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Optical Terms and Definitions


a number given to describe the amount of chromatic aberration of a lens material. Describes the clarity outside of the optical center. Higher ABBE, less aberrations.

Add power
the power/magnification required for near vision.

Anti-Glare, Anti-Reflective, AR
is a microscopically thin multilayer coating that eliminates reflections from the front and back surface of eyeglass lenses.

when the cornea (the clear front cover of the eye) is irregularly shaped. Describes the lack of ?roundness? of the cornea.

the angle of your astigmatism correction.

A lens deign that offers two different power corrections with a visible segment. Generally has distance correction on the top and a segment for reading.

Digital Lens
Refers to a lens fabricated by computer controlled surfacing equipment. Offers better acuity and better overall vision through the lens. Can result in a lens that is thinner and lighter than non-digital lenses. In progressive lenses, can provide fields of view 20% wider than non-digital lenses.

Drilled Rimless Frame
Any frame that requires drilling to hold the lens in place.

Fitting Height/ Seg Height/ OC Height
The vertical measurement from the bottom of the lens to the center of the pupil.

Near sightedness. Trouble with far vision.

Latin terms for righteye/left eye respectively. OD - oculus dextus. OS - Occulus Sinister.

An eye care physician specialized in the treatment of eye disease, eye conditions and eyesight correction.

An eye care professional trained to measure and fit eyeglasses to the wearers needs.

An eye care professional trained to perform reflective eye exams, fit contact lenses and assess overall eye health.

Variable tint lens that can darken and lighted depending the amount of UV exposure

PhotoFusion A Zeiss brand of photochromic feature.

Polarized Lens
A polarized is a Sunglass lens with a layer in the material intended to reduce glare and block reflections. Polarized lenses are not available in clear options.

Polycarbonate A strong, lightweight, impact resistant material. A type of ophthalmic plastic.

Eyesight condition caused by aging of the crystalline lens. Causes loss of near vision use. Prescription will have an ADD power.

Progressive Lenses
A lens design that offers correction of multiple fields of view. Progresses from far vision correction at the top, to near vision correction at the bottom of the lens. Corrects presbyopia.

The central opening of the iris. Dark center of the eye.

Pupil Distance
The measurement between the pupils of you eyes. Can be measured pupil to pupil or center of nose to each pupil.

Refractive Index
A property of the material that describes how it bends light. Higher index, better refraction. High index lenses refract better than low index material and therefore require less material to refract the same power; results in a thinner lens.

Semi-Rimless Frame
Two types: 1. A frame that does not have an eye wire around the full perimeter of the lens. Has an exposed edge on any side of the frame. 2. Requires a groove in the lens to hold in place. Often look like a fully rimmed frame but requires a groove.

Single Vision Lenses
A lens design that offers the same power correction throughout the entire lens.

Tinted Lens
A lens that starts clear and is dipped into a dye to create a fashion or sunglass lens.

Transitions An Essilor brand of photochromic features.

Trifocal Lenses
A lens deign that offers three different power corrections with a visible segment.