A contact lens prescription has a series of fields that are not included on your eyeglass prescription. These fields signify important aspects, like the curvature and depth of the contact, to ensure that your contact lenses fit and function properly. Eye doctors use standard terms, abbreviations and measurements to write contact lens prescriptions. It may look like a secret code, but it's really quite simple to decipher. The prescription may also have an expiration date, brand name, and other fields, but most of these are optional by the doctor. By using these universal terms to describe ocular imperfections, prescriptions can be interpreted by eye doctors around the world.
Understanding Contact Lens Prescription & Terminology Used in this Test
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| Contact Lens Prescription |
Eye: - Which eyes the prescription line item is for.
- OD - Right Eye
- OS - Left Eye
- OU - Both Eyes
- R - indicates the right eye. Sometimes written as O.D.
- L - indicates the left eye. Sometimes written as O.S.
Brand: - The brand/type of contact lens that your doctor has fitted you for. In the United States, lens prescriptions always indicate a specific brand. The law states that US retailers must sell you that brand and no other. In the case of a “private label”, contact lenses that are sold only by eye care professionals, substitutions of an equivalent natural brand or private label brand may be permissible.
Power sign Either + (plus) or - (minus). Power, the diopter measurement needed to correct your vision.
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| Contact Lens Prescription Terminology |
Sphere (Sph): - Sphere (this can also be referred to as Power or PWR), is a number between +20.00 and -20.00. Plano means the lens has no optical power and does not correct vision. The number might be very small, like 0.25, or a large number, like 6.00. The higher the number, the stronger the prescription lenses required. This can influence your choice of frames. The higher the prescription, the greater the curve of the lens needed.
Cylinder (CYL): - It is a number between -0.50 and -4.00 and is only found in Toric Prescriptions to correct astigmatism. Measured in diopters, the cylinder shows the extent of your astigmatism. A negative sign means Myopia (nearsightedness) astigmatism and a plus sign means Hyperopia (farsightedness) astigmatism.
Axis (Axis): - is a number between 1 and 180 and is only found in Toric Prescriptions to correct astigmatism. The axis is measured in degrees and indicates the orientation of the cylinder in the lens and is used in order to compensate for the cornea’s oval, rather than round, shape. The number is not related to how well you can see but it helps the lab know what angle to position your lenses in the frame.
Often the Sphere , Cylinder and Axis of prescriptions will be written all together in the following form: SPH / CYL x AXIS and will look something like -1.00/-0.75 x 90.
ADD: - is a number between +0.50 and +4.00 only found in Bifocal or Multifocal lens prescriptions. If you are over 45, there may be a number where it says ‘ADD’. This is your reading addition and relates to the amount of additional correction needed to focus at close distances. If a measurement is shown in this section, it means you have different prescriptions for distance and reading. Bifocal or varifocal lenses may be needed.
Base Curve (BC): - Curve (usually a number between 8 and 10), Number between 7.0 and 9.5 which determines the looseness or tightness of a contact lens. It’s the back curvature of your contact lens and is measured in millimeters. For best fit, comfort and eye health it’s prescribed to match or complement the curvature of you cornea. The lower the number, the steeper your cornea.
Diameter (DIA): - Diameter (usually a number between 13 and 15), Number between 13.0 and 15.0 and is the diameter of the contact lens. It’s the distance, measured in millimeters, from one edge of your contact lens to the other edge. It’s important because it determines where on your eye the edges of the lens will rest. If the diameter is wrong, it can cause irritation and/or abrasions.
Lens Tinting: - This is the tint or colour of the contact lens. Some lenses are clear and most have a very light tint called a visitant which allows you to see the contact lens slightly more easily when handling it. Tinted contact lenses have a variety of colors to choose from to change your natural eye colour.
Conclusion
As we know a contact lens is a thin lens, made of flexible or rigid plastic, that is placed directly on to the eye to correct vision, used as an alternative to spectacles, or, if colored, to change one's eye color cosmetically. It is a corrective, cosmetic, or therapeutic lens usually placed on the cornea of the eye.Contact lenses are more versatile than glasses making it easier to participate in a number of outdoor activities and sports such as jogging, golf, tennis, skiing or skating. By wearing contact lenses you now have the option of choosing from a variety of non-prescription sunglasses for sport and fashion.
Your doctor will recommend the best contact lenses for your eyes based on a complete eye examination and a review of your visual needs both at work and play. Success with contact lenses depends upon a certain amount of motivation and a commitment on your part. You must learn to take proper care of both the lenses and your eyes.
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