Simple Guide: How to Read an Optometrist Prescription

If you’ve ever looked at your optometrist prescription and felt like you were trying to decode a secret message, I’m here to help. 

I know all the letters, symbols, and numbers can be confusing at first, but they are easy to understand once you know how to break them down.

optometrist showing client patient results

Head optometrist showing client results


How To Read Glasses Prescription:

Here is a simple guide to reading an optometrist prescription so you know what to expect when shopping for contact lenses or glasses. 

Quick Summary: How do you read a glasses prescription? 

  • The numbers and abbreviations on your eyeglass prescription indicate how strong the lenses must be and the type of lenses required to treat your eye condition 
  • Generally, your right eye and your left eye will each have their own prescription
    • The information on an optometrist prescription details the degree of eye conditions, such as astigmatism, nearsightedness, and farsightedness for each eye  
    • Because contact lenses require a different prescription since they are worn directly on the eye’s surface and must match the specific curve of your eye 
  • Eye testing is quick, comfortable, and one of the most effective ways to take care of your eye health
  • Your vision can change over time, making it important to see your eye doctor for regular checkups and eye testing to ensure your prescription is still appropriate


What Is an Optometrist Prescription? 

An optometrist prescription is a written order that specifies the parameters required to correct an individual’s vision. An eyeglass prescription will typically specify the lens power needed, which eye the prescription is for, and other necessary details. 

An optricin will use the optometrist prescription to make and fit corrective lenses to help you see easier and more clearly. 


How to Read an Optometrist Prescription 

Here are some of the common abbreviations and numbers you’ll see on an optometrist prescription and what they mean:

  • OD — OD refers to oculus dexter, or the right eye. This number shows your right eye’s specific needs. 
  • OS — OS refers to oculus sinister, or the left eye. This indicates a prescription is for your left eye.
  • OU — Seeing “OU” (oculus uterque) on an eyeglass prescription isn’t common. OU indicates that a prescription applies to both the right and left eye. 
  • Sphere (SPH) — SPH refers to the sphere value. This signifies the main refractive correction your eye needs. Simply put, it indicates how much lens power is needed to correct your eyesight. If there is a minus sign, this signifies myopia (nearsightedness). A plus sign indicates hyperopia (farsightedness). 
  • Cylinder (CYL) — A cylinder value (CYL) will be listed if you have astigmatism. CYL indicates your eye’s degree of astigmatism.
  • Axis — The axis will be listed along with the cylinder value, so you will only see this if you have astigmatism. The axis will be listed between 1 and 180 degrees. This number specifies where the astigmatism is located in your eye. 
  • Prism — If you have double vision, you may see ‘Prism’ listed on your optometrist prescription. This signifies how much prismatic power is needed to correct your eye’s alignment. It also gives the optician details on how to position the prism on the eyeglasses to correct the alignment and help your eyes work together properly.  

The base direction will be listed as: BU (Base Up for vertical alignment issues), BO (Base Out, away from the nose, for horizontal alignment issues), BI (Base In, toward the nose, for horizontal alignment issues), or BD (Base Down for vertical alignment issues) 

  • ADD — ADD is short for Additional Lens Power. This indicated the additional magnifying power needed for activities that require near vision, such as using a laptop or reading. This is always a positive value that applies to both eyes.  
  • DV — DV is short for distance vision. This indicates that you have farsightedness.
  • NV — NV is short for near vision. This specifies how much lens power is needed to make near-vision activities, such as reading, easier for you. 
  • PD — PD stands for pupillary distance. Monocular PD refers to the distance between the middle of your nose and your pupil. The distance between your pupils is referred to as binocular PD. Disclaimer: The PD measurements are taken by the dispensing optician for each eyewear and by the suppliers of the eyewear. PD measurements are specific to the optical frame that best fits you and monocular heights are measured accordingly to ensure the best optics in your new eyewear.


How to Read a Contact Lens Prescription

Prescriptions for glasses and contact lenses are completely different. Contact lenses are worn directly on the eye’s surface, making it crucial for the lenses to match the curve of your eye. 

Contact lens prescriptions contain measurements for the base curve of the eye (BC), the diameter of the eye (DIA), and the type and brand of contact lenses that match your requirements. The prescription will also include an expiration date.

Opting for glasses or contacts should be a decision based on personal preference and lifestyle.

What Gives an Optometrist This Information? 

Determining a prescription is a complicated, intricate process involving clinical expertise, various tests and assessments, and state-of-the-art technology. Our Perth optometrists use advanced diagnostics to perform comprehensive eye testing. 

We take a ‘big picture’ approach to ensure we identify the ideal treatment for your eye conditions and needs. We evaluate medical and family history, ocular motility, colour vision, and visual acuity to tailor a treatment plan to your exact vision issues. Along with developing prescriptions for glasses or contact lenses, eye testing is a crucial tool for detecting underlying eye conditions. Eye tests are quick, comfortable, and one of the most effective ways to take care of your eye health.

These eye exams are important because certain eye conditions start without symptoms, allowing the condition to progress. Without early detection, eye conditions such as glaucoma can become more serious. Our eye testing can reveal serious eye conditions that may not be showing symptoms yet to ensure early diagnosis and treatment. We also diagnose myopia, hyperopia, astigmatism, and other eye conditions. 

It is recommended to have an eye exam every 2 to 3 years if you are over age 40. Your optometrist may recommend more frequent testing if you have the following risk factors:  

  • A family history of eye conditions diabetes
  • Diabetes
  • Over age 65
  • High blood pressure

(Source: Health Direct Australia)

Schedule Your Comprehensive Eye Test Today

The numbers and abbreviations on your eyeglass prescription indicate important information about the type of eye condition, how strong the lenses must be to correct it, and which eye it is for. Once you know what the abbreviations stand for, it is easier to read an optometrist prescription and understand what it means. 

If you’ve searched “optometrist Perth” and wondered who to choose, our team at The E Eye Place is ready to help you enjoy healthy eyes and your best vision. Discover your best vision and healthiest by booking an appointment with our caring, experienced team of optometrists. 

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