Dioptric power added to the distance prescription to be
Aspheric -optical performance, particularly for high refractive powers. ANSWER a non-spherical surface curvature commonly used to improve
Barium Glass -bifocal lenses. ANSWER Glass containing mostly barium oxides. Used in reading and
Base Curve -spherical lens or the marked minimum surface power of a semifinished toric lens. ANSWER manufacturer's marked or nominal surface of a semifinished
Bent Lens - ANSWER term to distinguish the form of curves lenses Bevel -the frame. ANSWER V-shaped ende ground of the preriphery of a lens to hold the lens in
Biconcave - ANSWER lens in which both surfaces are concave Biconvex - ANSWER lens in which both surfaces are convex Bifocal -other. ANSWER spectacle lens in which one area has more dioptric power than the
Blank -may be added to produce a multifocal lens. ANSWER basic lens substrate, to which segment/different refractive power
Blank Size -millimeters ANSWER terms to describe the size of a lens, measured by its diameter in
Center Thickness - ANSWER thickness of the lens at the major reference point Compound Lens - ANSWER Lens containing a sphere and cylinder Concave - ANSWER Surface that curves inside. Hollow and curved. Convex - ANSWER Surface that curves outside. Elevated and round
Focimeter -center, major reference point location and prism power given on an ophthalmic lens. ANSWER Instrument for determining vertex power, axis location, optical
Fram PD -of the other eye rim. ANSWER distance from the temporal edge of one eye rim to the nasal edge
Geometric Center (GC) - ANSWER Point lying midway of all meridians on a lens Hi-Lite Glass -titanate ANSWER Refractive lead-free glass containing a leas substitute called
Index of Refraction -velocity of light in a given medium. ANSWER ration of the velocity of light in one medium to the
Inset -the segment optical center. ANSWER setting of the bifocal segment to enable the customer to read through
Intermediate -correct vision ranges intermediate to distant and near objects. Referees to an ANSWER area in a trifocal lens or blank which has been designated to intermediate viewing distance of approximately 30 inches. Laminated Glass -sheet of plastic. ANSWER lens containing two pieces of glass separated by a thin
Lap - ANSWER cast iron tool used in the grinding and polishing of lens surface Lens -is curved. ANSWER Transparent medium bounded by two geometric surfaces, on of which
Lens Clock (Measure) - ANSWER Instrument used to measure the sagitta of a lens
curve and usually calibrated to express the measurement in dioptric toll surface power. Lenticular Lens -mm, ground to the prescription and attached to a plano carrier. ANSWER string powered lens which as a central areal usually 30-
Magnesium Fluoride -glass lenses. ANSWER A transparent mineral used in anti-reflection coating of
Magnification -real inverted image of larger area than the object. ANSWER property of some optical lenses or systems of projecting a
Major Reference Point -prescription requirements shall apply. ANSWER point on a lens at which specified distance
Marked Power -and back surfaces resulting from surfacing tools calibrated for an index 1.530. ANSWER power resulting from the algebraic combination of the front
Medium - ANSWER substance that transmits light Meniscus Lens -concave. ANSWER Crescent shaped lens, one side convex and the other
Meridian -surface at a specified point. When applied to a lens, may also be the plane that contains ANSWER line of intersection of a surface with a plane perpendicular to that the optical axis. Meridional Power -meridian. ANSWER refractive surface power of a lens measured in a specific
Minify - ANSWER reduce the apparent dimensions
Plano - ANSWER 0 dioptric power Plano Lens - ANSWER Has no refractive power Plus lens -dioptric power. It is thicker at the center than at the edge. ANSWER A lens that converges light to a real focus and has a positive
Prescription -examiner. ANSWER formula for lenses required by patients prescribed by the
Progressive Lens -viewing range in which the power changes continuously rather than discretely. ANSWER a lens designed to provide correction for more than one
Prism -plane/curved sides with a base, apex, and apical angle. ANSWER wedged shaped piece of glass/transparent material having
Prism Diopter -a ray or light by a prism or lens. ANSWER unit of measurement used to express the angle of deviation of
Radius of Curvature -surface curvature were drawn all the way around. ANSWER 1/2 the diameter of a circle that would be created if the
Segment -the major portion. ANSWER specified area of a multifocal lens having a different power from
Single Vision - ANSWER lens with one focus Segment Height -bottom in a finished pair of eyewear ANSWER distance from the top of the multifocal segment to the
Slab-Off -lens to eliminate vertical imbalance at the reading level. Also known as bi-centric ANSWER The placing of two different curvatures on the front surface of a grinding. Sphere - ANSWER lens that has the same power in all meridians. Toric -surface ANSWER lens having two curvature at right angles to each other on the same
Transmission - ANSWER passing of light waves through one medium into another Transparent -object can be seen through it. ANSWER pertaining to a medium having of transmitting light so that
Transposition -either plus or minus. ANSWER mathematical switching of one cylinder form to another,
Trifocal - ANSWER Lens with three focusing points (distance, intermediate, and near) Uncut -been edged for mounting in a frame. ANSWER A lens with finished optical surfaces on both sides but which has
