6 Things to Know About Reading Your Eye Prescription

Woman trying on eyeglasses.

Regular eye exams are essential to keep your eyes and vision healthy. During the appointment, vision tests help the doctor determine if your vision is 20/20, and also detect signs of eye diseases and medical conditions. You will be asked to read a combination of numbers and letters in different sizes to check how well you see. At the end of the visit, you may receive a prescription to enhance your vision. Because many people find the numbers and words confusing, here’s how to read your eye prescription.

  1. + or – numbers

    A positive prescription number, such as +1.50, indicates the strength needed to help correct farsightedness. People with farsightedness can see things far away, but close-up objects can be blurry, making it hard to read.

    A negative number, like -1.50, shows that you need correction for shortsightedness. You probably can see close-up objects clearly, but people and things in the distance are blurry.

    Tip: Eyeglass and contact lens prescriptions are different. Eyeglass lenses sit farther away from your eyes. Contact lenses sit directly on top of your eyes. Think about which you prefer.

  1. Number size

    A prescription number of +1.00 or -1.00 indicates that a minimal prescription change is needed. In comparison, +4.00 or -4.00 means you need a stronger prescription to see clearly.If you notice changes in your vision, such as difficulty reading signs or seeing objects clearly, contact your eye doctor for an eye exam. You may be surprised how much better you can see with vision correction.

  1. OS vs. OD

    OS stands for oculus sinister and refers to the left eye. OD means ocular dexter, representing the right eye.

  1. Spherical correction (SPH)

    The first number in the prescription is called SPH. It refers to the lens strength needed to correct vision for the whole eye.

  1. Cylindrical correction (CYL)

    This is the second number in the prescription, and it indicates a correction needed for astigmatism. People with astigmatism have an irregularly shaped cornea that causes blurry vision. It’s a common eye condition that impacts millions of Americans.

  1. Special correction needs

    When reading an eye prescription, sometimes there are specialty words. ADD refers to the vision strength the lens maker needs to add to help magnify objects, such as the lower half of bifocals for reading. AXIS shows where the lens maker should make the astigmatism correction in the lens. PRISM means the lens maker needs to add a prism in the lens to help the eyes work better together.

Want to enjoy a lifetime of good vision? Take these steps to protect your eyes. And if you need vision correction, be sure to choose the lenses that work best for your lifestyle.


All About Vision
American Academy of Ophthalmology