Glossary of Optical Terms Compiled by Davis Vision
GLOSSARY OF OPTICAL TERMS
A-Lenses Colored or neutral lenses used to reduce dangerous visible and invisible radiation, or to reduce glare.
A-Dimension A measurement of the Boxing System that measures the distance between horizontal tangents to the bevel of a lens.
Abduction Divergence - The outward rotation of a pair of eyes in the attempt to maintain single binocular vision when stimulated by a base in prism or base in prisms.
Aberration An imperfection in a lens or optical system that prevents a point focus.
Ablepsia (A blep se ah) Blindness
Abrasion In contact lenses, scraping of the cornea due to ill-fitting lenses or over wearing of lenses.
Absorption The interception of radiant energy as it passes through a medium in which the energy is converted into heat, chemical energy or photoelectric energy. For example, ultraviolet light is converted into fluorescence or phosphorescence. Most optical, media have selective absorption, that is, absorb certain radiation (colors) differently.
Absorptive lenses Eyeglass lenses that absorb bright lights. Their purpose is to provide eye comfort against glare.
Access The brand name for Sola enhanced, near vision lenses. An access lens is a single vision reading lens with an enhanced range (extra close) at the bottom of the lens.
Accommodation The act of increasing the dioptric power of the eye by an increase in the power of the crystalline lens to permit objects at different distances to be clearly seen.
Accommodative Amplitude The total amount of dioptric power which the eye or eyes are increased by maximum effort of the ciliary muscle. The dioptric power increase of the near point over the dioptric power of the far point.
Page 1 Glossary of Optical Terms Compiled by Davis Vision Acrylic (ak krill lex) An economical lens material most commonly formed by the injection molding process. Lightweight and optically correct
Acuity Clearness, distinctness, sharpness of vision.
Addition (Add) Dioptric power added to distance prescription to supplement accommodation for some finite distance; such as reading. The dioptric power of a bifocal segment.
After-image phenomenon Ability of the eye to retain sight of an image during eye blinks.
Against motion Objects sighted through convex (plus) lenses move in an opposite (against) direction as the convex lenses are moved from side to side. See also with motion.
Age-related macular degeneration (AMD) An acquired retinal disorder characterized by degeneration in the central (macular) area of the retina. This is the leading cause of blindness in persons over age 65.
A-Scan Ultrasonography A noninvasive diagnostic test in which sound waves are used to determine the position of, and distances between, structures within the eye and orbit.
Amaurosis Blindness
Amblyopia (Am ble o pe ah) Low or reduced visual acuity not correctable. Amblyopia is said to exist if vision is uncorrectable to 20/30 or if vision in one eye is significantly less than that of the other.
Ametropia The refractive state of a static eye in which the secondary focus does not fall upon the retina.
Aniseikonia (An ih si ko neah) A relative difference in size and/or shape of the ocular images (right eye does not see an object the same size as the left eye).
Aniseikonic Lens A lens designed to correct the image size difference.
Anisocoria (An I so ko reah) Pupils of unequal size.
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Anisometropia (An I so me tro peah) A condition of unequal vision for two eyes.
Anomalies (A nom ah les) A deviation from the usual or norm.
ANSI American National Standards Institute- The organization which is responsible for setting all of the limitation, tolerances, and testing procedures that must be adhered to in many industries, including ophthalmic fabrication.
Anterior Close to the front.
Antimetropia One eye nearsighted; the other far- sighted.
AOA (American Optometric Association) The national, professional association representing optometry
Aphakia (A fa ke ah) Crystalline (clear lens behind eye) lens absent. Condition following cataract surgery.
A .R. Coat Anti-reflection lens coating. A clear coating that limits light reflection by allowing the maximum amount of light to pass through the lens. (E.g. Reflection-Free™)
Asthenopia A group of symptoms generally referred to as “eyestrain”. Included are: headaches, tearing, ”tired eyes,” itching, burning, and blurred vision.
Astigmatism (A stig mah tism) The eye is shaped like a football instead of a basketball, causes light rays to be distorted.
Associates Term used by Davis Vision, rather than employee, to refer to its work force. Associate refers to people working together towards a common goal.
Automated Field Measurement An examination to determine the viability of the nerve fiber layer of the retina and its effect on the field of vision of an individual.
Axis Degree at which eye power manifests it self.
Page 3 Glossary of Optical Terms Compiled by Davis Vision Axis, Cylinder That principal meridian which contains only the spherical power component of a sphero-cylinder lens.
Axis, Optical The straight line perpendicular to both faces of a lens along whose path a ray will pass without being deflected. It will intersect a spherical lens of a minus power at its thinnest point and a spherical lens of plus power at its thickest point. If the lens has prism power, the optical axis may lie outside the lens.
B-Dimension A measurement of the Boxing System which measures the distance between horizontal tangents to the bevel of a lens.
Back Order An order placed to fill a definite order from a dispenser. Also called short order, or special order.
Base The finished side of a semi-finished blank. The term refers to the curvature of the finished side. See Curve, Base.
Base- Apex line The line at a right angle to the refracting edge of a prim. The line on which an object appears to be displaced by refraction.
Base Curve The meridian of least curvature on a cylindrical surface. It may be found on either the convex or concave side of a meniscus lens.
Benchmarking An improvement process in which an organization measures its performance against that of best-in-class organizations, determines how those organization’s achieved their performance levels, and uses the information to improve its own performance. The subjects that can be benchmarked include strategies, operation, processes, and procedures. The objective of benchmarking is to identify and learn “best practices” and then to use those procedures to improve performance.
Bevel Apex The point of the bevel of a lens.
Bifocal (Bi fo kal) A lens containing two different powers one for distance, and one for near.
Bilateral (Bi lat er al) Both sides or both halves.
Bin Card A piece of paper or cardstock on which the inventory, sales and ordering of frames is recorded in the laboratory.
Binocular (Bin ok u lar) Use of both eyes simultaneously
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Biomicroscopy High magnification examination of the anterior segment of eye.
Blank, Molded A blank that is unfinished on both sides when it arrives from the factory. It is used to grind lenses for non-standard prescriptions or prescriptions that are particularly strong.
Blended Bifocal Lens containing two different posers, one for distance, and one for near. Segment with near prescription is invisible.
Blended Myodisc A lenticular lens used in the correction of high myopia, having a concave central corrective area 20 to 30mm in diameter, with a flat, non-corrective periphery.
Blepharitis (Blef ah ri tis) Inflammation of eyelid.
Blind Spot The area on the retina where the optic nerve enters. It is not sensitive to light since it has no visual receptors.
Blur point Where an object appears blurred either by moving it closer to the eye or by adding certain lenses or prisms until the test target blurs.
Boxing System A system of measurement used to define various prescription requirements relative to lens and frame dimensions.
Bridge The supportive structural member connecting the two eyes of an ophthalmic frame font.
Bridge, Keyhole A bridge design for a front that does not permit continuous contact between the nose and the front in the area of the nasal crest.
Bridge, Saddle A bridge design for a front that permits continuous contact between the nose and the front in the area of the nasal crest.
Bridge, Size The shortest horizontal distance between lenses (DBL), measured in millimeters.
BVI (Better Vision Institute) An organization dedicated to the preservation of sight through community education and public awareness.
Page 5 Glossary of Optical Terms Compiled by Davis Vision Canthus The point at which the upper and lower lids of the eye meet to form an angle. Inner c. junction point nearer to the nose. Outer c. junction point nearer to the temples
Carrier Number Used to uniquely identify the billing party of a Plan. The billing party may have multiple Plans and therefore multiple Client Control Numbers, e.g., Blue Cross might have a Carrier Number of 101 & 3 Plans: Plan A with a Client Control Number of 90 Plan B with a Client Control Number of 91 Plan C with a Client Control Number of 92, so A C# of 101 and CC#’s of 90, 91, and 92 are all related to Blue Cross
Case Harden Heat treatment of a glass lens for impact resistance.
Cataract (Kat ah rakt) Partial or complete loss of transparency of the crystalline lens. Clouded lens is removed by surgery and usually replaced with plastic lens called Intraocular lens implant.
Cellulose Acetate A thermoplastic which is not easily flammable. It is used as the material for spectacle frames. Safety plastic.
Cellulose Nitrate A highly flammable thermoplastic, which was formerly used as the material for spectacle, frames. Also known as celluloid, xylonite or zylonite. Also zyl.
Center A point on the axis of a lens between the nodal points through which extra-axial rays pass undeviated.
Center, Geometric The intersection of the horizontal and vertical centerlines of a box that circumscribes the lens shape.
Center, Optical One of the intersection points of the optical axis of a lens with the lens surfaces. It is the point at which the lens has NO prism power. Pure cylinder lenses have no well-defined center point since they have no power, and therefore no prism, in one direction.
Chemical Harden Chemical treatment of a glass lens for impact resistance.
Choroid The highly vascular middle coat of the eye globe lying between the sclera and retina. Its principal function is blood supply to sustain the retina.
Page 6 Glossary of Optical Terms Compiled by Davis Vision Chromatic Aberration The dispersion of colors arising from unequal refraction of light of the different wavelengths of the spectrum. This defect of an optical system causes the image to be surrounded by a halo of colors. It is corrected in an achromatic lens system.
Ciliary Body An extension of the uvea which is comprised of the ciliary muscle and ciliary processes. Its function is to assist in the changing of the crystalline lens in the act of accommodation
Ciliary Muscle The eye’s focusing muscle that allows the crystalline lens to perform its function of accommodation.
Cilium Eyelash. Cilia Eyelashes.
Coat Process of dipping lens into liquid dye or anti-scratch substance.
Color Blindness, Color Deficiency. Inability to recognize colors. Modern terminology prefers ”color deficiency” rather than “color blindness.”
Color Test Simple test done for color deficiencies. Book with red and green dots mixed together. If color deficient, it would look the same. If not, letters or numbers stand out in red or green.
Comprehensive Eye Examination It describes a level of service in which a general evaluation of the complete visual system is made. The comprehensive services constitute a single service entity but need not be performed at one session. The service includes history, general medical observation, external and ophthalmoscopic examination, gross visual fields and basic sensorimotor examination. It often includes, as indicated, biomicroscopy, examination with cycloplegia or mydriasis and tonometry. It always includes initiation of diagnostic and treatment program as indicated.
Cones Light-sensitive cells densely congregated in the central portion of the retina. They account for precise seeing and function at higher levels of illumination than the other light receptors, the rods. Color vision is a function of the cones.
Conjunctiva The transparent membrane lining the inside surfaces of the eyelids and the front surface of the eyeball (cornea).
Conjunctivitis (kon junk tih vi tis) Pink eye (Inflammation of the conjunctiva.).
Contact Lens A small shell-like lens that rests directly on the eye. There are many styles: Soft Lens – Lenses made from flexible water absorbent plastics. These lenses are comfortable at the end of the day.
Page 7 Glossary of Optical Terms Compiled by Davis Vision Daily Wear – Lenses put in the eye at the beginning of the day and removed at the end of the day.
Disposable/Planned Replacement – Soft lenses that are worn for a prescribed length of time, then are discarded. Compared to conventional soft lenses, these lenses offer the patient better eye health, clearer vision, increased comfort, and a “fresh lens feeling” on a continuous basis. There is very little to no maintenance involved with these lenses.
Extended Wear - A soft lens with the same comfort as a daily wear soft lens, but can be left in the eye for up to two weeks. Also tears easily.
Gas Permeable - A hard lens that is very oxygen soluble and quite comfortable to wear. They need minimal care and last for years.
Hard - One of the first contact lenses. Made of hard plastic. Generally not as comfortable, as soft or gas permeable lenses.
Medically Necessary – Contact lenses prescribed for conditions where visual acuity can not be adequately corrected with eyeglasses but can be corrected by contact lenses.
Monovision – A contact lens fitting technique used to correct presbyopia. The dominant eye is used for distance vision, while the weaker eye is used to see close up.
Scleral Shell – A contact lens that fits over both the cornea and the surrounding sclera (i.e., the “white of the eye).
Toric - A contact lens of specific design to correct astigmatism. Toric lenses may be made of soft or rigid materials. They are curved in a way that compensates for the irregular shaped cornea.
Convergence The movement of the eyes in which the internal recti turn the visual axes to intersect at some finite point.
Cornea Transparent portion of eye in front of the iris (colored part).
CPT (Current Procedural Terminology) A standardized mechanism of reporting services using numeric codes as established and updated annually by the AMA. A manual that assigns five digit codes to medical services and procedures to standardize claims processing and data analysis. The coding system for physicians’ services developed by the CPT Editorial Panel of the American Medical Association; basis of the Medicare coding system for physicians services.
Crystalline Lens The biconvex lens situated behind the iris of the eye. It is suspended from the ciliary body by a yoke of zonular fibers. By the force of the muscle fibers surrounding the lens its center thickness increases, its diameter decreases and the anterior portion bulges forward. This increases its dioptric power to focus the eye upon objects near to the eye. This act is known as accommodation.
Page 8 Glossary of Optical Terms Compiled by Davis Vision Curve, Base A manufacturer’s marked or nominal surface power of a semi-finished spherical lens or the marked minimum surface power of a semi-finished toric lens. A semi-finished or finished lens of a given base curve may be a part of a manufacture’s corrected curve design series.
Curve, Cross The maximum surface power of a toric surface (90 degrees from the base curve meridian).
Cyl or Cylinder Corrects astigmatism by bending light to compensate for uneven curvature of eye.
DBC Abbreviation for “Distance Between Centers.”
DBL Abbreviation for “Distance Between Lenses.”
Datum Line A line at the midpoint and parallel to the horizontal tangents to the top and bottom of a lens. The 180-line. The x-axis of a lens through the geometric center of the lens.
Decentration The act of placing the optical axis of a lens in a different position than the geometric center of a spectacle lens. The unit of measurement of the displacement is prism diopters. Lens power in diopters times decentration in centimeters equals prism diopters.
Depth Perception Perception of the relief of objects in which they appear as solids and not as flat pictures. Third-degree fusion.
Deuteranopia (Du ter ah no pe ah) Green color blind (not common).
Diabetes Mellitus Diabetes Mellitus affects approximately 18.2 million people in the United States. Diabetic eye disease can result in retinopathy, macular edema, glaucoma and/or cataracts. Diabetic retinopathy is the most common form of diabetic eye disease. It is the leading cause of blindness among people aged 20-44 and the second leading cause among people aged 45-74. Diabetes-relate blindness could be decreased by 45% with early intervention.
Diagnostic Pharmaceutical Agents (DPA) Topical drugs (eye drops) used by optometrists for diagnostic testing during an examination.
Diagnostic Pharmaceutical Authority (DPA) The level of certification of optometrists licensed to use diagnostic pharmaceutical agents.
Page 9 Glossary of Optical Terms Compiled by Davis Vision Didymium (die - dim - e - um) Didymium is used by commercial and artistic glass blowers where yellow light filtering is desired. This glass must be as least 3.0 mm thick in order to filter the yellow flare portion of the spectrum properly. The lenses should be mounted in a Z87 frame.
Dilated Examination (Dilation) The enlargement of the pupil by the application of diagnostic drugs in the form of eye drops. The larger pupil opening allows more detailed inspection of the peripheral retina to facilitate diagnosis and documentation of numerous potential diseases or disorders.
Dilation The opening of or enlarging of the pupil by means of eye drops, to better see inside the eye.
Diopter (Di op ter) Unit, which describes the power of spectacle, lenses.
Diplopia Double vision.
Distometer A device to measure the distance from the corneal apex to the pole (vertex) of a lens, the vertex distance.
Divergence Simultaneous turning out of both eyes to keep sight of an object as it moves farther from the eyes.
Dominant Eye The eye that ”leads” its mate during eye movements.
Double Seg A multifocal spectacle lens for occupational use, with near power segments inserted at both the top and bottom of the lens.
DPA Stands for Diagnostic Pharmaceutical Agents. A term used by eye doctors for eye drops used for diagnostic purposes during and eye examination.
Drop Ball Test A test that is performed on all glass lenses after they have undergone a chemical hardening process. This test involves dropping a half-inch steel ball on a lens from a height of 50 inches to test for impact resistance.
Dyslexia (Dis lek se ah) Impairment of the ability to read.
Edging The process of cutting a lens blank to the appropriate size and shape required for a particular frame.
Page 10 Glossary of Optical Terms Compiled by Davis Vision
Edge Polish A cosmetic procedure to give the outer edge of a finished spectacle lens a smooth, glossy appearance.
Edge Treatment Any of several processes that modify the appearance of the edge of a spectacle lens for cosmetic and/or functional purposes. These treatments include edge coating, edge polishing, and faceted edges. Cosmetically, edge treatments can stylize or add color to a normally plain edge. Functionally, they can reduce edge thickness or minimize internal reflections.
Emmetropia The state of an eye without refractive error in which visual acuity is at maximum for distant vision without accommodative effort.
Esotropic (Es o trop ik) The inward turning of an eye
Executive Bifocal Bifocal in which the near (reading) portion is across the entire bottom of lens. Useful for extended near work at a desk. (i.e., bookkeeper).
Exophoria (Ex o fo’ re ah) Tendency of the eyes to turn out.
Extraocular Muscles The six muscles which cause movement of the eye; internal and external recti and superior and inferior recti and superior and inferior oblique.
Eye The sense organ that contributes to the sense of vision.
Eye, Emmetrophic Another name for the normal eye, one that does not need corrective lenses.
Eye, Hyperopic Farsighted eye, cannot focus on objects that are close up. This eye may be thought of as optically shorter than it should be.
Eye, Left The aperture in front of the wearer’s left eye, as worn.
Eye, Myopic Nearsighted eye, unable to focus well on items that are in the distance.
Eye, Right The aperture in front of the wearer’s right eye, as worn.
Page 11 Glossary of Optical Terms Compiled by Davis Vision
Eyeglasses A term commonly used to describe an ophthalmic frame with lenses inserted.
Eyewire The component of an ophthalmic frame front, which encircles one lens. Also called an eye.
Faceted Lens A spectacle lens that has been cut and finished to give the periphery of the lens a jewel-like beveled appearance.
Far Point A point, which is conjugate with the macula, when accommodation is relaxed. In myopia it is less than infinity (6 meters0. In hyperopia it is a virtual point behind the retina.
Farsightedness A common term for hyperopia
Fashion Eye Consultants Assist patients in the selection of frames. Fill out frame related fields on the patient’s invoice(s).
Filtration Angle The angle formed by the cornea meeting the iris.
Flat-Top A type of multifocal, in which the segment is flattened at the top.
Flint Glass A glass with high refractive index containing lead.
Floaters Small spots floating (normal). Common complaint, “I see little black spots floating around”.
Flowchart A graphical representation of the steps in a process. Flowcharts are drawn to better understand processes. The flowchart is one of the seven tools of quality.
Focimeter An instrument used to determine vertex power, axis location, optical center, and major reference point location and prism power at a given point on an ophthalmic lens.
Former See Lens, Pattern.
Focus A point through which rays of light converge or from which rays of light appear to diverge when entering or emerging from an optical system.
Page 12 Glossary of Optical Terms Compiled by Davis Vision
Frame Plastic or metal structure for holding lenses.
Frame, Combination A frame whose front consists of a metal chassis with attached trim parts (sometimes known as top rims). These trim parts are typically plastic, aluminum or other metal, and are attached to the top portion of the chassis. These top rims may serve functional or cosmetic purposes, or both.
Frame, Dress Ophthalmic A frame for prescription or corrective lenses, intended for ordinary use in correcting or improving vision. Such a frame is not intended for occupational of safety use.
Frame, Rimless A type of frame that provides no, or only partial, peripheral support for the lenses.
Frame, Zyl A frame made from cellulose acetate.
Frames A book that is published quarterly with every frame manufactured and a price list that all doctors use to establish UCR for frames.
Front A component of an ophthalmic frame typically consisting of a bridge and eyewires.
Full Spectrum Lens An ophthalmic lens made from a plastic that transmits approximately 90% of ultraviolet light, whereas a conventional plastic transmits only 10%.
Fundus, Fundus Oculi Back portion of the eye that includes the retina, optic nerve and other sensitive elements responsible for sight.
Fusion Using both eyes together (normal when both eyes work together).
Glasses Colloquial name for eyewear.
Glaucoma (Glaw ko mah) Pressure of eye is too high. When pressure gets too high, it blocks circulation to retina and the retinal tissue, resulting in a loss of field of vision and in severe cases, blindness. Usually controlled by eye drops. Laser treatment sometimes necessary when eye drops fail.
Glazed Assembled with appropriate ophthalmic lenses.
Page 13 Glossary of Optical Terms Compiled by Davis Vision
Gonioscope (Go ne os skop) Instrument used to measure the filtration angle in the anterior chamber of the eye. Test for glaucoma if the eye pressure is high.
Gonioscopy (Go ne os ko pe) Observation of the filtration angle of the anterior changer with the Gonioscope.
Gradient Coat A lens coating that is darker at the top of the lens, fading to light at bottom.
Groove, Eyewire The recessed area of an eyewire in which the lens edge is seated, also called the lens groove.
High Index/High Lite Material that results in thinner (almost one third less) lenses than normal plastic. Does not contain the impact resistant qualities of Polycarbonate.
Hinges Part of the hardware of the frame. The hinges attach to both the temple and front of the frame.
Histogram A graphic summary of variation in a set of data. The pictorial nature of the histogram lets people see patterns that are difficult to see in a simple table of numbers. The histogram is one of the seven tools of quality.
Horizontal Meridian The 180-degree meridian in cylindrical surfaces.
Hyperopia (Hi per o pe ah) Farsighted (difficulty seeing up close).
Hyperphoria (Hi per fo re ah) Tendency of one eye to deviate upward.
Hypertropia An actual deviation of the z-axes in the vertical meridian.
Hypophoria Vertical heterophora in which one eye tends to deviate downwards relative to the other. This can be differentiated from Hyperphoria in the other eye only by evidence of paresis or paralysis of elevating.
Index of Refraction The ratio of light velocity in one medium, to the velocity of light in the next medium.
Page 14 Glossary of Optical Terms Compiled by Davis Vision Infinity A distance, which is great as, compared with the aperture of focal length of an optical system. Six miters (20 feet) the distance used for refraction is over 1000 times the width of the pupil and about 400 times the focal length of the eye. At 6 meters the size of the pupil subtends an angle of less than 4 seconds at the first nodal point.
Intermediate That area in a trifocal lens or blank which has been designed to correct vision at ranges intermediate to distant and near objects.
Intermediate examination Describes a level of service pertaining to the evaluation of a new or existing condition complicated with a new diagnostic or management problem. This does not necessarily relate to the primary diagnosis, including history, general medical observation, external ocular and adnexal examination and other diagnostic procedures as indicated; may include the use of mydriasis.
Intraocular Within the eye.
Iris Colored part of eye.
Iritis (I ri tis) Inflammation of the iris.
Jaeger Test Measurement of visual acuity at the reading distance.
Keratometer An instrument used to measure the curvature of small areas of the cornea by reflected light.
Kerititis (Ker ah ti tis) Inflamed cornea.
Keratoconus (Ker ah to ko nus) Cornea gets progressively steeper (Cone shape). May be fit with a hard contact lens to slow progression. Surgery may eventually be necessary (cause unknown).
Lead Glass Optical glass containing lead oxide. High-refractive index promotes its use for fused bifocal segments. Its high- chromatic aberration (low v-value) makes it objectionable. Syn. Flint glass.
Leadership Index A table of key statistics monitored by Davis Vision which indicates the level of success achieved, in instilling the company’s quality values throughout the organization.
Page 15 Glossary of Optical Terms Compiled by Davis Vision Lens A transparent medium bounded by two geometrically describable surfaces one of which shall be curved – that is, spherical, cylindrical, toroidal or aspheric.
Lens, Bifocal A lens designed to provide correction for two viewing ranges.
Lens, Concave See Lens, Minus
Lens, Converging See Lens, Plus
Lens, Convex See Lens, Plus
Lens, Corrected Curve A lens that has been designed to reduce peripheral power errors for the conditions of intended use over a specified portion of the field of view.
Lens, Cylinder A special case of the sphero-cylinder lens in which one of the principal meridians has zero refractive power.
Lens, Diverging See Lens, Minus
Lens, Edged A lens whose periphery has been ground (flat, beveled or grooved) to a specific size and shape.
Lens, Fused A mutli-focal lens made from three or more pieces of glass which are thermally sealed together. On fused multi-focal lenses
Lens, Laminated All multiple layers of glass or plastic, or both, bonded together to form a single unit
Lens, Lenticular A lens, usually of strong refractive power, in which the prescribed power is provided over only a limited central region of the lens, called the lenticular portion. The remainder of the lens is called the carrier and provides no refractive correction but gives dimension to the lens to allow for mounting in a spectacle frame.
Lens, Measure An instrument that is used to measure surface curvature. Also called sagitta gauge, or lens clock.
Lens, Minus A lens having negative dioptric power. It is thinner at the center than at the edge.
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Lens, Multifocal A lens designed for two or more viewing ranges, for example, bifocal or trifocal lenses.
Lens, One-Piece Multifocal A multi-focal lens or a blank fabricated from a single piece of glass or plastic
Lens, Pattern A cam , or template, used in lens edging equipment to generate the correct peripheral shape and geometric center location. Also called a lens former.
Lens, Photochromic A lens that darkens in response to the ultraviolet component of sunlight.
Lens, Plano A lens which has zero refractive power.
Lens, Plus A lens that has positive refractive power. It is thicker at the center than at the edge.
Lens, Progressive Power A lens that is designed to provide correction for more than one viewing range in which the power changes continuously rather than discretely.
Lens, Semi-Finished A lens that has only one surface finished.
Lens, Single – Vision A lens designed to provide correction for a single viewing distance.
Lens Size The horizontal box dimension (A-dimension) of a finished lens. Also called eye size.
Lens, Spherical A lens that that has the same refractive power in all meridians. Such a lens may have rotationally symmetrical aspheric surfaces.
Lens, Sphero-Cylinder A lens that has different refractive power in the two principal meridians. It is sometimes referred to as an astigmatic or toric lens. It is sometimes INCORRECTLY referred to as a cylinder lens.
Lens, Stock Factory Finished Uncut A lens supplied by a manufacturer with both surfaces finished and a specific back vertex power or powers. Such a lens has yet to be edged to a specific shape.
Page 17 Glossary of Optical Terms Compiled by Davis Vision Lens, Toric A lens which has two distinct curvatures, at right angles (90 degrees) to each other. See Lens, sphero-cylinder.
Lens, Uncut A lens with finished optical surfaces on both sides but not edged for mounting in a frame.
Lensometer (Lenz om eh ter) Instrument which can measure the power of a spectacle lens.
Lenticular Lens See Lens, Lenticular
Light A form of energy necessary to see. Visible light is that part of the spectrum that produces sensation of sight in the human eye. The wavelengths of the radiation in this visible range are very small and are usually expressed in either millimicrons or nanometers. The values given for the limits of the range of wavelengths in visible light will depend on the textbook you are reading, but will be around 380 – 760 nanometers or 400 –750 nanometers. The rays that cause us to see violet have the smaller, shorter wavelength, around 380 nanometers or millimicrons. Each color of the spectrum, blue, green, yellow, and orange, will have a range of wavelengths up to red at around 660 –750 nanometers.
Limbus The circular zone where the cornea joins the sclera (white of the eye).
Linel Geometric A horizontal line running through the geometric center of a lens. Also called normal mounting line.
Loupe A binocular magnifier in which the lens axes are inclined on the fixation axes or a magnifier which uses Base In prisms to relieve convergence along with the accommodation relieved by plus lenses.
Low Power Aspheric A lens in which one or both surfaces do not conform to a sphere, allowing systematic variations in optical characteristics from the center to the periphery of the lens, so designed to correct for or reduce certain types of aberrations.
Macula The point of clearest vision at the center of the retina.
Magnification The property of some optical lenses or systems of projecting a real inverted image of larger area than the object.
Major Reference Point The point on a lens at which the specified distance prescription requirements shall apply (commonly but imprecisely referred to as the optical center).
Page 18 Glossary of Optical Terms Compiled by Davis Vision Mechanical Center The geometric center of an optical lens.
Medium A substance that transmits light.
Members The end user of Davis Vision’s products and services the patient.
Meniscus Lens A lens with a profile similar to a crescent, one surface convex, the other concave.
Meridian A lens plane perpendicular to the optical axis of a lens or optical system. A diameter of a round or oval lens.
Meridians, Principal The two mutually perpendicular meridians of a sphero-cylinder lens or toric optical surface with minimum and maximum power.
Migraine Type of headache that usually occurs on one side of the head and is accompanied by visual disturbances, such as sparkles and spots before the eyes.
Minify To reduce the apparent dimensions. The opposites of magnify.
Millimeter (Mil ih me ter) Metric system of measurement. 25.4mm equals 1 inch (used for measuring bifocals, frames, lenses, pupillary distance, etc.).
Mirror Coating A thin deposit of appropriate material to the front surface of a lens causing a portion of the light striking the lens to reflect directly from the front surface.
Monocular Refers to only one eye. One side of a prism binocular.
Monovision A procedure for correcting presbyopia with contact lenses. a contact lens of appropriate power to correct near vision is fit on the other eye. This allows clear vision at both distance and near to be achieved, though binocular coordination and depth perception may be affected in some persons.
MRP (Materials Review Program) The quality assurance program performed by the RQARs. The frame collection is audited for removal of discontinued styles, and replacement of missing frames. Additionally, information on current and future clients is provided and the visit is an effective feedback mechanism.
Page 19 Glossary of Optical Terms Compiled by Davis Vision
Multifocal A lens having more than one focal power in USA. A lens having more than two focal powers in UK.
Myopia (Mi o pe ah) Nearsighted (difficulty seeing at distances).
Near Point The closest point at which accommodation can be momentarily maintained. Punctum proximum, (PP).
Nearsightedness A condition that usually starts in childhood and stabilizes in the late teens or early twenties. Because the eye’s focusing powers are too strong for the size of the eye, near objects are seen more clearly and those far away appear blurry. Light is focused in front of the retina (Myopia).
Nodal Points Two of the cardinal of Gaussian geometric optics that coincides with the principal points when the first and last mediums have the same refractive index. When an object ray is directed toward the first nodal point, it emerges without deviation into the image space from the second nodal point.
Normal The perpendicular to a surface at the point of incidence of a ray. It is the extension of a radius of a spherical surface at the point of incidence.
Nystagmus (Nis tag mus) Involuntary movement of eyes. Muscle integrity as well as neurologic and systemic causes possible.
Occluder A device that excludes light from one or both eyes.
Oculus Dexter (OD) Term used by practitioners to refer to the right eye.
Oculus Sinister (OS) Term used by practitioners to refer to the left eye.
Oculus Uterque (OU) Term used by practitioners to refer to both eyes.
Ocular 1. An eyepiece. 2. Pertaining to the eye.
OD Latin abbreviation meaning right eye. Ocular Dexter.
Page 20 Glossary of Optical Terms Compiled by Davis Vision OLA(Optical Manufacturers Association Trade organization for wholesale laboratories.
OMA(Optical Manufacturers Association) Trade organization for the manufacturers of ophthalmic frames and lenses.
Opacity The change in a material from being transparent to being non-transparent.
Ophthalmic With reference to the eye and its functions.
Ophthalmologist (Op thal mol o gist) A medical doctor who has completed a residency program in ophthalmology and specializes in vision care that is related to medical conditions, such as, treating diseases of the eye and performing ocular surgery. "Title" is M. D.
Ophthalmoscope (Op thal mo skop) Instrument used to examine internal health of the eye.
Ophthalmoscopy Test for internal health of the eye.
Optic Pertaining to light or the sense of sight.
Optic Nerve (Op tik) Carries nerve impulses from eye to brain.
Optical Axis The line connecting the centers of curvature of a lens or system of lenses. The cardinal points lie on this line or its extensions. The anterior-posterior axis of the eye.
Optical Center A point on the lens axis midway between the nodal points.
Optician A fabricator and dispenser of eyeglasses. Some opticians also fit contact lenses. An optician is skilled in the application of the science of optic, including optical lens and/or instrument designing or manufacturing.
Optometrist A doctor of optometry providing all ophthalmic services except surgery. In most states they are licensed to treat ocular diseases. "Title " is O.D.
Page 21 Glossary of Optical Terms Compiled by Davis Vision Organization Culture A system of values, beliefs, and behaviors inherent in an organization. To optimize performance, leaders must define and create the necessary culture. Davis Vision s culture is: “Do Whatever It Takes!”.
Orthoptic Training A method of correcting defective vision such as strabismus or accommodative-convergence imbalance by stereoscopic and other ocular exercises.
OS Latin abbreviation meaning left eye. Ocular Sinister
Otolaryngology The branch of medicine that deals with diagnosis and treatment of diseases of the ear, nose, and throat. Also called otorhinolaryngology.1
OU Latin abbreviation meaning both eyes. Ocular Uterque
Oversize A larger than standard lens is required to fabricate eyeglasses.
Ozone Ozone (03) is a gas which has chemical properties similar to hydrogen peroxide (H202). It is created and destroyed in the Earth’s atmosphere by delicate balance between the rate of formation and the rate of destruction, both of which vary with increasing altitude above the Earth’s surface. The Ozone layer extends from a height of 20 kilometers to 60 kilometers above the Earth’s surface. Because the air is very thin at these altitudes, if all of the ozone in the Earth’s atmosphere were compressed into a single layer at the Earth’s surface, it would only be 3 millimeters thick. Ozone is important because it is the only atmospheric gas that absorbs light in the B region of the ultraviolet spectrum (UVB).
Palpebrum Eyelid. . Palpebra, Palpebrae, Eyelids.
Palpebral fissure The space between the upper and lower eyelids when the eyes are open.
Pantoscopic Angle, Pantoscopic Tilt The angle or pitch of an eyeglass frame towards the cheeks. See also retroscopic tilt.
Papilla Head of the optic nerve.
1The American Heritage® Dictionary of the English Language, Third Edition copyright © 1992 by Houghton Mifflin Company. Electronic version licensed from INSO Corporation; further reproduction and distribution restricted in accordance with the Copyright Law of the United States. All rights reserved.
Page 22 Glossary of Optical Terms Compiled by Davis Vision
Parallax The apparent displacement or change of position of an object when viewed from different places; such as the alternate use of the right and left eye.
Patients Alternative term used to refer to the plan member, or end user.
PD Abbreviation for interpupillary distance.
Peripheral Vision Side vision. That which an eye can see to the side while looking straight ahead.
Phacoemulsification (Fak oe mul sif ih ka shun) A procedure for removal of crystalline lens in cataract surgery.
Photobrown Glass lenses that turn brown when exposed to the sun.
Photochromic (Fo to kro mik) Glass lenses that darken when exposed to the ultraviolet rays of the sun.
Photogrey Glass lenses that turn gray when exposed to the sun.
Photopic (Fo top ik) Day vision.
Photorefractive Keratectomy (PRK) Refractive surgery to eliminate myopia by flattening the central portion of the cornea with a laser.
Pinnacle Lens Trade name of a private label series of ophthalmic lenses available only at Davis Vision point-of-service locations. The lens is an aspheric design in polycarbonate material with anti-reflective coating and improved scratch resistance.
Plano No Rx
Polaroid (Po lar oid) Two lenses laminated that remove glare. Especially useful for boaters and pilots.
Pole Either extremity of the lens axis at the point it intersects the lens surfaces vertex.
Page 23 Glossary of Optical Terms Compiled by Davis Vision Polished Edge A cosmetic service to make the sides of a cut lens look clear rather than a milky white. This service can be used on any “minus” lens and on most “plus” lenses. It is not beneficial to polish the edges of a lens when:
1. Polished edges negate the antireflective coating by letting light in through the sides. 2. A minus lens (with polished sides) will appear thinner than normal, hence reducing the aesthetic appeal (which was the reason to polish the sides in the first place). 3. On thin lenses, the polished sides are not possible or not visible.
Polycarbonate Highest impact resistant lens material available. Its high index properties result in lenses 20-25% thinner than “regular plastic”. Used for safety, children’s eyewear and sports purposes as well as cosmetics.
Power, Cylinder The difference (plus of minus) between the powers measured in the two principal meridians of a lens.
Power, Marked Surface The nominal curve of a semi-finished lens marked in diopters, as expressed by the manufacturer. The difference between marked and actual tool curveof the surface represents the manufacture’s compensation for that base curve. This compensation allows standard tooling to be utilized over a range of prescriptions with little or no further compensation required by the laboratory to produce accurate vertex powers.
Power, Meridian The refractive or surface power of a lens measured in a specified meridian.
Power, Prism A measure of the amount of deviation of a ray of light produced by a prism or by the prismatic component in a lens, expressed in prism diopters.
Power, Refractive The ability of a lens or an optical surface to produce a change in the convergence or divergence of a beam of light, usually expressed in diopters.
Power, Sphere In a spherical lens, the dioptric power of the lens. In a sphero-cylinder lens, the sphere power is located in the cylinder axis meridian.
Power, Nominal See Power, Marked Surface.
Power, Surface The refractive power of a surface of a material of index of refraction (n) is a measure of its ability to refract light, expressed in diopters.
Page 24 Glossary of Optical Terms Compiled by Davis Vision Power, Surface Tool (S) The actual radius of curvature of a tool or the surface it produces. By common usage in the United States, a tool with a radius of curvature of 530mm will produce a surface tool power (S) of one Diopter. When ( r ) is the radius of curvature in millimeters, then S = 0.5301 (0.001r).
Power, Vertex The Inverse of the distance, expressed in meters, from the lens vertex to the corresponding focal point. This is expressed in diopters. In a prescription, the spherical component of power and cylindrical component are always expressed in terms of rear (or back) vertex power. Focimeters are designed to measure vertex power directly.
Presbyopia (Pres be op ia) A reduction in accommodative ability. Occurring normally with age causing the need for a bifocal.
Prevention A future oriented quality management strategy that principally occurs in the design of process. It involves communicating, planning, proofing, and working up front to eliminate opportunities for nonconformance.
Prevention & Detection A term used to contrast two types of quality activities. Prevention refers to those activities designed to prevent nonconformance in products and services. Detection refers to those activities designed to detect nonconformance already in products and services. Another term used to describe this distinctions is “ designing in quality versus inspection in quality. Phil Crosby described the system of quality as prevention rather than appraisal (detection).
Prism A wedge shaped piece of transparent material which deviates or bends light toward it’s base while the image viewed through it is bent toward it’s apex. Prisms are applied to corrective lenses in order to correct muscle imbalance.
Progressive Addition Lens (PAL) A lens that has no line but progresses from distance to intermediate, to near (i.e. Varilux™, Seiko™, Kodak™, Super Noline™, Rodenstock™, etc.). An all-distance lens.
PSPC (Professional Standards and Practices Committee The PSPC sets clinical standards of practice, conformance with existing protocols, and makes modifications when necessary.
Pterygium (Ter rij e um) Growth on outside of eye which may cover cornea, which is sometimes confused with cataracts by the general public.
Ptosis (To sis) Drooping of upper eyelid.
Pupil The dark opening in center of iris.
Page 25 Glossary of Optical Terms Compiled by Davis Vision Pupil Distance (PD) Measurement of the distance between the pupils.
Pupillary Distance, Monocular The measurement from the center of the nose to the pupil. Also called MPD.
Quadrifocal Lens A spectacle lens with different powers in four different segments, typically for occupational use.
Radial Keratotomy Refractive surgery to eliminate myopia by making a series of radial incisions in the corneal periphery. With healing, the cornea flattens.
Radian The unit of angular measurement generated at the center of a circle by an arc which is the length of the radius of the circle. 360° - 21r radians. 1 radian = 57.29577°.
Ray A straight line representing the direction of a ray or bundle of rays of light. An element of geometrical optics.
Readables Varilux reading lenses with an expanded visual range which provides an extra close range at the bottom of the lens. Ideal for single vision reading lenses. Also available in Varilux bifocal.
Reduced Distance The actual distance divided by the index of refraction in which the distance is measured. In air actual and reduced distances are equal, since n = 1.00.
Refraction (Re frak shun) Loosely referred to as an eye examination (brief eye examination). The measuring of the visual acuity and required correction.
Refractive Care The portion of an eye examination dedicated to the determination of the proper prescription for eyeglasses or contact lenses.
Refractive Errors See Ametropia.
Refractive Index See Index of Refraction.
Resolving Power The capability of an optical system to separate the images of two closely situated points in the object space.
Page 26 Glossary of Optical Terms Compiled by Davis Vision Retina (Ret ih nah) Thin transparent membrane in back of the eye. The light receptive portion of the eye.
Retinitis (Ret ih ni tis) Inflammation of retina (uncommon)
RLX Coating Scratch coating.
Rods One of the two principal nerve endings of the retina which are highly sensitive to low variations in illumination but relatively insensitive to color differences.
Safety Glasses The minimum thickness of the lens is 3.0mm (1mm thicker than conventional lenses). Also, special (stronger) frames must be used instead of conventional dress frame.
Scholaric Shells Refer to Contact Lens definition.
Sclera (Ski rah) White of eye.
Scotoma (Sko to mah) A “blind” spot in the retina.
Scratch Guard Coating Coating applied to spectacle lenses to increases the scratch resistance of the lens surface (i.e. Supershield™)
Sctopia (Sko to pe ah) Night vision.
Seg (segment) Refers to the lower portion of a bifocal lens that contains the reading prescription.
Service Representative The Davis Vision associate responsible for the daily interaction with and authorization of services for all members (and their dependents) and all participating providers with Davis Vision.
Ski Type Coating A combination of lens coatings designed to enhance visual function in snow and high altitude conditions, consisting of the following:
1. A yellow-brown coating on the back of the lens to provide increased contrast and visual acuity in a wide variety of weather conditions.
Page 27 Glossary of Optical Terms Compiled by Davis Vision 2. A double gradient mirror coating on the front surface to deflect harmful and reduced glare.
3. An anti-reflection coating on the back surface to reduce reflected images from behind. Together, these coatings are capable of reducing 100% of ultraviolet light, 90% of troublesome blue light, and 80% of infrared radiation.
Single Vision Lens with one correction for distance or near, as opposed to a bifocal, which has two corrections, one for near and one for distance.
Size See Lens size.
Spectacle An ophthalmic device consisting of two ophthalmic lenses and a supporting frame to position and retain the lenses in proper optical alignment with the eyes.
Slab Off Prism Prism created on a lens by grinding one surface in two portions having separate centers of curvature, to compensate for the unequal prismatic effect when looking through the lower portion of unequal power prescription lenses.
Smart Seg A trade name for a near variable lens. The distance and near segments are the reverse of a what they would be for a bifocal, providing a larger reading area and small distance segment.
Snellen Chart (Snel en) Used to determine visual Acuity (eye chart).
Solid Tint A lens dyed or coated with pigment of uniform color and density throughout the entire lens.
Specular Reflection A reflection from a mirror surface.
Spectralite Trade name of a series of aspheric hi-index ophthalmic lenses. The lens material has an index of refraction at 1.54.
Sphere A plus or minus lens without cylinder or axis.
Spherical Aberration Breach of a point image of a point object by rays refracted from the periphery of a surface to a shorter focal distance than paraxial rays.
Stereoscopic Seeing objects in three dimensions.
Page 28 Glossary of Optical Terms Compiled by Davis Vision Strabismus (Strah biz mus) Deviation of one or both eyes (in, out, up, or down).
Stye An infection of the eyelid at the base of an eyelash. A hordeolum.
Subjective Examination An eye test using patients’ responses to help determine the prescription for glasses.
Sunsensor A trade name for a Photochromic glass available in ready-made sunglasses.
Surface, Aspheric A non-spheric surface curvature commonly used to improve optical performance, particularly for high refractive powers. Such curvatures are often derived from the oblique intersection of a plane and a conical surface and are referred to as “1 conoids’1 or 11 conic” sections.
Surface, Plano A flat surface having zero surface power, or an infinite radius of curvature.
Surface, Spheric A curved surface having the same radius of curvature in all meridians.
Surface, Toric A surface in the form of a torus having different powers in two principal meridians. The shape may be visualized as that of section cut from a doughnut or from a football-shaped surface.
Temple, Library The style of temple that has almost no bend over the ear, it was originally designed for ease of removal.
Temple, Riding Bow A style of temple which bends around to hug the ear. It is particularly useful to people whose jobs are very active, or for small children.
Temple, Screws Tiny screws which connect the front and temple half of the hinges.
Temple, Skull A style of temple that has a slight bend which allows the frame to fit easily over the ear, and to hug the head lightly.
Temple, Spatula Another term for skull temple, also called paddle temple.
Temple, Center The thickness of a lens at the major reference point.
Page 29 Glossary of Optical Terms Compiled by Davis Vision
Tints Normal tints that can be added block between 5 and 20% of light. Darker tint is also available blocking up to 88%. The UV coating is always recommended with a sunglass tint. The most common tint colors are grey, green, and brown.
Tonometer The instrument used to determine the level of pressure in the eye.
Tonometry Testing of intraocular pressure (glaucoma test) using a tonometer.
TPA Therapeutic Pharmaceutical Agents Prescription drugs used by optometrists to treat eye diseases and disorders.
TPA Therapeutic Pharmaceutical Authorization The level of certification of optometrists licensed to use therapeutic pharmaceutical agents.
Transparency Through customization of all plan materials, members visiting independent private professional offices and Davis Vision’s generic telephone answering response, it appears as if the client is actually providing the benefit.
Transitions™ Plastic lenses that turn dark when exposed to the ultraviolet rays of the sun.
Transitions 3™ The third generation of Transitions plastic photochromic lens technology. These lenses are designed to get darker outdoors, have improved lens color, and to clear up indoors more rapidly.
Trifocal Lens A multifocal lens with three different powers in three different positions. Usually, the top largest) portion for distance vision, the middle for intermediate distances and the bottom for near vision.
UCL/LCL Upper control limit/lower control limit.
UCR Usual, customary and reasonable. The doctor’s non-discounted fee schedule.
Ultraviolet Radiation Invisible radiation below visible violet from 4000 AU to the beginning of x-rays, at about 150 AU. Responsible for the tanning effect on ski, and harmful to certain ocular tissue such as the crystalline lens. Sub-divided into three regions called A, B, and C.
A band – The longest ultraviolet rays, adjacent to the visible spectrum with 330 – 400 nanometer range. The ultraviolet rays most likely to present oculars hazard.
Page 30 Glossary of Optical Terms Compiled by Davis Vision
B band – Wavelength range of approximately 275 – 330 nanometer.
C band – With the shortest wavelengths of the ultraviolet rays, between 200 – 275 nanometer.
Unilateral Referring to one side of the head, face of body.
Utilization Review The process of reviewing the appropriateness and quality of care provided to patients
UV 400 Coating A coating that blocks the ultraviolet rays.
UV 400 Lens A factory lens that is treated to block ultraviolet rays from penetrating a lens.
Value-Adding Process Those activities that transform an input into a customer usable output.
Vertex The point on a lens or mirror surface intersected by the lens or mirror axis. In ophthalmic lenses originally related by Von Rohr to the back surface.
Vertex, front - The point from which the neutralizing or front focus of a lens is measured.
Vertex distance - The distance from the back vertex of a lens to the apex of the cornea
Vertex power - The dioptric power of a lens measured from the back vertex. Reciprocal of vertex focal length in meters.
Vertical Meridian The 90-degree meridian in cylindrical surfaces.
Visual Acuity Determine if vision is 20/20 or less
Visual Fields Testing for central or peripheral vision. Not covered under complete eye exam.
Vitreous Humor The transparent gel filling the space between crystalline lens and the retina. It is contained in a hyaloid membrane that is attached to the retina in the area of papilla.
Wave A local ripple-like irregularity in a lens surface.
Page 31 Glossary of Optical Terms Compiled by Davis Vision
“With Motion” Objects sighted through a concave (minus) lens move in the same direction as a concave lens when it is moved from side to side. See also “against motion”
XTRActive Transition Extra dark transition.
X-Axis The imaginary line connecting the centers of rotation of the eyes. The line connecting the geometric centers of a pair of spectacle lenses.
Y-Axis An imaginary line perpendicular to the x-axis and fixation axis through the center of rotation. A line perpendicular to the x-axis of the spectacle lens and optical axis.
Z-Axis The fixation axis of the eye, i.e. the line from the point of fixation through the center of rotation. The optical axis of a lens.
Zyl, Zylonite Most often referred to as “zylo,” although zylonite is a specific type of plastic and although there are several other kinds of plastic, almost all plastic frames are usually referred to as “zylo”.
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