Understanding Contact Lenses Prescription

 

How to Read your Prescription

You don't need your physical prescription with you in order to purchase contact lenses from Eye Contacts, but you do need to have a good understanding of what it is. You can find your prescription on the piece of paper given to you by your optometrist and on the end side of your contact lens box or on the blister packs that contain your contact lenses.

A contact lens prescription is made up with the following specifications:                    base curve, diameter, sphere(or power). If you have an astigmatism two additional specifications will be needed; cylinder and axis. To correct presbyopia; an addition and dominance will be needed it can be written simply as; high or low, or a number followed by D for dominant or N for near.

The prescription for your left and right eye will be listed separately as they can vary.

When a prescription is preceded by a

+ This indicates Hypermetropic/far sighted vision , and when preceded by a

- This indicates Myopic/near sighted vision

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 (Sph)

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 Hypermetropic or 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 Hypermetropia and age of the person the prescription may be required for distance viewing as well.

People who are Presbyopic or 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.

Cylinder (CYL) Toric Prescriptions

A Cylindrical lens or Cyl is the type of lens used to correct 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 (Axis ) Toric Prescriptions

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