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Glossary of Terms

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ABS Absorption ( tint )
The degree of visible light a tinted lens will absorb ( block ) from the users eyes.
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Add

This is the amount of extra spherical power needed to convert your distance prescription into a reading or intermediate prescription.

The name of the focal distance preceeds the add, i.e Near Add +1.75.

Or follows the add value, i.e Add +1.75 Near
Axis
The direction in degrees that a Cylinder is rotated to to correct Astigmatism
Base
Base - Is the direction of Prism - IN -OUT - UP - DOWN - It can also be written as radians 0 - 360
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BVD
Back Vertex Distance Is The Measurement In Millimeters From Your Eye To The Rear Surface Of The Framed Lens
Cylinder " CYL "
The curve of the lens is set in one direction only
DBL
Distance between lenses, the shortest distance between a pair of lenses within a spectacle frame.
DS "Dioptre Sphere"
This lens is Spherical only. "No Cylinder"
Distance RX
The RX provided to allow the user to focus correctly at long distances.
Focal Range
The distance from your eyes at which you can focus comfortably, Distance, Reading, Intermediate
Full Rim
A spectacle frame that has a rim all around each lens.
Intermediate RX
The RX provided to allow the user to focus correctly for Computers ( at arms length or a little greater ).
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Middle RX
The RX provided to allow the user to focus correctly for Computers ( at arms length or a little greater ).
Multifocal
Any lens tat is designed to allow the user to focus at more than one focal distance eg. bifocal, varifocal etc.
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Near RX
The RX provided to allow the user to focus correctly for reading ( a little under arms length ).
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PD or Pd
Pupillary distance, the exact distance between the pupils in millimeters.
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Prism
Prism - Is used to correct convergence problems - It is quite rare and not often prescribed
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Pupillary Distance
PD , the exact distance between the pupils in millimeters.
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Pupil Height
The measurement in mm between the lower edge of the lens directly below the pupil and the pupil middle
PX
 ( latin )
Patient.
Reading RX
The RX provided to allow the user to focus correctly for reading ( a little under arms length ).
Reglaze
The fitting of new lenses into a patients own frame.
Rimless
A spectacle frame with no rim above or below the lens.
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RX
 ( latin )
Prescription.
Semi Rimless
A spectacle frame where a rim exists only above or only below the lens.
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Scratch Resistant
A very durable coating is applied to both surfaces of the lens to increase resistance to scratching, this will not make the lenses scratch proof, there does not exist a completely scratch proof lens.
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Sidelength from front to tip
 side length from front to end of tip
A manufacturers marked side length will be from screw, but as the front trims vary in length this is of little help to an online client, so we show this measurement to demonstrate the useable sidelength.
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Sidelength from front to bend side length from front to bend ( over ear )
A manufacturers marked side length will be from screw, but as the front trims vary in length this is of little help to an online client, so we show this measurement to demonstrate the overall side length to bend.
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Sph
Sphere - The part of your prescription that magnifies or reduces the image size
TRS
 ( tint )
The degree of visible light a tinted lens transmits ( lets through ) to the users eyes.
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VA 6/6 6/9
Visual Arc, your Optician keeps a record of this value to check for changes, during future eye tests
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VDU RX
The RX provided to allow the user to focus correctly for Computers ( at arms length or a little greater ).
Voucher
An official form with a monetary value redeemable against prescription glasses. May be supplied by your NHS Optician or in the case of corporate vouchers by your employer.

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