How to Read an Eye Prescription: What the Numbers Mean (2024)
Regular eye exams are an important part of keeping your eyes healthy and your vision sharp.
At your eye exam, an eye doctor, optometrist, or ophthalmologist, will check for any signs of eye disease. If your vision needs to be corrected, you’ll be given a prescription for eyeglasses or contact lenses.
Eye prescriptions can be hard to decipher, though. They usually contain an assortment of numbers and letters that can be confusing if you don’t know what they mean.
This article will help make sense of the abbreviations and numbers that may be included in your eye prescription. It will also explain how prescriptions can vary depending on your vision issue.
Your eyeglass or contact lens prescription will contain various abbreviations, many of which will be followed by numbers.
Here’s a summary of what these abbreviations mean:
A glossary of eye prescription abbreviations
ADD stands for the additional lens power needed to make it easier for you to read. This number is seen on prescriptions for reading glasses or the lower portion of bifocal or progressive lenses.
Axis is a number between 1 and 180. It indicates exactly where the astigmatism appears on your eye.
BO, BI, BU, BD stand for base out, base in, base up, and base down. These abbreviations tell the eyeglass manufacturer exactly where to position the prism on eyeglasses that correct double vision.
CYL stands for cylinder, or the amount of astigmatism in your eye. The cylinder and axis together help correct astigmatism.
DV is an abbreviation for distance vision. This number indicates whether you have nearsightedness or farsightedness.
NV stands for near vision, or the amount of power that needs to be added to make reading easier.
OD means oculus dexter, or your right eye.
OU stands for oculus uterque, or both eyes.
OS is oculus sinister, or your left eye.
PD means pupillary distance. Monocular PD is the distance from your pupil to the middle of your nose. Binocular PD is the distance from one of your pupils to the other pupil.
Prism is used if you have double vision. It indicates the amount of prismatic power your glasses need to correct for differences in the alignment of your eyes.
SPH means sphere, or the power of the lens that will correct your eyesight.
Many of the abbreviations on your prescription will be followed by numbers.
If the numbers are marked with a plus sign (+) or no sign, you’re farsighted. If the numbers are marked with a minus sign (-), you’re nearsighted.
Some of the numbers in your prescription tell the eyeglass manufacturer how much correction your vision needs. Eyeglass strength is measured in diopters.
If your prescription reads -1.00, that means your eyeglasses need 1 diopter of strength to correct nearsightedness.
If your prescription reads +2.50, your eyeglasses need 2.5 diopters of strength to correct farsightedness. The higher the number, the more correction your vision needs.
Nearsightedness, or myopia, is a common refractive disorder. If you’re nearsighted, you can see objects that are close clearly, but objects that are farther away will look blurry.
With nearsightedness, your eye is usually elongated, with too much distance between the cornea at the front of your eye and the retina at the back of your eye. Nearsightedness can also happen if the cornea of your eye is too curved.
Due to this increased distance, light rays fall in front of your retina (a light-sensitive structure that sends signals to your brain) instead of on it. This can cause your distance vision to be fuzzy.
The lenses in your eyeglasses will correct the bend in the light and help you see distant objects more clearly.
For a nearsighted prescription, the strength of the lenses will be marked with a minus sign. The more nearsighted you are, the higher the numbers will be.
For instance, a lens prescription of -5.00 is a stronger prescription than -2.00. The strength of the lenses can vary for each eye.
Farsightedness, or hyperopia, is a refractive disorder that makes close objects harder to see than distant objects. It happens because the distance from the cornea to the retina is too short or because the cornea of your eye is not curved enough.
If you’re farsighted, light focuses behind your retina instead of squarely on it.
For a farsighted prescription, the strength of the lenses will be marked with a plus sign. The more farsighted you are, the higher the numbers will be. For instance, a lens prescription of +4.50 is a stronger prescription than one that’s +2.00.
Correcting your vision with glasses or contact lenses, for both nearsightedness and farsightedness, may also help prevent:
Astigmatism is an irregular curve in either the lens or the cornea of your eye. This irregular curve can bend the light that enters your eye and affect the way it hits your retina. Astigmatism can blur both near and far objects. It can also distort the images you see.
If your astigmatism measures 1.5 diopters or more, you may need to wear prescription glasses or contact lenses to see properly. That said, if you have any amount of astigmatism, you may appreciate the extra clarity of wearing prescription eyewear.
Your prescription will indicate how severe your astigmatism is and where the irregular curve appears on your eye.
Your eyeglass prescription might also include notes from your optometrist or ophthalmologist about other features of your glasses or contacts. Your lenses might:
be progressive or bifocal, meaning they correct for both distance and close-up vision.
have an anti-reflective or anti-glare coating to reduce glare to make it easier to see at night or when working on a computer
be photochromic, which means they darken or lighten depending on the lighting conditions around you
be treated with a coating to make them more scratch-resistant
Yes. Because contact lenses sit directly on the surface of your eye, they need to have the same curves as your eye.
A contact lens prescription contains measurements for:
Base curve: a number usually between 8 and 10 that conforms to the shape of your eye
Diameter: the distance from one side of the lens to the other, usually around 13 to 15 millimeters
Your contact prescription also identifies the brand and type of lens, along with an expiration date. Contact prescriptions have to be updated from year to year to account for changes to your vision and to ensure they fit properly.
The American Optometric Association recommends that you have an eye exam at least every 2 years if you’re under 60 and every year if you’re over 60.
It’s important to have your vision and eye health checked regularly because some serious eye conditions, such as glaucoma, don’t have noticeable early symptoms.
An eye doctor can test your eyes and detect changes early, which may prevent vision loss. The tests are quick and painless, and can also help detect the following eye conditions:
cataracts
glaucoma
age-related macular degeneration
Eye exams can also indicate when another health condition, such as diabetes or high blood pressure, may be affecting the health of your eyes.
The abbreviations and numbers on your eyeglass prescription tell the eyeglass manufacturer what type of lenses you need and how strong they need to be. This information also indicates the degree of nearsightedness, farsightedness, or astigmatism in each of your eyes.
Because contact lenses sit directly on the surface of your eye, they need additional information, such as the base and curve of your eye.
Your eyeglass or contact lens prescription isn’t a one-and-done situation. Over time, your vision can change, so it’s important to see an eye doctor at least every couple of years to protect your eye health.
A minus sign before the number indicates that you are nearsighted, while a plus sign means that you're farsighted. Lens power is measured in diopters
diopters
A dioptra (sometimes also named dioptre or diopter, from Greek: διόπτρα) is a classical astronomical and surveying instrument, dating from the 3rd century BC. The dioptra was a sighting tube or, alternatively, a rod with a sight at both ends, attached to a stand.
. The higher the number, the stronger the prescription. For example, “-5.00” written under sphere means that you are very nearsighted and need a five diopter correction.
Sphere: The sphere (SPH) on your prescription indicates the lens power you need to see clearly. A minus (-) symbol next to this number means you're nearsighted, and a plus (+) symbol means the prescription is meant to correct farsightedness.
In general, the further away from zero the number on your prescription, the worse your eyesight and the more vision correction (stronger prescription) you need. A “plus” (+) sign in front of the number means you are farsighted, and a “minus” (-) sign means you are nearsighted.
For the farsighted, the AOA classifies it this way: If your number is between +0.25 and +2.00, you have mild farsightedness. If your number is between +2.25 and +5.00, you have moderate farsightedness. If your number is greater than +5.00, you have high farsightedness.
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.
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. Generally, eyes with 1.5 diopters of astigmatism or more require correction.
Astigmatism is measured in diopters. A perfect eye with no astigmatism has 0 diopters. Most people have between 0.5 to 0.75 diopters of astigmatism. People with a measurement of 1.5 or more typically need contacts or eyeglasses to have clear vision.
Line 1: If you are only able to read the big E, your vision is approximately 20/200. If you can read the T & B, you are reading 20/100. Line 2: This line is approximately 20/50. Line 3: This line is ~ 20/40.
Patient's name and another identifier, usually date of birth. Medication and strength, amount to be taken, route by which it is to be taken, and frequency. Amount to be given at the pharmacy and number of refills. Signature and physician identifiers like NPI or DEA numbers.
Visual acuity less than 20/200 is considered legally blind, but to actually fit the definition, the person must not be able to attain 20/200 vision even with prescription eyewear. Many people who would be legally blind without eyewear can function well in everyday life with appropriate glasses or contact lenses.
+1.75: spherical power (positive) indicates hyperopia. +1.25 x 135: cylindrical lens of positive power with axis at 135 degrees, for correction of astigmatism. Add: +1.50 means this prescription includes a bifocal application for reading. PD: the distance from the center each pupil to pupil is 62 millimeters.
If you have a minus number, like -2.75, it means you're short-sighted and find it more difficult to focus on distant objects. A plus number indicates long-sightedness, so objects up close appear more blurred or close vision is more tiring on the eyes.
When you have astigmatism, some of the bold lines will look blurrier than others.It may look like some are drawn with a black marker and others are faded. That's because the abnormal curve of your eye makes parts of a picture more or less clear.
Blurred vision is the most common astigmatism symptom. It also makes it hard to see details on objects, like the words printed on a menu in front of you, or letters on a road sign in the distance. Other astigmatism symptoms include: Seeing a glare or halos around lights.
What causes astigmatism? Astigmatism happens when your cornea or lens has a different shape than normal. The shape makes light bend differently as it enters your eye, causing a refractive error. Doctors don't know what causes astigmatism, and there's no way to prevent it.
Astigmatism frequently worsens with age. Your cornea can become more irregular due to pressure from your eyelids as they lose muscle tone. Astigmatism generally stays stable until your turn 50.
20/20 vision is normal vision acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at a distance.
20/30 to 20/60, this is considered mild vision loss, or near-normal vision. 20/70 to 20/160, this is considered moderate visual impairment, or moderate low vision. 20/200 or worse, this is considered severe visual impairment, or severe low vision.
Having 20/20 vision means that your vision is normal. If you don't have 20/20 vision, your eye care professional will help you find out what condition may be affecting your vision. They'll also help you find a way to improve your vision, such as wearing glasses or having eye surgery.
With correction, about 75% of adults have 20/20 vision. In most states, you need 20/40 vision or better for an unrestricted driver's license. People are “legally blind” if their vision with glasses or contacts is 20/200 or worse.
What is 20/80 Vision? Doctor Moosa of Excel Laser Vision Institute, a LASIK eye center in Los Angeles, explains that when a person has 20/80 vision, the individual's eyesight is already in the low vision range. 20/80 is an average visual impairment as regulated by the International Council of Ophthalmology (ICO).
If you have 20/30 vision, that means what you see comfortably at 20 feet, can be seen by a person with "normal" vision at 30 feet. Your vision is weaker, in other words.
An Rx number or prescription number is a number that the pharmacy uses to reference your specific prescription. This number can help your pharmacist quickly find your prescription information to fulfill refills or answer questions.
If you have a high negative prescription, you'll be familiar with thin lens options which are made from high index materials. The higher the index number, the thinner your lenses will be. These materials essentially have an ability to bend light into your eyes at a higher angle which in turn corrects your sight.
Since being legally blind is determined by visual acuity and field of vision, this generally means that those with a prescription of -2.5 or lower in either or both eyes are considered legally blind.
In order to be legally blind, you must have a visual acuity of 20/200. This means that even with glasses or contacts, you can only read the first letter at the top of the Snellen Chart, if that. You can also be legally blind if you can see, but only in a very small window in your eye.
So +1.00 and -1.00 are quite modest; your eyesight isn't too bad, as you only need 1 diopter of correction. On the other hand, +4.50 and -4.50 represent a greater lack of clarity; you'll need a stronger prescription, at 4.5 diopters of correction.
If you're legally blind, your vision is 20/200 or less in your better eye or your field of vision is less than 20 degrees. That means if an object is 200 feet away, you have to stand 20 feet from it in order to see it clearly.
The highest level of corrective power for monthly soft contact lenses is about -12 Dioptres (bear in mind that the average prescription for short sighted people is -2.00 Dioptres), and is available from both Purevision 2HD and Biofinity.
A -5 eye and a -7 eye are not much differently at risk, but both are significantly more at risk of retinal problems than a more normal, non-myopic eye. These are rare, though, so no cause for alarm.
If your prescription reads +2.50, your eyeglasses need 2.5 diopters of strength to correct farsightedness. The higher the number, the more correction your vision needs.
3.75 vision is equivalent to 20/530 visual acuity. This means that a person with 3.75 vision can read letters from 20 feet away that a person with normal vision can read from 530 feet away.
Typically, objects close to your eyes seem clear, and those that are far away appear blurry. If your prescription reads -2.00, that means you are two diopters nearsighted. If your prescription said +3.50, you are three and a half diopters farsighted.
The lowest-strength reading glasses have powers of +0.25 diopters, whereas high-strength ones can go well beyond +2.50 diopters—in rare cases, all the way up to +4.00. When you need reading glasses beyond +2.75 diopters or so, you may have to get them custom ordered.
The former represents correction for nearsightedness (difficulty seeing far away) and the latter represents correction for farsightedness (difficulty seeing close by). So, a prescription could be -3.75 meaning that the lens needs to provide three and three-quarter diopters of correction for nearsightedness.
If you're interested in cutoffs between moderate and severe kinds of vision issues, we can tell you that nearsightedness needing a refractive correction of -5 diopters or more is often considered “high myopia,” whereas a prescription reading +5.25 diopters fits the bill for “high hyperopia.” However, these scales can ...
The larger the number, the larger the correction that's needed. When you look over your prescription, if you see smaller values like +/- .25, you can see that this part of your vision needs some correction. Larger values like +/- 5, indicate that a good deal more correction is needed for this part of your vision.
-3.75 vision is considered moderate to high myopia. It means that you can see objects clearly up to a distance of about 13 inches, but anything beyond that will appear blurry. This can make it difficult to perform everyday tasks such as driving, watching TV, or reading road signs.
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.
A plus sign (+) indicates farsightedness, while a minus sign (-) means that you're nearsighted. How nearsighted or farsighted you are is indicated by the numbers: as a rule, the further away the number is from zero, the worse your vision and the higher your requirement for vision correction.
Based on visual acuity testing, a person is considered legally blind when their best corrected vision is 20/200, which means they need to be at least 20 feet away to see something that a person with normal vision can see from 200 feet away.
A value up to 2.50 is considered moderate; anything above 2.50 may be considered severe. The third number (axis) reflects the orientation of your astigmatism.
What Do the Numbers Mean? The term 20/20 means that you can see an object clearly when it's 20 feet away from you, just like normal. If your vision is 20/100, then viewing an object from 100 feet away is too far for you but fine for others; to see it clearly, you must come within 20 feet of that object.
A visual acuity of 20/300 means that you can see at 20 feet what a person with normal vision can see at 300 feet. In other words, your vision is severely impaired. This level of visual acuity is considered legally blind in the United States.
Visual acuity less than 20/200 is considered legally blind, but to actually fit the definition, the person must not be able to attain 20/200 vision even with prescription eyewear. Many people who would be legally blind without eyewear can function well in everyday life with appropriate glasses or contact lenses.
What prescription is considered legally blind? Legal blindness is defined as 20/200 vision. 14 The prescription equivalent is -2.5. It is important to note that prescriptions for corrective lenses are different for each person, and measurements can be different for each eye.
The maximum negative eye power is typically around -20 diopters. This means that if you have myopia of -20 diopters, you will need to wear glasses or contact lenses with a power of -20 in order to see clearly.
Lights with astigmatism are well-known for appearing fuzzy, streaky, or encircled by haloes, particularly at night. The lights seem that way because of the distorted cornea, which hinders adequate light intake in your eyes, causing the lights to scatter.
The next number in the sample prescription is -0.50. This is the "cylinder" measurement. On your prescription, "cylinder" might be abbreviated as "CYL." The cylinder measures the degree of astigmatism in your eye. The number shows how much lens power will be needed to correct astigmatism.
If your prescription reads -1.00, that means your eyeglasses need 1 diopter of strength to correct nearsightedness. If your prescription reads +2.50, your eyeglasses need 2.5 diopters of strength to correct farsightedness. The higher the number, the more correction your vision needs.
A 1.25 eye prescription means you need 1.25 diopters to correct your vision problem. This prescription is considered relatively mild, and you usually don't need corrective eyewear for it.
Does Someone With 20/40 Vision Need Glasses? Some people with 20/40 vision choose not to wear glasses or contacts, but prescription lenses will almost certainly help them if they want to improve their visual acuity.
A visual acuity of 20/20 is considered normal. If you have 30 40 vision, it means that you can only read the letters from a distance of 30 feet that someone with normal vision can read from 40 feet away.
Introduction: My name is Margart Wisoky, I am a gorgeous, shiny, successful, beautiful, adventurous, excited, pleasant person who loves writing and wants to share my knowledge and understanding with you.
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