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  Interpreting Your Spectacle Prescription Previous Page Next Page 
Interpreting Your Spectacle Prescription
Isyte.com feel it is important that you understand your particular eye problem and part of that includes interpreting your own spectacle prescription. The form you see below is a typical layout of a spectacle prescription. No longer will this be a mysterious set of numbers and symbols. If you would like to click on the headings in the prescription form above we will explain their meanings


SphereCylAxisPrismBaseAdd
R
L

R - Denotes Right eye. This is sometimes written as O.D, which is the abbreviated Latin equivalent.
L - Denotes Left eye. This is sometimes written as O.S, which is the abbreviated Latin equivalent.

Sphere
This figure represents the power in Dioptres of the spherical lens required to correct your sight. People who are Myopic or short sighted need negative powered lenses such as -1.00 or -3.00. The lenses change in 0.25 dioptre steps, myopic people can focus well for close work but cannot see distance clearly.

People who are Hypermetropicor long sighted need positive powered lenses such as +2.00 or +5.00. These lenses also change in 0.25 dioptre steps.Hypermetropic people generally have more difficulty seeing close work clearly however depending on the degree of Hypermetrodia and age of the person the prescription may be required for distance viewing as well.

People who are Presbyopicor who just need glasses for reading also require positive powered lenses generally these people are over 40 years of age. These lenses enable the person to read but will blur the distance vision.

Cyl
A Cylindrical lens or Cyl is the type of lens used to correct Astigmatism.

What is Astigmatism?
Astigmatism is caused by the eyes optical surfaces (such as cornea or lens of the eye) not being spherical, and hence being elliptical. This causes de-focusing of the eye for distance and near. To correct this problem a lens is required that has the power in only one direction or axis. This is a cylindrical lens.

Axis
The axis relates the cylindrical lens, and denotes a reference point that indicates the direction of the power of the cylindrical lens. This is measured in degree steps from 1 degree to 180 degrees.

Prism
These lenses are used less frequently than sphere, Cyl, and ADD. Their function is to move an image up, down, left or right. This type of lens is used to correct double vision, either intermittent or constant (which is called a Tropia), or a tendency of the eyes to not work perfectly together, and one eye wanting to drift slightly, (this is called a Phoria).

Prism lenses are measured in units called Prism Dioptres.

Base
The Base relates to the direction of the Prism and denotes a reference point to tell us in which direction image has been moved.

This direction will be recorded as either:
  • Up

  • Down

  • In

  • Out


  • For Example:
    RL
    (prism Dioptre) BASE IN(prism Dioptre) BASE IN

    Which can also be recorded as 2^ Prism Dioptres Base in overall.
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