Whether you're brand new to wearing contacts or have been wearing them for years, the language and abbreviations on your contact lens prescription can be a bit of a mystery.
Terms and Abbreviations
Standard Lens Terms
These terms and abbreviations apply to all contacts lens users, and describe the basic factors that play into a prescription.
- Power (PWR) - sometimes referred to as sphere (SPH), this is the strength of your prescription. As the power goes down in negatives, the strength of the prescription increases. For instance, -2.50 is a stronger power than -1
- Plano (PL) - this indicates that the OD or OS does not need any correction
- Base curve (BC) - typically ranging from 8 to 10 millimeters, this term describes the curvature of the lens, and how it conforms to the shape of your eye. The lower the number, the steeper the curvature of the lens
- Diameter (DIA) - just like in geometry, the measurement of a straight line through the middle of the contact lens. Similar to the base curve, diameter is also measured in millimeters
Terms for Astigmatism
Astigmatism is a defect in the eye caused by a deviation from spherical curvature, which results in distorted images.
- Axis - ranging from 0 to 180 degrees, the axis determines the angle of correction needed for you to see clearly if you suffer from astigmatism
- Cylinder - the cylinder power of a lens measures the degree to which a lens must account for astigmatism. This measurement is preceded by a minus sign (much like power) and is written separately from the sphere power.
Terms for Presbyopia
Presbyopia is a normal degradation of your eyes' ability to focus on near objects that is brought on by age
- Addition (ADD) - if presbyopia is affecting your near vision, this figure determines the level of correction you need in order to be able to see clearly at a close distance
- Dominant - for those with multi-focals or bifocals, lens correction requires designation of a dominant and nondominant eye. The dominant eye (D) prioritizes distant vision while the nondominant eye (N) prioritizes near vision.
Finding Your Brand
Choosing the right brand of contact for you is all about personal preference. When selecting a brand, it's important to take in the replacement schedule (daily contacts vs. weekly or monthly), color options available, and, most importantly, the feel.