Every industry has its own language and terms. These words and phrases can be confusing to anyone who is not part of the daily operations of a specific sector, and the optician business is no exception.
To help you understand the terms, acronyms, and phrases regularly used when working in opticianry. Frecker Optical has created this handy reference guide. Here, you’ll find valuable information allowing you to comprehend and communicate effectively with other eye care professionals as well as your customers.
Optical Terminology List
Bifocal – Corrective eyewear lenses containing regions with two distinct optical powers. Bifocals are commonly prescribed for people with presbyopia who also require a correction for myopia, hypermetropia, and/or astigmatism.
Blue Light – Blue light, or high-energy visible light (HEV), is a type of light emitted by LED bulbs, computer screens, and the sun. Long-term exposure to this type of light can cause eye strain and fatigue. Harmful blue light, up to 455nm with the greatest toxicity between 415-455nm, is only one contributing factor of retinal aging.
Blue Filtering Lenses – Lenses that filter blue light to help remediate eye strain.
Bridge Size – The width between the lenses on an eyeglass or sunglass frame. Manufacturers typically measure this width at the widest point between the two lenses.
Cataracts – A clouding of the lens of the eye that can lead to blindness.
Clip-On – A small pair of sunglass lenses that clip onto your prescription eyeglasses, often with magnets or hooks. Clip-ons are convenient and easy to use.
Color-Coated Lenses – Lenses with a color coating applied on the outside, rather than a tint mixed into the lens material prior to molding.
Cylinder – An indicator of astigmatism on your prescription. If there is no cylinder value on your prescription, you do not have astigmatism.
Diopter – Unit of lens refractive power (used to measure the correction), equal to the reciprocal of the lens focal length in meters.
Eye Size – The horizontal measurement of the lens at the frame’s widest part. This measurement is listed in millimeters.
Frame Measurements – Most prescription frames will include your exact frame measurements engraved on the temples (arm pieces) or behind the nose bridge area. For more information on sizing frames for eyewear, see our Frame Sizing Guide.
Frame Shape – The silhouette or rim shape constitutes a pair of frames shape. Some of the most popular frame shapes include rectangular, round, oval, and aviator.
Glass – Glass lenses are scratch-resistant and easily tinted, but they’re double the weight of plastic lenses, as they are thicker than high-index plastic and other lightweight lenses. Glass lenses boast excellent optical qualities and their refractive index can be as high as 1.90.
High Index Lenses – Eyeglass lenses that offer a higher index of refraction than standard lenses and can accommodate stronger prescription strengths. High index lens types include:
High Index 1.56 – A lens material that is thinner than plastic and comparable to other high index lenses, resulting in less noticeable lenses that fit a wider range of frames. A flattened, aspheric design makes these lenses up to 50% flatter than regular plastic and 35% flatter than spherical high-index lenses to yield a thin fit and clear optics.
High Index 1.67 – Thinner and lighter weight High Index 1.67 lenses use a higher index of refraction than plastic or polycarbonate—strong prescriptions no longer mean thick, chunky lenses that must be glazed into heavy frames.
High Index 1.70 – A top high-index lens material, 1.70 offers patients with higher prescriptions un-compromised visual clarity in one of the thinnest, lightest weight lenses available. The 1.70 refractive index combined with an unparalleled Abbe Value of 36 transforms even plastic lenses into an optically superior lens option.
High Index 1.74 – High Index 1.74 lenses are the thinnest, flattest, and most cosmetically appealing lens ever developed.
Hinge – A small mechanism generally used to attach frame fronts to temples. Hinges come in several types, including spring, conventional, and proprietary designs.
Mirrored Coating – Also called ‘flash coating,’ this surface coating is applied to the outside of a lens to block 10 to 60 percent more light than uncoated lenses. A reflective lens appears darker and boasts added glare protection.
Nose Pad – The pads mounted to eyewear on either side of the nose to help support the frames, distribute the weight of the glasses, and provide a comfortable fit.
Optical Glasses – Eyeglasses with a prescription added to the lenses. Used to improve vision and allow the wearer to see clearly.
O. D. – Prescription shorthand for Oculus Dexter, meaning the right eye.
O. S. – Prescription shorthand for Oculus Sinister, meaning the left eye.
O. U. – Prescription shorthand for Oculus Uterque, meaning both eyes
Photochromic – Known by the popular brand name Transitions® Lenses, these lenses automatically darken in bright light and become clear again indoors. The lenses are activated by ultraviolet light.
Plano – Flat, having no power, zero, 0.00.
Polarized Lenses – Polarized lenses include a filter to reduce the amount of reflected light that enters the eye, which in turn reduces the glare that can bounce back from water, snow, or concrete and asphalt surfaces.
Polycarbonate – Polycarbonate lenses are the most impact-resistant lens material. Originally used for industrial safety glasses, they are lightweight, boast built-in UV protection, and they’re now recommended for children, athletes, and for use in rimless frames.
Prescription Sunglasses – Sunglasses with a prescription added to the lenses.
Prism – A wedge-shaped lens which is thicker on one edge than the other. Prisms can be used to measure an eye misalignment and/or treat a binocular dysfunction. A prism is sometimes added to glasses to help improve eyesight due to an eye misalignment or visual field loss.
Progressive Lenses – Also called ‘no-line bifocals,’ progressive lenses offer multiple regions of optical power with no discernible line between the regions.
Pupillary Distance or Pupil Distance (PD) – The distance (measured in mm) between the center of the pupils of your eyes. A PD measurement should be obtained by an authorized optical professional only—an incorrect PD can cause eyestrain. If your prescription does not include pupil distance, FramesDirect can measure PD from a photo.
Rx – Short for prescription.
Rxable – means the eyeglass or sunglass frame can accommodate prescription lenses.
Scratch-Resistant Coating – A coating that makes lenses less prone to scratching. We provide a scratch-resistant coating with every prescription at no charge.
Sphere – a number that denotes the strength of the lens in diopters; the sphere is part of your prescription.
Temple Length – The length (in millimeters) of the arm of the frame, as measured from the hinge to the tip of the temple. This number may be obtained by first measuring the temple from the hinge to the place where it begins to curve behind the ear, and from the curve to the tip, and then adding those two numbers.
Titanium – A featherweight metal alloy known for its high tensile strength and durability. Titanium is often hypoallergenic and can be used to make Memory Titanium, a material that will 'remember' or return to its original shape after twisting and bending.
Transitions® Lenses – A popular brand of photochromic lenses that gradually darken in response to ultraviolet light. Transitions lenses block 100% of harmful UV rays. A photochromic treatment can be added to nearly every lens type and material, including shatter-resistant lenses, bifocals, trifocals, progressives, and standard and high-index lenses.
Trifocal – Corrective eyewear with distinct optical powers in three regions of the lenses. The top region of the lens typically corrects distance vision, the middle intermediate vision, and the bottom reading vision.
Trivex Lenses – A revolutionary lens material that offers superior optics, impact resistance, and an ultra light weight.
Ultraviolet (UV) Radiation – Radiation (emission of energy) from the sun and certain artificial sources, including tanning beds. There are three types of UV radiation—UVA, UVB, and UVC. Prolonged exposure to solar UV radiation may result in acute or chronic damage to the eyes. Eyewear lenses should offer UV protection.
UV Filter – A coating added to or embedded within the lens to filter out UV radiation. A UV coating comes standard on all polycarbonate and high-index lenses from FramesDirect.com. Not all sunglasses offer UV protection—check to ensure the fashion sunglasses you order come with 100% UV protection.
Visible Light – The part of the light spectrum the eye recognizes as color. Protective eyewear can safeguard your eyes from excessive amounts of visible light, such as blue light.