Eyeglasses Prescription

eyeglass prescription


What is Eyeglasses Prescription?

There is no detailed information in your eyeglasses prescription about your spectacles. How well you would be able to see better with the left eye than the right and fluid pressure of the eyes. It indicates either your risk of glaucoma or if you already have glaucoma it indicates the efficiency of your treatment.


Have you ever been curious to know what the number and letters mean for your eyesight? By decoding your eyeglasses prescription in order to get a better understanding of what happening with your vision like knowing about what is going on with your vision.

Eye Power

The numbers you see written in your eye prescription under some abbreviations like OD, OS, and SPH determine your eye power. This number ranges from (+/-) 0 to 20. 0 means you don’t need a lens and your eyesight is normal, but if the numbers move away from zero then you’ll need artificial eye lenses/glasses to see perfectly.

When you look at your eye power prescription you’ll see abbreviations such as OS (oculus sinister) i.e. your left eye, OD (oculus dextrus) i.e. your right eye, and OU (oculus uterque) which means both the eyes. These are Latin abbreviations still used for the prescription. Some other elements like axis, astigmatism, and prism are also mentioned in the description. Numbers written under these abbreviations represent your eye power. Diopter is the unit of eyesight abbreviated as D. For example +1.5 D means you have hypermetropia with 1.5 eye power. -2.5 D represents myopia with 2.5 eye power.


How To Read Your Eyeglasses Prescription?

Your eyeglasses prescription includes a series of numbers. It usually in the chart and those series number helps us to create lenses that will perfectly correct your vision. The prescription charts typically have two rows. The first for the right eye and the other one is for the left eye. Moreover, there are five columns that are used to precisely describe your prescription.

Things you may have noticed that when you look at your prescription there are a bunch of abbreviations are given. Here are some following guides to help you to decode your eyeglasses prescription.


What are OD and OS

Glasses Prescription

They are abbreviations of “Oculus Dexter” and “Oculus Sinister”. These are the Latin terms for the right and left eyes. The OD indicates your right eye’s parameters and OS shows your left eye’s parameters.

Nowadays, these abbreviations are common in being replaced by “RT” and “LT” because they’re easier to decipher (Right eye and left eye, respectively).


Parts of Your Eyeglasses Prescription

At the top of your prescription, you will see some additional abbreviations like PWH or SPH, CYL, AXIS, ADD, Prism, and Base. This represents the measurement of detailed aspects of your prescription. Let’s know details about all abbreviations to gain more insight.

  • Refractive power (PWD) or Sphere (SPH):

This designates the amount of lens power that is needed in order to correct your nearsighted or farsighted vision. You had also noticed that there is a plus ‘+’ or minus ‘-‘ sign in front of the number that indicates that you are nearsighted/myopia (-) or farsighted/hyperopic (+). The larger the number following +/- the stronger the prescription.

  • Cylinder (CYL):

This indicates that you have a condition where the cornea or lens of the are irregularly shaped causing blurred vision (or Astigmatism). You may see a number listed that helps to determine the amount of lens power that is needed to correct astigmatism. In case, if you don’t see a number listed it’s a piece of good news that means you don’t have astigmatism.

  • AXIS:

It defines the direction of your astigmatism. This number usually ranges from 1 to 180.

  • Add Power(ADD):

It is the addictive power that represents the increase in magnifying power (measured in diopters with a plus sign) needed to correct for a prescription. The extra power added to your distance prescription in order to see clearly up close. If you require additional power, you have a condition called presbyopia. The number will always lead with a plus (+) and rang from +0.75 to +3.00.

This is known as the centres of each pupil (It is the black hole in the centre of the iris). It’s measured(which is measured in millimetres) is required to align the centre of the lens with the centre of the pupil, which is most important for proper fitting of lenses and visual comfort This number can be written binocularly (both the eyes) or monocular (one eye), and it varies when viewing at distance and near.

  • Prism:

It refers to the prismatic power which is used to correct vision displacement. It helps to reduce eye strain and correct double vision. It can be written as “p.d” or a superscript triangle when it’s written freehand.

  • Base:

It shows the direction of a prism by making the relative position of its densest edge. There are four abbreviations are used for prism direction (horizontal or vertical):

BU = base up

BD = base down

BI = base in (towards the wearer’s nose)

BO = base out (towards the wearer’s ear)

  • Segment Height (SH):

It is used to determine where to place the reading area on a multifocal correction lens. It is a frame-dependent measurement, which varies depending on who is wearing the frames.

  • Issue and Expiration Date:
Eyeglass’s prescription

In the law, Eyeglass’s prescription is valid for 3l24 months after the date of the prescription was written. When your prescription expires, you are not able to buy eyeglasses until your doctor writes an updated prescription. This will involve an eye exam to check your general eye health and refraction to determines your new prescription.


Additional Rx Information

Eyeglass prescription should include the name of the patient, the name of the prescriber, and the office’s contact information. You should understand your eyeglasses prescription. It helps you to make a smart decision if it comes to selecting the perfect frame and lens for your vision.

Eye Test

Your eye doctor may include the specific lens recommendation on your eyeglasses prescription like anti-reflective coating, blue light protection, or photochromic lenses. Which gives you the most comfortable vision correction possible.

It is important to know that contact lenses and eyeglass prescriptions are not the same. You need a separate contact lens prescription in order to purchase contact lenses.


How To Calculate Reading Glasses From A Presentation?

Calculate Reading Glasses

Distance Rx + Near Addition = Reading Rx.

It maybe looks simple, but you’re adding the numbers algebraically.

Right(OD) = +1.29

Add (for near) = +2.00

Total reading= +3.29


Right(OD) = -1.00 -0.50 × 180

Add (for near) = +1.00

Total reading Plano = -0.50 ×180. In the second example, it shows that Plano replaces the “0” and it means no power.

To know more about it, you can easily visit our website Eyemantra. Our expert guides will provide a healthy diet chart for your eyes. If you are looking for other services like cataract surgery, Retina surgery or Ocuploplasty you can simply ring at +91-9711115191. Even you can simply mail us on  [email protected].


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