Understanding Contact Lens Prescription Made Easy

Understanding Contact Lens Prescription is the next important task after having understood the importance of a prescription. While the prescription slip may seem to be Greek and Latin to an average eyes, this article should help you understand what each component of the prescription means. It is just a matter of you getting used to the terminologies, measurements and standards. As with most Contact Lens Prescription slips, here are the words that you will be bumping into:

OS and OD: They are written in columns and represent your right and left eye. OS is the abbreviated form of Oculus Sinister which is a Latin phrase for the left eye. Similarly, OD means Oculus Dexter which means right eye in Latin.

Sphere or Power: The lens' refractive power is called as the sphere and is always measured in diopters. The number that is written is the correction amount that your eye needs. A farsighted person who is referred to as hyperoptic will have a plus sign while a nearsighted person, referred to as myopic, will have a negative sign.

If there is no correction required, that is represented by a zero.

Base Curve: This is the curve of the lens, and is measured in mm (millimeters).

Diameter: This again, measured in millimeters, is the diameter of the lens.

Brand: While this may surprise a few, it is necessary for Opthalmogists to name the brand that the eye will need. It is a law in the United States, and retailers should and must only sell the indicated brand.

The following are some terminologies which are sparingly used depending on the situation:

Axis and Cylinder: Only if you suffer from astigmatism, you will find the terms axis and cylinder in your prescription. Cylinder is always measured in diopters and stands for the magnitude of astigmatism. It is similar to the refractive power, a - (negative) sign means one is farsighted (myopic) while a + (plus) sign means that the person is nearsighted (hyperoptic).

The axis is calculated in degrees and stands for the direction of the tube (cylinder) that is required.

Add Power: If are prescribed for a bifocal contact lens, that's when you will see this on contacts. It stands for the power needed, again measured in diopters, for viewing close subjects/items or for reading.

Color:It is only when you need special-effects Contact Lenses that you will see the mention of color in the prescription.

With these explanations, you are now in a much better stage in understanding contact lens prescription. If in doubt, always ask your doctor.