Optical Glossarya b c d e f g h i j k l m n o p q r s t u v w x y z Add (or add power): If there is a value under the 'add' heading, then you have a bifocal (or Progressive) prescription. Anti-Reflective Coating: This coating can be applied to the outside or inside surface of any lens (clear or sun lens) to minimizing the amount of light reflected by your lenses thus reducing annoying reflections and distracting glare which may cause headaches or interfere with vision clarity. Regular lenses reflect a very small amount of light back into your eye, possibly skewing vision; anti-reflective coating helps to prevent this anomaly. It is best used on the back surface of a sun lens to minimize back glare. Anti-Scratch Coating: This is applied to the outside of the lens to minimize the likelihood of accidental scratching. This does not make the lens scratch proof, but helps tremendously in reducing fine hair line scratches. All polycarbonate lenses come with an anti-scratch coating. ANZI Prescription Frames ANZI Side shields Astigmatism: Astigmatism is one of a group of eye conditions known as refractive errors. Refractive errors cause a disturbance in the way that light rays are focused within the eye. Astigmatism often occurs with nearsightedness and farsightedness, conditions also resulting from refractive errors. Astigmatism is not a disease nor does it mean that you have "bad eyes." It simply means that you have a variation or disturbance in the shape of your cornea. What causes astigmatism? If the corneal surface has a high degree of variation in its curvature, light refraction may be impaired to the degree that corrective lenses are needed to help focus light rays better. At any time, only a small proportion of the rays are focused and the remainder are not, so that the image formed is always blurred. Usually, astigmatism causes blurred vision at all distances. Some people with very high degrees of astigmatism may have cornea problems such as keratoconus. Astigmatism is very common. Some experts believe that almost everyone has a degree of astigmatism, often from birth, which may remain the same throughout life. The exact reason for differences in corneal shape remains unknown, but the tendency to develop astigmatism is inherited. For that reason, some people are more prone to develop astigmatism than others. Aspheric: Not spherical, an optical surface which departed slightly from a fixed radius of a curvature, reducing the bulge of a lens when viewed in profile. Axis: As mentioned above, a special cylindrical lens is needed in order to correct astigmatism. Not only does the strength of the cylindrical lens need to be specified, but the lens itself must be rotated into a specific position in order to provide the proper vision correction. The axis represents the amount of rotation of the cylindrical lens in degrees ranging from 1 to 180. Base: The base is to the prism what the axis is to the cylinder. As you know, a prism is shaped like a triangle. The thicker the triangle at its base, the stronger the power. Much like the axis specifies the direction of rotation of the cylindrical lens for astigmatism, the prism must also be rotated into a specific position. But the rotation of the prism is simply specified as 'base in' or 'base out' (where 'in' means towards the nose) or 'base up' or 'base down'. Only these four positions exist as opposed to the 180 positions that can be specified for a cylindrical lens. However, orientations between these four positions can be specified by using combinations of horizontal and vertical prisms in the same lens. Base-Down (BD) Prism: a wedge-shaped lens which is thicker on one edge than the other. The thicker edge (base) is turned down. Prisms bend light (opposite direction from its thicker end) so the base-down prism turns the light upward thus causing the eye to also move up. This prism is used to measure an eye misalignment and/or treat a binocular dysfunction (eye teaming problem). Prisms are sometimes added to glasses to help improve eyesight due to a misalignment or visual field loss.
Base-Out (BO) Prism: a wedge-shaped lens which is thicker on one edge than the other. The thicker edge (base) is turned outward, closest to the ear. Prisms bend light (opposite direction from its thicker end) so the base-out prism turns the light inward (toward the nose) thus causing the eye to also move inward. This prism is used to measure an eye misalignment and/or treat a binocular dysfunction (eye teaming problem). Prisms are sometimes added to glasses to help improve eyesight due to a misalignment or visual field loss. Base-Up (BU) Prism: a wedge-shaped lens which is thicker on one edge than the other. The thicker edge (base) is turned up. Prisms bend light (opposite direction from its thicker end (base)) so the base-up prism turns the light downward thus causing the eye to also move down. This prism is used to measure an eye misalignment and/or treat a binocular dysfunction (eye teaming problem). Prisms are sometimes added to glasses to help improve eyesight due to a misalignment or visual field loss. Base Curve: The base curve is the front curve of any lens. The higher the base curve (9 base) the more curved the lenses is thus making the frame more curved. Bifocal lenses: are lenses with two viewing zones, one for seeing distant objects and one for seeing near objects. Bifocal lenses have a line separating the two viewing zones. First invented by Benjamin Franklin in 1784. Bridge: The supportive structural member connecting the two eyes of an ophthalmic frame front. Bridge, Adjustable: Plastic or silicone pads attached to a movable metal arm. The pad arm is adjustable to allow for maximum comfort and will accommodate different nose sizes. 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: Also known as DBL. Is the distance between the lenses on any frame. Smaller bridge fits smaller noses. Contact Lens Base Curve: The curve prescribed by the Doctor to facilitate the best fit and most comfort of the lens. This curve is represented by a number between 8.0 and 9.5. Contact Lens Diameter: The distance from one edge of the lens to the other. The diameter is represented by a number between 13.0 and 16.0 Contact Lens Astigmatic or Toric: A contact lens design effective in correcting astigmatism. Contact Lens Colored Opaque: A type of contact lens that can change eye color Contact Lens Colored Enhancer: A type of contact lens that can enhance the color of a light eye Contact Lens Colored Visibility Tint: A type of contact lens that is manufactured with a light color so it can be seen if dropped on a light colored surface. Contact Lens Bifocal: A lens that has two focal powers. It can be used to see distance and close up. CR-39 (plastic): The advantages of plastic is that it is lightweight and easily tinted to just about any color. One of the disadvantages is that those lenses scratch easily. Crizal - Premium anti-reflective coating that is applied in conjunction with a two sided scratch resistant coating. Crizal Alize - Premium anti-reflective coating that is applied with a two sided smudge resistant, dirt resistant and scratch resistant coating. Cylinder: If there is no value under the cylinder heading, then you have a very simple prescription. If there is a value under this heading, then you have astigmatism. The majority of optometrists write the cylinder value with a minus sign in front while the majority of ophthalmologists (physicians who specialize in the eye) write the cylinder value with a plus sign in front. Regardless of which way this is written, your glasses will be made the exact same way -- these are just two different ways to write the same spectacle prescription. Like sphere power, the cylinder power is also measured in diopters. Diopter : A unit of measurement of the optical power of lenses. For example; if a person has a prescription of -4.00, that person has 4 diopters of power in their lens. Diopters generally are measured in quarter steps like -4.00, -4.25, -4.50. Some doctors refine their measurements down to twelfth steps like -4.00, -4.12, -4.62. Diopters are also used to measure prism. Eyesize or Size: Also known as the “A” measure. It is the horizontal measurement of the lens on any frame. Larger eyesize fits bigger heads. This size is usually marked on the temple or the bridge. See Frame Markings also. Frame Markings: – Each frame is marked by the manufacturer with numbers or words to identify the color of the frame, the name of the frame, and the size of each part of frame. The “A” measurement or eye size is the horizontal measurement across the midline of the lens opening: the larger the number, the larger the frame. The DBL is the smallest horizontal measurement across the bridge. The temple measurement is the total distance in mm or inches from the butt end of the temple to the temple tip. The frame color can be designated by name or numeric color code. The markings can be seen on the inside temple of the frame, the inside bridge of the frame, the nose pad of the frame, or the temple cover of the frame. The most common appearance of the markings might be 54/20 col 20 135. This would mean the eye size is 54mm, the bridge is 20mm, the color # is 20, and the temple is 135mm. 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. G-15 : Green-Gray lenses are the most popular general purpose lenses. Uniform absorption of colors throughout the spectrum allows colors to be seen exactly as they are with approximately 85% light absorption. Glass lenses: One major advantage is that it is very scratch resistant. However it is double the weight of conventional plastic. Also it is not as shatter resistant or safe as plastic. Can easily be tinted. Gunmetal: Dark Grey Frame Color High index: Thinner and lighter than regular plastic good for higher prescriptions. Can easily be tinted into sunglasses. Hyperopia: Also known as farsightedness, is usually inherited. Children are often hyperopic which may lessen as an adult. Hyperopia is a refractive error, which results from a disorder rather than from disease. A refractive error means that the shape of your eye does not bend light correctly, resulting in a blurred image. Impact Resistant: Resistant to shattering or splintering. impact resistant plastic is made so that it will not break into small pieces. Polycarbonate is impact resistant making it a very safe lens to wear. Intermediate: That area in a trifocal lens or blank which has been designed to correct vision at ranges intermediate to distant and near objects. Lens, minus: A lens having negative dioptric power. It is thinner at the center than at the edge. Lens, multifocal: A lens designed for two or more viewing ranges, for example, bifocal or trifocal lenses. Lens, plus: A lens that has positive refractive power. It is thicker at the center than at the edge. Lens, single-vision: A lens designed to provide correction for a single viewing distance. Lens, spherical: A lens that has the same refractive power in all meridians. Such a lens may have rotationally symmetrical aspheric (reflective) surfaces. Mirrored Coating: Also called Flash Coating, it is applied to the outside of the lens and can be applied over any base color. New laboratory processes have created coatings that adhere better to the surface of the lens, are less susceptible to scratching, and are available in an expanded palate of colors. Mirror coated lenses absorb anywhere from 10 percent to 60 percent more light than uncoated lenses, depending on the type and degree of coating. The light transmission is further reduced by the base tint of the lens. Due to its reflective property, any mirrored lens will appear darker since it will reflect a certain amount of light trying to reach the eye. A mirrored lens will also add an extra buffer against glare. This makes them ideal for outdoor uses such as skiing. Care and Cleaning: Because most mirror coatings are applied to the surface of the lens, extra care must be taken when cleaning a mirrored lens to prevent scratching and other damage to the surface. Lens cleaning cloths should be used rather than abrasive cotton or paper towels. Dawn dishwashing soap is a good cleaner, but don’t use other household cleaners such as Windex. Myopia: Also known as nearsightedness, is inherited and is often discovered in childhood. Myopia is a refractive error, which results from a disorder rather than from disease. A refractive error means that the shape of your eye does not bend light correctly, resulting in a blurred image. Myopia often progresses throughout the teenage years, when the body is growing rapidly. People with high myopia have a higher risk of detached retina,which can be repaired with surgery, and glaucoma. Nose pad: One of a pair of pads, usually clear, that rest on either side of your nose and help to support your glasses. Ocular: Ocular is anything of or relating to the eye. O. D.: O. D. simply means 'right eye'. It is the short form of the latin term 'oculus dexter'. O. S.: O.D. simply means 'left eye'. It is the short form of the latin term 'oculus sinister' O.U.: O.U. simply means “both eyes”. It is the short form of the latin term “oculus unitas” Palladium: Matte Silver Frame Color Photochromic: Able to change lens color or darkness/density depending upon the degree of exposure to light. Plano: It is the optical term for the number zero (0). It means no power. Polarized Lenses: Light waves traveling freely can vibrate in any direction. When light strikes a horizontal reflecting surface such as water, sand or pavement, it vibrates horizontally creating glare. To the unprotected eye, glare can decrease depth perception., reduce visual acuity and create eye fatigue. These lenses are great by the water or for driving. A good example of how these lenses work. While driving in your car you often see the glare of the dashboard or if you have a white piece of paper on the dashboard for example you see its reflection off the windshield. Having a polarized lens virtually eliminates this reflection and all of this type of glare (horizontal glare). These lenses are laminated and have a polarizing film in side the lens they are available in gray or brown. They are also available in plastic, polycarbonate or glass. Polycarbonate: Polycarbonate lenses or "Poly" are "impact resistant" thinner and lighter in weight than traditional plastic eyeglass lenses, they also offer ultraviolet (UV) protection and scratch resistance. In addition, they are very impact resistant. This extra toughness makes them the lenses of choice for children's glasses, sports eyewear and safety glasses. Presbyopia: Inability of the eye lens to focus incoming light, resulting in blurred vision at a reading distance and eyestrain. Most people develop presbyopia in their 40s. Prism: This is a box on the prescription form that is rarely filled in. Occasionally, when the two eyes are not properly aligned and looking directly at the same thing, prism can be ground into the lenses in order to re-align them. This can occur with strabismus (i.e. - an eye turn) or in situations where the eyes are properly aligned but are under a tremendous amount of strain in order to keep them aligned. The value under the 'prism' heading denotes the strength of the prism. Progressive lenses: (also, progressive addition lenses or PALs) Multifocal lenses whose corrective powers change progressively throughout the lens. A wearer looks through one portion of the lens for distance vision, another for intermediate vision, and a third portion for reading or close work. Each area is blended invisibly into the next, without the lines that traditional bifocals or trifocals have. Pupillary Distance (PD): The distance between the center of your pupils is known as the pupillary distance, this is measured . Before your prescription lenses are cut into the shape of your frame, the pupillary distance needs to be measured. This measurement is then used so that the optical center of each lens can be lined up with your pupils in order to give optimal visual clarity. In general, PD measurements fall in the range of 48mm to 73mm. The most common measurements are between 58mm and 68mm. Pupillary distance, binocular: The measurement between the patient's pupils, expressed in millimeters. There will be one number which is the total for both eyes. Pupillary distance, monocular: The measurement from the center of the nose to the pupil. There will be two numbers, one for each eye. Pupillary Distance-Distance: This is the measurement between the center of your pupils. It is the number that represents the measurment between your eyes needed to view things in the distance. Pupillary Distance – Near: This is the measurement between the center of your pupils. It is the number that represents the measurement between your eyes needed to view things in the distance. Reading Glasses: Reading Glasses have lenses with stronger powers because they incorporate both the distance and near powers to concentrate power for easy reading for the wearer. Ruthenium: Shiny Silver Frame Color Size or Eyesize: Also known as the “A” measure. It is the horizontal measurement of the lens on any frame. Larger eyesize fits bigger heads. This size is usually marked on the temple or the bridge. See Frame Markings also. Sphere: The number under the heading 'sphere' is the main part of your prescription. The number itself denotes the strength of the lens as measured in diopters. A diopter is a unit of measurement that is simply the inverse of the focal distance of the lens as measured in meters. For example, if a lens has a strength of 2 diopters, then parallel light rays that pass through this lens will focus together at a distance of 1/2 meter (50 cm) away from the lens. If you are near-sighted (i.e. - you have trouble seeing far away but can see fine up close), then you can make a rough calculation of the strength of your glasses. Spring Hinge: Type of hinge on eyeglass frames that is more flexible than a regular hinge, making the frame more durable. Temple Length: Is the length of the "arm" of a pair of glasses, running from the ear to the lens area in Millimeters. Titanium: A type of metal alloy that is very strong. Eyeglasses made of titanium are lightweight and durable and often hypo-allergenic. Transitions Lenses (Day and Night): New Transitions Lenses are so smart they go from clear indoors to as dark as a light sunglasses outdoors. Their advanced technology adjusts to changing light, so you see clearly and more comfortably in virtually any light condition. Indoors, Transitions Lenses are as clear as your regular eyeglasses. Outdoors, they quickly darken, getting as dark as sunglasses a Sunglasses "2" if UV is present. They work so well, in a recent clinical study, four out of five eyeglass wearers preferred Transitions to their regular lenses. And Transitions provide 100% UV protection. Ask your eyecare professional about making Transitions Lenses your every day lenses. And find out just how smart a lens can be. Ultraviolet (UV) Radiation: Solar radiation is formed by visible and invisible light waves. Measured in nanometers, it has three wave lengths that reach and affect your eyes: Ultraviolet, Visible Lights, and Infrared Radiation. UV Filter (coating): This coating is a filter for the harmful UV radiation. The coating is either put on the lens or is imbedded into the lens to protect your eyes for the harmful effect of the sun’s UV radiation. Varilux Lenses: The leader in progressive line-free bifocals for over 20 years. Varilux continues to lead this category. Wrap or Wrap around: Wrap glasses are those that curve around the curve of a person's face fitting close to the head. |