How to Read an Eyeglasses Prescription
Author: Ian C. Langtree - Writer/Editor for Disabled World (DW)
Published: 2010/05/23 - Updated: 2026/05/08
Publication Type: Informative
Category Topic: Visual Aids - Related Publications
Contents: Synopsis - Introduction - Main - Insights, Updates
Synopsis: This information explains how to interpret each section of a written eyeglasses prescription so the reader can verify lens accuracy, order corrective eyewear online with confidence, and track changes in vision over time. The article walks through every standard notation an optician records after an eye test, including the SPH (sphere) value that sets prescription strength in 0.25 increments, the CYL (cylinder) and AXIS readings used for astigmatism, the ADD or near-addition figure for reading and intermediate lenses, plus optional notes covering BALANCE, PRISMS for squint or lazy eye correction, and pupillary distance (PD). The breakdown is particularly practical for seniors, people with low vision, and anyone with a disability who relies on accurate refractive correction to read, work at a computer, or move safely through daily tasks - Disabled World (DW).
- Topic Definition: Eyeglasses Prescription
An eyeglasses prescription is a written order issued by a qualified optician, optometrist, or ophthalmologist following an eye examination, specifying the exact optical correction required for each eye to address refractive errors such as myopia, hyperopia, astigmatism, and presbyopia. It records standardized measurements - sphere (SPH), cylinder (CYL), axis, near addition (ADD), and where relevant prism and pupillary distance (PD) - so that any qualified lens maker, whether in-store or online, can produce eyewear that matches the wearer's visual needs.
Introduction
Over time you might discover that you need a pair of prescription eyeglasses.
The first step is to always book an eye test with your local optician, which at its end you'll be given your prescription. Understanding your prescription will enable you to custom order the right lenses (if bought online), to better understand your eye health and to compare changes over time.
Main Content
To help you get to grips with your prescription, this guide will take you through the various parts. Your prescription will generally look something like this:
SPH
All prescriptions have SPH or SPHERE figure. This indicates the strength of your prescription in 0.25 increments. SPH beyond +/-8 is considered very strong prescription which will require extra special fitting by your optician.
CYL
If you have a common condition called Astigmatism, this figure is required. Also known as CYLINDER figure, it should be between +/-4 in 0.25 increments. In some cases opticians write 'DS' in the CYL column. This simply means there is no astigmatism.
AXIS
If your prescription has a CYL reading then it should have an AXIS reading between 0-180. It is important to note that not all prescriptions have CYL/AXIS values and and you may have it written down for one eye only.
ADD or NEAR ADDITION
The addition value is the amount to add to the SPH value for reading or intermediate glasses and sometimes for computer work. You might find this value outside of the ADD box in some cases. Opticians often write this figure all over the prescription, sometimes once (same for both eyes) sometimes once for each eye.
BALANCE (Optional)
This note is written when there is little or no vision in one eye, and the optician wants to make sure that the lenses match weight and thickness for cosmetic reasons.
PRISMS (Optional)
Prisms are used in eyeglasses generally when people have a slight squint or lazy eye by changing the way light is directed. The prism relieves strain by letting your eyes use a position that is more natural and comfortable.
PUPILLARY DISTANCE/PD (Optional)
This figure measures the distance between your eyes so that the center of each lens is aligned with the center of the your pupils.
Insights, Analysis, and Developments
Editorial Note: Eyeglasses prescriptions can look like a string of cryptic codes, yet each abbreviation carries specific clinical meaning that affects how clearly a wearer sees the world - making prescription literacy a small but meaningful step toward better self-advocacy in eye care. Readers who notice steady changes in their SPH, CYL or ADD values across successive eye tests should keep those copies on file, since the trend lines often tell an optometrist or ophthalmologist as much as a single appointment can, and they remain useful when ordering replacement lenses, comparing online retailers, or discussing options for low vision aids and assistive eyewear - Disabled World (DW).
Author Credentials: Ian is the founder and Editor-in-Chief of Disabled World, a leading resource for news and information on disability issues. With a global perspective shaped by years of travel and lived experience, Ian is a committed proponent of the Social Model of Disability-a transformative framework developed by disabled activists in the 1970s that emphasizes dismantling societal barriers rather than focusing solely on individual impairments. His work reflects a deep commitment to disability rights, accessibility, and social inclusion. To learn more about Ian's background, expertise, and accomplishments, visit his full biography.