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How to Read Your Contact Lens Prescription

How to Read Your Contact Lens Prescription

It is important to be able to read your contact lens prescription for several reasons. First and foremost, the prescription is your guide for knowing what lenses you need to wear to achieve clear vision. Just like eyeglasses, contact lenses are customized to address specific vision issues, such as nearsightedness, farsightedness, astigmatism or presbyopia. Ignoring or misinterpreting your prescription and wearing the wrong kind of lenses can result in discomfort and eye strain. 


However, experiencing some discomfort initially does not mean that you are wearing the wrong prescription. It is common for first time wearers to experience some negative symptoms but these symptoms usually disappear after a week or two. Read our blog post on 7 Tips on Getting Used to Your Contact Lenses to learn more about how you can adjust to your new lenses. 

What is the Difference between Eyeglass and Contact Lens Prescription?

The primary difference between eyeglass and contact lens prescriptions lies in the specific details tailored to each method of vision correction. Eyeglass prescriptions typically include information for each eye, specifying the lens power needed to correct various vision problems. The prescription also indicates the lens design, such as bifocal or progressive lenses. On the other hand, contact lens prescriptions provide additional details crucial for fitting lenses directly onto the eyes. This includes the base curve, diameter, and sometimes the brand or material of the contact lenses. 

Demystifying the Abbreviations on the Contact Prescription 

hand with contact lens

Ever wondered what those seemingly random abbreviations and numbers on the prescription mean? These letters and numbers are the key to understanding your prescription and knowing what they mean will allow you to understand the contact lenses you need. 

Here is your guide to demystifying the meaning of your prescription:

OD: Oculus Dexter / Right Eye 

OS: Oculus Sinister / Left Eye 

DIA: DIA stands for diameter which refers to the width of your contact lens 

 

BC: BC stands for Base Curve which refers to the curvature of your contact lens. Contacts from some brands come in only one base curve whereas some other brands may have a number of different base curves. 


CYL: CYL stands for cylinder. This applied to individuals with astigmatism who require a cylindrical lens, not a spherical one.


AXIS: Axis is measured in degrees and refers to the location of the astigmatism on the cornea.  


ADD: ADD stands for addition and refers to the additional magnifying power that is needed for close-up tasks. This is indicated by a number or may simply be denoted as low, medium, or high. 


D/N: D refers to the dominant eye and N refers to the non-dominant eye. This factor comes into play in multifocal and bifocal contacts where you have different levels of vision correction for each eye. 


Brand: This refers to the brand of contacts that your optometrist has prescribed for you. 


PWR or SPH: PWR or SPH stand for power or sphere and refer to the strength of your prescription denoted by a positive or negative number. 


Expiration Date: This refers to the expiration date of your prescription, that usually lasts for 1 or 2 years. 

Reading the Prescription on the Contact Lens Package

When you observe your contact lens package or box, you will notice some of these abbreviations on it. Make sure that your prescription and the information on the box correspond to each other in order to ensure that you have the right lenses. 

How to Read a Contact Lenses Prescription for Astigmatism 

Reading a contact lens prescription for astigmatism is not too complicated if you know what to look out for. If you have astigmatism, you will need to look out for the cylindrical value (abbreviated as CYL) and the axis (abbreviated as AXIS). 

The cylindrical value refers to the correction you need specifically for astigmatism and the axis refers to the orientation of the correction. Understanding these specifics ensures that the lenses are tailored to fit your eyes' shape, providing precise correction for astigmatism and helping you see the world more clearly.

How to Read a Contact Lenses Prescription for Presbyopia 

Individuals with presbyopia require multifocal lenses and have another set of factors they need to look out for. The design of multifocal lenses often includes a prescription for distance vision, intermediate vision, and near vision, all within one lens

When it comes to multifocal contacts, you will notice a figure denoting additional magnification (abbreviated as ADD) and sometimes a figure denoting the dominant and non-dominant eyes (abbreviated as D/N).

Why is it Important to Understand Your Contact Lens Prescription?

Understanding your prescription is the first step to correcting your vision. Although your optometrist or a pharmacist can explain your prescription, it is helpful to know what kind of correction you need and what kind of lenses you need to purchase. Knowing what your prescription means will empower you with the knowledge to make the right choices for the sake of your vision.