Explore the definitions of sunglasses-relevant words and phrases in our glossary of common eyeglass terminology.
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Abbe Value: the index used to measure the chromatic aberration in lenses and the color fringes above and below, or to the left and right of a high contrast object.
Absorption Factor: the amount of light absorbable by a tinted lens.
Acetate: a type of plastic often used and associated with sunglass frames and lenses.
Acrylic Plastic Lenses: this type of lens typically weighs less and is the least expensive. They are usually soft and scratch easily.
Aluminum: a type of metal used to make sunglasses. It is currently used less than in the past.
American National Standards Institute (ANSI): the American National Standards Institute develops voluntary standards for sunglasses among other products, and is mentioned in many sunglass brands’advertisements.
ANSI Z80.3: as applied to special-purpose sunglasses, the Z80.3 standard effectively assures that the lenses screen 99 to 100 percent of harmful UV rays and permit acceptable color recognition.
ANSI Z.87.1: a sunglasses classification which assures a great amount of protection against impact.
Anti-reflective (AR) Coating: a thin layer of coating applied to a lens in order to reduce the amount of reflected light and glare that reaches the eye.
Authentic Rx Lens: a custom order that comes directly from the frame manufacturer, providing the consumer with all the features of that manufacturer’s specialty lens, along with the consumer’s prescription.
Aviator Glasses: eyewear resembling those worn by aviators, or people who fly aircraft; they typically have a metal frame and large, tinted lenses.
Axis: verifies the placement in degrees of the astigmatic lens.
Backside Coating: coating that functions to protect the sunglasses lenses from scratching.
Ballistic: shatter-resistant, rugged sunglasses that typically exceed ANSI Z87.1 safety and military MIL-STD-662 standards.
Barberini: a type of lens formed by the smelting of inorganic oxides that does not break, shatter, crack or wrap.
Base curve: the degree of wrap in sunglasses lenses; typically ranges between 6 and 8.
Base tint: a dye embedded in the lens that creates the color seen when one looks at the back side of a pair of sunglasses.
Bifocal: a type of lens containing two regions with two distinct optical powers.
Blue Blocker: a type of lens that guards blue light.
Blue Light: a part of sunlight which is blocked by yellow or amber lenses, making objects appear more distant to the eye.
Bridge: the area that arches up between the lenses over the nose and supports the majority of the weight of the glasses. There are several different types of bridges:
A keyhole bridge is shaped like an old-fashioned keyhole and rests on the sides of the upper part of the nose. This style is best suited for those with small or flat-topped noses.
A saddle bridge is shaped like a saddle and spreads the weight of the frame across the sides and the top of the nose. This style works well for heavy glasses or for those with sensitive noses.
An adjustable bridge includes nose pads that can be bended and moved for fit and comfort.
A double bridge has a reinforcing bar over the top of the bridge.
Bridge Size: the distance in millimeters between the inner sides of the lens.
Brown and copper: colors that sharpen contrast while authorizing accurate color perception.
Cable Temple: a style of sunglasses that wraps around the ear in order to keep them well-fastened and secure.
Carbon fiber: a distinct material that is very strong and hard to adjust; used to make sunglasses.
Case: a hard protective box fitting to standard sunglasses size, intended to keep sunglasses and lens safe and secure.
Cellulose Acetate Zyl: a type of plastic that is of medium-weight, flexible, and strong. Zyl frame temples have metal reinforcements that will make them stronger.
Clip-on: a type of sunglasses that “clip”, or attach, onto one’s reading or eyeglasses.
CR-39: an optical quality plastic that is made of hard resin and considered to be the top plastic for lenses.
Coatings: surface lens treatments that achieve special cosmetic purposes. Types are as follows:
Anti-reflective:
- can reduce distracting reflections that are particularly common with curved lenses.
Hydrophobic: sheds water and sweat to reduce spotting on lens surfaces.
Mirrored: a cosmetic coating, which has the appearance of a mirror and can reduce glare and bright light.
Scratch-resistant: also known as “hard coating”; helps polycarbonate, CR-39, and other plastic lenses resist scratching.
Color-Coated Lenses: a type of lens with a color coating applied to its outside.
Contrast: the difference in brightness between the light and dark parts of an image.
Cornea: the transparent front part of the eye that covers the iris, pupil, and anterior chamber, and controls most of the eye’s optical power.
Cylinder Glasses: a lens with two different curves that corrects a refractive error where the image of an object hass two focal points at different distances.
Diopter: the unit of lens’s refractive power, equal to the reciprocal of the lens’s focus length in meters.
Drive Wear: a type of transitional lens specifically designed for driving that transitions behind the wind shield of a car.
Endpiece: parts of the frame fronts that extends outward from the lenses and connect to the temples.
Eye Size: the horizontal measurement of the lens from one end to the other, in millimeters.
Flash Coating: a highly reflective coating that greatly reduces the amount of light that reaches your eyes.
Frame Colour: the color of the frame.
Frame Front: the front part of the eyeglass frame that holds the lenses in place and bridges the top of the nose.
Frame Eyewire: lenses are inserted into this part of the frame front.
Gradient Coating: a permanently shaded, double-gradient lens that is dark at the top and bottom and lighter in the middle.
Graphite: a material used for sunglasses that combines carbon and fiberglass materials, and is extremely lightweight and strong.
Gray and green: colors that are neutral and soothing to the eye.
Glare: a condition caused by a direct light source (the sun) or is reflected from a surface (roadway, water) that is irritating to the eye.
Glass: optical-quality glass is the material of choice for excellent clarity and resistance to scratching.
Grilamid: a rugged, resilient material used for making frames that is specifically formulated for flex, impact strength and dimensional stability.
Ground and polished: a process applied to some non-prescription glasses when they are manufactured to improve the quality of the lenses.
Hard Coating: a hard scratch-resistant coating used on CR39 lenses, which provides extra lens protection.
High Index: a type of lens with an index of refraction that is very dense, allowing the lens to be thinner.
High Index 1.56: lenses that are 25 percent thinner than plastic and comparable to other high index lenses, allowing for thinner lenses and a wider variety of frames to choose from.
High index 1.67: a thin and light-weight lens, designed with a built in UV protection.
High Index 1.70: a type of lens with built-in UV protection and automatically anti-reflective coating.
High Index 1.74: the thinnest, flattest most technologically developed lens ever made; said to be the most aesthetically pleasing lenses.
Hi Index Glass Lenses: available in a wide range; 1.6 high index lenses can be finished to a 1.5 mm centre in minus prescriptions and still meet United States FDA impact resistance standards.
Hinge: the part of the frame that connects the frame front to the temples and allows the temples to fold in. Hinge types are as follows:
Barrel:
- the most commonly used type of hinge. Interlocking pieces can be found on the inside face of the frame are kept together with a small screw.
Interlocking:
- very similar to the barrel hinge, but the hinge is actually part of the frame itself. Usually found in plastic frames, the joint is molded into the frame pieces and there are no separate hinge pieces holding the frame together.
Spring: spring hinges use a spring tension to press the temples of the frame closer to the sides of your head.
Break-away: these hinges are made from interlocking plastic parts that “break away” or separate when a significant impact from the outside occurs. These hinges, found mostly on sport sunglasses, will prevent damage.
Hydrophilic: used in frame temples and nose pads, providing a stronger bond with high moisture.
Hydrated Nylon: said to be the sunglass industry’s most durable material; it is virtually unbreakable, and has excellent memory.
Impact Resistant: a polycarbonate used in lenses and frames that is safer than traditional materials because it is not brittle and will hold up better under direct impact.
Infrared (IR) Radiation: long wavelength rays, sometimes called “heat waves” that cause the skin to feel hot and may contribute to the discomfort caused by exposure to bright light.
Interchangeable Lens: when different lens colors and types that can be purchased in excess of an existing pair of lenses.
Lens: the clear, plastic or prescription part of sunglasses that one looks through, and that is resistant to light.
Lens Size: the size of a lens in millimeters when measured horizontally.
Megol: a soft and pliable rubber that provides a comfortable and slip-resistant fit.
Melanin polarized lenses: a highly protective lens treatment that works against UV radiation, blue light and glare.
Metal Frames: frames made from base metals, or copper or nickel alloys, that are later plated with fine metals, such as gold, to give them a rich finish.
Monel: durable nylon material that is virtually unbreakable, and includes a type of elasticity, or memory, that returns the material to its original shape.
Nylon: a lightweight, flexible and durable synthetic material, which is derived from coal, water, and air.
Nose Pads: plastic pieces which may be attached directly to the frame or pad arms. These help keep the frame in its proper position on the wearer’s face, while providing comfort and a snug fit.
Ocular: anything related to the eye can be described as “ocular”.
O. D. & O. S.: O.D. pertains to the right eye, and O.S. pertains to the left eye.
Optical clarity (acuity): the ability of a lens to deliver a sharp image to the eye.
Optically Correct Lens: when looking through a non-optically correct lens, one’s eye will continually refocus due to distortion. Optically Correct Lenses defeat negative outcomes of a non-optically correct lens.
Optyl: a hypoallergenic plastic material made especially for eyeglass frames. which features a type of elasticity, or memory, that returns the material to its original shape.
Pad Arms: attachments that hold nose pads in place and allow adjustments to help conform to a wearer’s bridge.
Pentax: a type of lens that is extremely thin and light. It has used the highest index of refraction, at 1.67.
Peripheral Vision: the edges of one’s visual field.
Photochromic Coating: a type of coating that will automatically darken and lighten when the light changes.
Polarized Lenses: a filter in between the front and back surface of the lens, which filters out horizontally reflected glare.
Polycarbonate: an extremely strong plastic that weighs little and is impact-resistant, making it an ideal selection for use in rugged sunglass frames and lenses.
Prism: a wedge-shaped lens that is thicker on one edge; it is used to measure an eye misalignment and to treat a binocular dysfunction.
Progressive lenses: no-line bifocals.
Protective Glasses: eyewear made with impact-resistant lenses, usually polycarbonate, that protects the eyes.
Pupillary Distance: the distance in millimeters between the centers of the pupils of the eyes when looking at something far away.
Rim Type: a description of lens placement. “Full rim” is most typical, which occurs when the lens is completely encased in the rim of the frame. “Semi rim” appears occasionally, which describes a condition in which the lens is encased in the top of the frame; also called “rimless”.
Rock Hard CR 39/AR: a lens type that is five times more scratch resistant than regular CR 39 lenses, with 3 layers of antireflection on the backside to eliminate sunlight reflection from behind.
Rose: a color that sharpens details and allows for quality depth-perception.
Round-Seg Bifocal: features a round reading section for the bifocal lens that is placed on the back of the lens rather than the front, allowing the lens to be closer to the eye.
Safety Glasses: a type of frame that is more durable than fashion frames; the lenses must be able to pass a “drop ball” test.
Screws: tiny metal fasteners found at eyeglass hinges which connect the temples to the frame front; and on the bridge, which hold the nose pads in place.
Serilium: a combination of polycarbonate plastic and nylon that has the same durability as nylon, but is sturdier.
Side Pieces: eyeglass pieces which curl behind the ear, resembling a hockey stick; attached to the end of “straight sides”, which grip above the ears.
Silicon: a type of flexible and comfortable plastic that is commonly used in nose pads.
Sphere: the sphere number of your lens indicates the strength of the lens, in diopters.
Spring Hinge: a type of hinge on eyeglass frames that is more flexible than a regular hinge, allowing for better fit and durability.
Stainless Steel: a type of steel comely utilized in eyeglasses; stainless steel frames can be made very thin, while still maintaining their strength and flexibility.
Sweatbar: a metal bar that rests over the bridge to provide extra support; not necessarily featured in all eyeglass models, but is common in aviator styles.
Temples: “arm” pieces of the frame that extend over and/or behind the ears to help hold the frame in place. There are several types of temples:
Skull temples
- are most popular for plastic frames. They appear bent down slightly over the ear and follow the contour of the skull.
Comfort-cable temples hook behind the ear with a flexible metal cable. These are suitable for children’s styles and sport-safety glasses.
Riding bow temples are similar to comfort-cables, except they are rigid and made of plastic.
Spring-hinged temples include hidden springs in the hinges that help keep the frame from slipping. These are sometimes more expensive, but typically more resistant to breakage.
Library (or paddle) temples are straight, so they can be slipped on and off easily. This type is often used in reading glasses.
Temple length: the length in millimeters of the arm of the frame that runs from the hinge to the end that wraps behind one’s ear.
Temple tips: plastic coatings that often cover the ends of the temples behind and/or over the ears to provide wearer comfort. Their use is common in regard to metal glasses.
Titanium: a type of metal alloy that is very strong and used to make sunglasses lightweight and durable.
Top bar: a reinforcing bar that crosses the top of the glasses, between the two lenses, on some metal frames; popular in aviator style glasses.
Transitions Lenses: a kind of Photochromic lenses, which transition from clear to dark in the presence of ultraviolet light and blocks 100 percent of harmful UV rays.
Transmission Factor: the ratio of light that is passed through the lens.
Trifocals: a type of corrective eyewear lenses, which contains regions with three distinct optical powers.
Trivex lenses: a very fine type of lens, which allows one to be prescribed a single, thin lens with the qualities of many different lens types.
Ultraviolet (UV) Rays: the invisible part of the light spectrum, at which rays have wavelengths shorter than the violet end of the visible spectrum and longer than X-rays; they are very dangerous to the eyes.
UV Filter: a lens coating that filters out UV radiation.
Visible Light: that part of the sun’s energy that one can see, and is made up of a spectrum of colors: red, orange, yellow, green, blue, and violet.
Wrap-around: a type of eyeglass frame that curves around the head, from the front to the side.
Yellow: a color that enhances depth perception in low-light conditions, while permitting excellent detail.
Zyl: a material used in a variety of plastic materials used in making eyeglass frames, the most common of which is Cellulose acetate.