How do you measure eyeglasses?

Answer 1

Measuring eyeglases can get a bit complicated so I'll just put down the basics!

The precription in the lenses can be measured with a focimeter (It looks a bit like a microscope). Prescriptions are most often broken down into four parts:

Sphere - Determines whether you are short of long sighted. (Measured in diopteres)

Cylinder - Dermines Astigmatism (Measured in diopteres)

Axis - The degree at which the cylinder in the lens sits to correctr astigmtism. (Measured in degress)

Prism - Not a very common feature of a prescription. It alignes eyes that are not looking parralel to each other. It has a base direction to determine the exact way in which it is cut into or added to a lens. (Measured in diopteres)

Reading Addition - A positive (+) addition to a prescription for enlargement. It is a Sphere only addition to a precription. (Measured in diopteres)

Eye and Bridge Sizes - The eye and bridge sizes are of a frame measured in mm and are usually printed on the frame itself. The eye size is the largest measurement across the lens and the bridge size is the measurement accross the nose.

Arm Length - The arm length is the distance from the temple to end of the arm on the frame. This is measured im mm.

Pantascopic Tilt - The pantascopic tilt is measured in degress and is the angle at which the lens sits relative to the arm of the frame. Usually this should be between 10 and 12 degrees but this is variable.

Vertex distance - Measured in mm the vertex distance is the distance between the back of the lens and the eye. This should usually be between 10 and 12 mm. Again there are variabes here.

Fitting heights - Mainly used for bifocal, tirfocal, varifocal and aspheric lenses, the fitting height is measured in mm and defines the distance between the optical centre of the lens and the botton of the lens.

These are the very basic glasses measurements and all should vary with prescription and by person. Please leave a message on my board if you need further information.

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Answer 2

Eyeglasses are typically measured using three key dimensions: lens width, bridge width, and temple length. The lens width is the horizontal width of each lens, the bridge width is the distance between the lenses over the bridge of the nose, and the temple length is the length of the arms that go over the ears. These measurements are usually found on the inside of one of the temple arms.