If you've ever hadeyeglasses you’re familiar with the odd series of letters and numbers that make up your prescription. We know these as the instructions for making your glasses, but what do they actually mean? Here’s a quick summary:
Which numbers are my right eye and which are my left eye on my prescription?
In a typical prescription, two acronyms—one for each eye—are listed:
- O.D. This is short for oculus dexter, and is your right eye
- O.S. This is short for oculus sinister, and is your left eye
What does “sphere (SPH)” mean on my prescription?
The sphere column is often abbreviated as SPH. This is the lens power needed to fix your vision. A minus sign (−) next to the number means nearsightedness (you see better up close and need distance correction). A plus sign (₊) indicates you are farsighted (you see better far away and need your near vision corrected).
Lens power is measured in diopters, so you may see thesphere field abovewritten as −9.00 D—this means there are 9 diopters of nearsightedness. Think of the measuring system as an integer number line, with zero in the middle needing no correction. The further away you get from the zero on either the minus or plus side, the stronger your prescription is.
Trial lenses used for checking a person's glasses prescription
What is the “cylinder (CYL)” number on my prescription?
The cylinder number is how muchastigmatism you have, if any. This is when part of thecornea has a different curve. Normally, an eye is shaped like a basketball—rotated any direction, the curve stays the same. An eye with astigmatism is oval- or egg-shaped, or more like a North American football—one curve is longer than the other. The CYL number corrects this different second curve.
Axis
This number tells you where the astigmatism is on the cornea. The axis—written in degrees between 1 and 180—indicates which way the astigmatism lines up.
Add
There is where any additional lens powers are written. For example, some people over age 40 don’t want an extra pair of glasses for reading. They choose to wear bifocals instead. The lower half of the lens gives them their reading vision.
Where is the lens power for prism on my prescription?
There may be a field forprism on the right side (not pictured). This is a special type of correction built into the lens for some people withdouble vision (seeing two separate images of the same object). The prism fuses the two images together so only one image is seen.
What about contact lenses?
Because contacts sit directly on the eye, the prescription is different than one for eyeglasses. A contact lens prescription includes measurements specific to the size and brand of your contacts. Before filling a prescription, you also need what’s called a “contact lens fitting” to see if they’re right for you.
FAQs
The sphere column is often abbreviated as SPH. This is the lens power needed to fix your vision. A minus sign (−) next to the number means nearsightedness (you see better up close and need distance correction). A plus sign (₊) indicates you are farsighted (you see better far away and need your near vision corrected).
What do prescription glasses numbers mean? ›
An example would be if your prescription shows a reading of -1.00, it means that you have one diopter of nearsightedness. The larger this number gets, the more severe the nearsightedness is. In addition to the intensity of the diopter measurement, these numbers will also determine how thick your lenses need to be.
What is a normal cyl in eye prescription? ›
Cylinder: For this astigmatism value, the value will usually be between +/-0.25 to +/-4.00. These numbers tell eye care specialists how cylindrical your lenses should be to which focuses light into a line instead of a point. Axis: For this additional astigmatism value, the value ranges between 1 and 180.
How do you read a 20 20 eyeglass prescription? ›
The second number is the smallest line of letters that a patient can read. In other words, 20/20 vision means that at a 20-foot test distance, the person can read the 20/20 line of letters.
Can you figure out your own glasses prescription? ›
Remember to request your prescription details from the office where you last had an eye exam. They're required to share a copy with you. If you're looking for other options to find out your prescription based on existing glasses, there are other scanning apps like the one GlassesUSA offers.
What is the format for eye prescription? ›
An example of an eyeglass prescription
Here is a sample eyeglass prescription: OD -2.00 SPH +2.00 add 0.5 p.d. OS -1.00 -0.50 x 180 +2.00 add 0.5 p.d. In this case, the eye doctor has prescribed -2.00 D sphere for the correction of myopia in the right eye (OD).
How do you read eyeglass numbers? ›
Use 54-16-140 as an example. The first number, 54, represents the lens width; the second number, 16, refers to the bridge size, while the last number, 140, is the temple length.
What are the 3 sets of numbers on glasses? ›
You'll find up to three numbers on glasses frames, and they stand for the lens width, bridge width, and temple length. These numbers are written on the inside of one arm and may be separated by spaces or dashes. Often, a small square shape separates the lens width from the bridge width.
What is a bad astigmatism number? ›
75 diopters of astigmatism, and this is considered normal and will likely not require correction. Between . 75 and 2 diopters is considered mild astigmatism. Between 2 and 4 diopters is moderate astigmatism, and 4 or more diopters is considered significant or “bad” astigmatism.
At what prescription should you wear glasses all the time? ›
The moderate to high myope
Your glasses prescription is around -3.00 to -6.00. Now most of these people will wear there glasses all the time because anything past 20-33 cm is out of focus.
For example, a prescription of -1.25 is mild myopia, whereas +6.00 is high hyperopia. 'Bad' eyesight, or rather a stronger prescription, would be any number above -5.00 or +5.00. This means that your vision is more impaired than someone with a lower prescription.
What is considered a strong eye prescription? ›
Before we jump into what each section of how to read an eye prescription means, as a general rule, the higher the numbers on your prescription, the worse your eyesight is and the stronger your prescription will be to provide the necessary correction. Mild: -0.50 to -3. Moderate: -3.25 to -5.00. High: -5.25 to -10.
What does astigmatism look like? ›
Astigmatism is the medical term that means the shape of your eye is more curved than it should be. It's a type of refractive error — an extremely common eye condition that causes blurred vision. Usually, eyes are round, like a baseball. If you have astigmatism, your eye is shaped like a football or the back of a spoon.
What does a perfect eye prescription look like? ›
The Snellen Chart for Vision Testing
Someone with perfect vision (20/20) would be able to see the same line of letter from 20 feet away that a normal person sees at 20 feet away. However, someone with 20/40 vision sees at 20 feet away what a normal person sees at 40 feet away.
How to read prescription on glasses frame? ›
The number under the sphere column determines the strength of correction you'll need. The further the number is from 0, the worse your eyesight is and the stronger your prescription will be. In front of the number will either be a minus sign (-) or a plus sign (+).
How do you read reading glasses numbers? ›
A negative number represents nearsightedness, while a positive number means farsightedness. The higher the number of diopters, the stronger the power of the glasses. That means +1.50 diopters are stronger than +1.00 diopters. Or, put another way, the higher the number, the closer you'll be able to see.
What does 1.75 mean for glasses? ›
Let's start with -1.75. A -1.75 eyewear prescription essentially signifies that you need some additional power to see some objects that are further away. Specifically, we are talking about things like watching television or objects or people at a distance when you are driving.
How do you convert prescription to reading glasses? ›
Reader Strength = SPH + ADD
To calculate your reader strength, take your SPH and add the ADD. For example, if the SPH is +1.00 and the ADD is +1.75 for the right eye, the strength of the reader lenses would be +2.75 for that eye. And if the SPH were -1.00 instead, you'd be looking at a +0.75 reader strength.
What do the 3 numbers on glasses mean? ›
What Do the Numbers on Glasses Mean? Glasses Measurements. Close. You'll find up to three numbers on glasses frames, and they stand for the lens width, bridge width, and temple length. These numbers are written on the inside of one arm and may be separated by spaces or dashes.
