Term
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Definition
| The vertical distance between the furthest top and bottom edges of the lens shape or the distance between the horizontal sides of the box. |
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Term
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Definition
| Lenses are secured in place with clips. The lens can be easily removed and replaced with more that one pair of lenses. In Britain, the frame is called an Ilford mounting. |
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Term
| Basic Optical Frame Types and Parts |
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Definition
| Lenses, Frame front, temples |
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Term
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Definition
Based upon the idea of drawing an imaginary box around a lens shape with the box's sides tangent to the outer most edges of the shape. The system uses the sides of the boxes as reference points for the standard system of measurements. |
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Definition
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Term
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Definition
| Constructed with metal saddle bridge, also referred to as a W bridge. Pad Bridge supports the weight of the glasses. Comfort bridge is an clear plastic saddle bridge attached to the metal frame. |
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Term
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Definition
| Saddle Bridges are shaped like a saddle and rest on the nose. Modified of Semisaddle has nose pad shapes and carry some of the weight. Keyhole Bridge is shaped like a keyhole and rests on the side of the nose and not on the crest like the saddle. Some keyhole bridges use nosepads too. Bridges adjustments in certain plastics like nylon carbon fiber and polyamide are not possible. |
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Term
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Definition
| Plastic frames are either: Solid (all one color); Vertically Gradient or Tutone (darker at the top to the bridge and ligher across the bottom); Horizontal Gradient (darker at the temporal portions and lightens toward the central area); Clear Bridge (resembles horizontal Gradient but the bridge is clear). |
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Term
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Definition
| The horizontal line that runs through the vertical center of the frame. |
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Term
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Definition
| Reference points for frames and lenses to facilitate accurate placement of lens optical centers and bifocal seg heights.The highest and lowest points of the frame are drawn. A line drawn halfway between the two horizontal lines and parallel to them becomes a reference point known as the datum line. The width of the lens is called the datum length or eyesize.The point along the datum line halfway between the edges of the lens is the datum center. Mid-datum depth is the vertical center. |
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Term
Distance Between Centers (DBC) |
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Definition
| The horizontal distance between the geometric centers of the lenses. DBC is also know as the Geometric Center Distance (GCD), but more commonly referred to as the frame PD. In theory the DBC can be calculated by adding the "A" Measurement to the DBL as marked on the frame, however in practice the calculation may differ from the actual measurement. |
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Term
Distance Between Lenses (DBL) |
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Definition
| The shortest distance between the nasal edges of each lens or the distance between boxes. DBL is also commonly referred to as bridge size. |
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Term
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Definition
| Twice the distance from the geometric center of the lens furthest edge of the lens shape. The ED can also be defined as the smallest diameter lens that would cutout, if the frame's geometric center matched the lenses optical center. ED is used in combination with decentration distance to select the minimum lens blank size required to fit a given frame. |
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Term
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Definition
| Butt Type -The front of the is straight and the temple butt is flat at a 90 degree angle. Mitre Type - End pieces cause the frame front and temple butt to meet at a 45 degree angle. Turn Back Type - The frame front bends around and meets the temple end to end. |
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Term
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Definition
| Frames without an eyewire going completely around the lens are called mountings. Lenses are inserted into frames, but 'mounted' into mountings. |
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Term
Frame Contstruction - Combination |
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Definition
| Metal chassis and plastic top rims and temples. |
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Term
Frame Contstruction - Nylon Cord |
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Definition
| Also called string mounted or nylon supras. A grooved lens fits into the upper rim of the frame and nylon filament is stretched into the groove. |
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Term
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Definition
| Bridge, Rim (Eyewire),Endpieces, Metal Shield, Hinges, Barrels(odd numbers), Nose pads (optional) which are attached withmetal pieces known as guard arms or pad arms. |
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Term
Frame Materials- Monel Metal |
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Definition
| Whitish color, is pliable for adjustment. Resists corrosion (via electrolytic treatment) and accepts high polish. Made from nickel(63-70%), copper(2nd largest amt.), iron (2.5%) and trace elements(silicon, carbon,and sulfur). |
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Term
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Definition
| Strong and lightweight. Can be finished in many colors and does not corrode. Does not Soldr or well. Must be made with parts that are assembled with screws or rivets. |
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Term
Frame Materials-Carbon Fiber |
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Definition
| Creates thin, strong frames. Not adjustable and is used mainly for frame fronts. Must fit perfectly the first time. The advantage is its light weight and strong and can be made thin. 60% of the weight of cellulose acetate. Originally black and must be coated with paint. Breaks in cold. |
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Term
Frame Materials-Cellulose Acetate |
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Definition
| Otherwise known as plastic. Made from wood or cotton. Coated with UV to lessen fading and surface is sealed to lessen allergies. Made into sheets and stamped (milled). |
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Term
Frame Materials-Cellulose Propionate
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Definition
| Injection molded and fades easily, so it is dyed. 3/4 the weight of acetate. |
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Term
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Definition
| Kevlar is mixed with nylon. Stable of a large temperature range, but difficult to adjust. Will not shrink or stretch. |
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Term
Frame Materials-Nickel Silver |
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Definition
| More than 50% copper(pliability), 25% nickel (whitish sheen), and the rest zinc(strength), but contains no silver. When the nickel content exeeds 12%, the copper color doesn't show. Another name is German Silver. |
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Term
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Definition
| Highly flexible and will retain flexibilty if occasionally soaked overnight. Overtime will become brittle. Used in sportswear and over-the-counter sunglasses. |
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Term
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Definition
| Epoxy resin which is thermo-elastic. It bends when it is heated and will return to its original shape when reheated. 30% lighter than plastic. |
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Term
Frame Materials-Polyamide |
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Definition
| Nylon-based frame. 72% of the weight of cellulose acetate. Can be made translucent. Resistant to chemicals and solvents. Hypoallergenic. |
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Term
Frame Materials-Polycarbonate |
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Definition
| Molded frames primarily used for sports or safety frames. Nonprescription lenses and frames are molded as one unit. Most impact resistant. do not adjust well. |
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Term
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Definition
| Some sports eyewear and sunglass frames may be made from a combination of nylon and rubber. Very flexible and return to their origninal shape,if bent, but not adjustable. |
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Term
Frame Materials-Stainless Steel |
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Definition
| Made from iron and chrome. Higly resistant to corrosion. Flexible and well suited for temples. |
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Term
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Definition
| Extremely lightweight and will not rust. Can be made super thin but is hard to weld or solder and is expensive. |
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Term
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Definition
The intersection of the Datum Line and horizontal centers of each lens shape. |
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Term
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Definition
| Reading correction frames designed at 1/2 the height of regular frames for reading near only. |
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Term
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Definition
| The horizontal distance between the furthest temporal and nasal edges of the lens shape or the distance between the vertical sides of the box. The A measurement is also commonly known as the eyesize. |
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Term
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Definition
| Hold lenses in place at their nasal edge. The lenses are attached at the bridge area and the temples are attached to a metal arm that extends the posterior surface. There is only one point of contact with the lens. |
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Term
Plastic Frame - Other Names |
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Definition
| Occasionally referred to as shell frames. Also called called zyl (from cellulose nitrate). |
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Term
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Definition
| Rimless(aka as 3 piece mountings) - holds lenses in place by some method other than eyewires or nylon cords like cement, screws, clamps, solder plugs. There are usually 2 points of attachment per lens, one nasally and temporally. |
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Term
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Definition
| The straps mount the front and back surfaces and edge of lenses. Straps consist of shoe and ear. |
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Term
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Definition
| The vertical distance between the Datum line and the top of the bifocal or trifocal segment overall. |
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Term
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Definition
| The vertical distance between the bottom edge of the box and the top of the bifocal or trifocal segment. |
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Term
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Definition
Similar rimless exceptfor a metal reiforcing arm which follows an upper posterior surface of the lens and joins the centerpiece of the frame to the endpiece. The centerpiece mounting consists of bridge, pad arms, and pads.
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Term
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Definition
| Temple position for rimless or semirimless frames was classified as 1)having a regular (on-line) position if the temples were onthe same horizontal plane as the supporting mechanism of the bridge; 2)having a Hibo position if the temples were higher than the regular, but not at the top of the frame; 3)Fulvue position is when the temples were placed at the highest possible position on the frame. |
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Term
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Definition
Library - straight and hold frames in place by pressure against the side of the head. AKA straight-back temples.
Convertible - Similar to Library temples, but are designed to be bent down to take on the form of the skull temples, and can be converted back. Riding Bow curves around the ear following the crotch of the ear and the head and meet and extend to the level of the earlobe. Often used in children and safety frames. Comfort Cable shaped the same as riding bow, but are of metal construction coil cable.
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Term
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Definition
| Attach to the frame front and hook over the ears to help hold the spectacles in place. The nearest attachment to the front is known as the butt end or portion.The place on the temple where it bends down to go over the ear is called the bend. the portionof the temple between the but end and the bend is called the shank or shaft. The portion beyond the bend and behind the ear is call the earpiece, dent-down portion or curl. The hinge barrel is called the dowel hole. |
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