Download Glossary of Terms Related to Ophthalmic Lenses and more Exams Advanced Education in PDF only on Docsity!
OPT 1 155 EXAM WITH CORRECT SOLUTIONS!!
Abbe Number (v) -dispersion. ANSWER It is the ratio of the refractivity in air to the main
Addition (ADD) -used for a fixed distance such as for reading. Commonly the dioptric power of the ANSWER The dioptric power added to the distance prescription to be bifocal segment. Aspheric -optical performance, particularly for high refractive powers. Such curvatures are often ANSWER A nonspherical surface curvature commonly used to improve derived from the oblique intersection of a plane and a conical surface and are referredto as "conoids" or conic sections.
Barium Glass -reading segments in bifocal lenses ANSWER Glass containing mostly barium oxides. Used primarily for the
Base Curve -spherical lens or the marked minimum surface power of a semifinished toric lens. A ANSWER A manufacturer's marked or nominal surface of a semifinished Semifinished lens of a given base curve may be part of a manufacturer's correctedcurve design series.
Bent Lens - ANSWER A term used to distinguish the form of curved lenses Bevel -in the frame. ANSWER The V-shaped edge ground on the periphery of a lens to hold the lens
Biconcave - ANSWER A lens in which both surfaces are concave Biconvex - ANSWER A lens in which both surfaces are convex
Bifocal -the other ANSWER A spectacle lens in which one area has more dioptric power than
Blank -power may be added to produce a multi-focal lens ANSWER The basic lens substrate, to which segment or different refractive
Blank size -diameter in millimeters ANSWER The term used to describe the size of a lens, measured by its
Center Thickness - ANSWER The thickness of a lens at the major reference point Compound Lens - ANSWER A lens containing a sphere and cylinder Concave -inside of a disc. ANSWER A surface that curves inside. Hollow and curved, such as the
Convex -of a disc. ANSWER A surface that curves outside. Elevated and rounded, as the outside
Corrective Curves -errors for the conditions of intended use over a specified portion of the field of view. The ANSWER A lens that has been designed to reduce spherical power use of different performance criteria may lead designers to different curvatures for agiven prescription. A group of lenses covering a range of prescriptions and based on the same performance criteria is referred to as a corrected curve series. Cross Curve -any cylindrical lens ANSWER The highest curve on either the front or the back surface of
Cylinder lens - ANSWER An ophthalmic lens in which one of its surfaces is cylindrical.
Hi-Lite Glass -titanate ANSWER A refractive lead-free glass containing a lead substitute called
Index of Refraction -velocity of light in a given medium, See also 'n'. ANSWER The ratio of the velocity of light in one medium to the
Inset -through the segment optical center ANSWER The setting of the bifocal segment to enable the customer to read
Intermediate -to correct vision ranges intermediate to distant and near objects. Refers to an ANSWER That area in a trifocal lens of blank which has been designed intermediate viewing distance of approximately 30 inches. Laminated Glass -sheet of plastic ANSWER A lens containing two pieces of glass separated by a thin
Lap - ANSWER A cast iron tool used in the grinding and polishing of lens surfaces. Lens -which is curved ANSWER A transparent medium bounded by two geometric surfaces, one of
Lensometer - ANSWER Same as Focimeter Lens Clock (Measure) -lens curve and usually calibrated to express the measurement in dioptric tool surface ANSWER An instrument designed to measure the sagitta of a power Lenticular lens -to 40 mm, ground to the prescription and attached to a Plano carrier. ANSWER A strong powered lens which has a central area usually 30
Magnesium Fluoride - ANSWER A transparent mineral used in anti-reflection coating of
glass lenses. Magnification -real inverted image of larger area than the object. ANSWER The property of some optical lenses or systems of projecting
Major Reference Point -prescription requirements shall apply (commonly but imprecisely referred to as the ANSWER That point on a lens at which specified distance optical center) Marked Power -front and back surfaces resulting from surfacing tools calibrated for an index 1.530 ANSWER The power resulting from the algebraic combination of the
Medium - ANSWER A substance that transmits light. Meniscus Lens -concave. ANSWER Crescent shaped lens. One side convex, the other side
Meridian -that surface at a specified point. When applied to a lens, it may also be defined as a ANSWER The line of intersection of a surface with a plane perpendicular to plane that contains the optical axis. Meridional Power -specified meridian. ANSWER The refractive or surface power of a lens measured in a
Minify - ANSWER To reduce the apparent dimensions. (The opposite of Magnify). Minus Cylinder - ANSWER A lens with two curvature on the back surface. Minus lens -thinner at the center than at the edge. ANSWER A lens that diverges light and has a negative dioptric power. It is
Plano - ANSWER Zero dioptric 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 -the examiner ANSWER The formula for lenses required by patient as prescribed by
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 -or curved sides with a base, apex, and apical angle. ANSWER A wedge shaped piece of glass or transparent material having plane
Prism Diopter -of a ray of light by a prism or lens. Prism power, in these units, is measured as the ANSWER A unit of measurement used to express the angle of deviation displacement of a ray. One prism diopter produces a deviation of I centimeter at adistance of 1 Meter.
Radius of Curvature -if the surface curvature were drawn all the way around. ANSWER One half the diameter of a circle that would be created
Segment -the major portion. This may also refer to the actual piece of material added to the lens in ANSWER A specified area of a multifocal lens having a different power from the case of a fused or cemented multifocal lens. Single Vision - ANSWER A lens with one focus Segment Height -bottom in a finished pair of eyewear. ANSWER The 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 -have rotationally symmetrical aspheric surfaces. ANSWER A lens that has the same power in all meridians. Such a lens may
Toric -same surface ANSWER A lens having two curvature at the right angles to each other on the
Transmission - ANSWER The 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 to minus to plus. ANSWER The mathematical switching of one cylinder form to another,
Trifocal - ANSWER A 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
Nominal Lens Power Formula - ANSWER F1+F2= F Total 1.523 Index - ANSWER Index of Refraction of Crown Glass Benjamin Franklin - ANSWER Invented bifocals Characteristic of Minus lens - ANSWER Diverge Light, Virtual Image, Thinner Center,
Cobalt Oxide - ANSWER Blue color Magnese Oxide - ANSWER Violet color Gold Oxide - ANSWER Red color Uranium Oxide - ANSWER Yellow Color Cerium Oxide - ANSWER Pink, or Brown color Iron Oxide - ANSWER Green Color Plastic (CR-39) - ANSWER Columbia Resin's 39th Formula, Plastic lens Polycarbonate lens -people ANSWER Better suited for Safety, Children, and Monocular
CR-39 Lens Characteristics -obtics, Clear white ANSWER 1.49 Index, safe, soft, Scratches easily, stable
Polycarbonate Lens Characteristics -scratches very easily, unstable optics, slight gray tone ANSWER 1.586 Index, Safest, very soft,
Striae -and stirring of raw materials ANSWER Fine streaks or veins in the glass itself-caused by insufficent mixing
Bubbles -nitrogen, carbon dioxide and monoxide, and other gases are formed. Stirring the ANSWER When new materials are being melted, bubbles of oxygen,
mixture with a clay rod eliminates bubbles and seeds. Stones -that didnt melt well, or pieces of clay pot that break away. ANSWER Foreign solids in finished glass. Caused by portions of raw materials
Milking or Fog -fog-resulting from reheating, molding or fusing. ANSWER Must be free from milkiness internally and surface
Strain -to anneal glass. Found on the outside edge of the lens ANSWER Caused by cooling new batch of glass too quickly. Takes 6 to 8 hours
Color -transparent in use. Must not discolor when exposed to sunlight. ANSWER Should be completely free of color. Must remain colorless and
Hardness -shatter under ordinary use. Must withstand impact from drop ball test, 15" drop ANSWER Must be tough enough to give good service and not scratch or
Expansion -different glass must have expansion qualities that are nearly identical, otherwise striae ANSWER Since different types of glass are fused to make bifocals, the will develop at t the lines of fusion. Therefore, the chemical compound of the glassesmust be comparable. It most go from melting point to cooling without breaking or cracking. Fog - ANSWER Glass must withstand heat up to fusion point and avoid fogging. Distortion -fusion of two pieces glass without softening enough to allow a change in curvature ANSWER The softening temperature must be to such a degree as to allow
index of refraction -for each type of glass, throughout the glass. ANSWER Must be maintained accurately within a very small range
F1 -CX) surface power ANSWER In Nominal lens formula- _________ (also called n1) is the front (usually
F2 -CC) surface power. ANSWER In Nominal lens formula- ___________ ( also called n2) is the back (usually
Base Curve +10 - ANSWER Fused Bifocal BC: Sphere Power +5.00 To +3. Base Curve +8.00 - ANSWER Fused Bifocal BC: Sphere Power +3.00 to +1. Base Curve +6.00 - ANSWER Fused Bifocal BC: Sphere Power +1.00 to +2. Base Curve +4.00 - ANSWER Fused Bifocal BC: Sphere Power -2.00 to -4. Base Curve Plano (+0.50) - ANSWER Fused Bifocal BC: Sphere Power Below -4. 186,000 miles per second - ANSWER The speed of light traveling through the air is
