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How to Read Prescription for Glasses : Glasses Prescription Explained

How to Read Prescription for Glasses : Glasses Prescription Explained

Knowing how to read eyeglasses prescription turns helpful for you when you are shopping online for your prescription glasses. While many of us struggle with that piece of the paper that our optometrist handed over to us when visited for an eye test but it turns out to tell the state of your eyes and what problems you are facing. If you are also failing to read your prescription then don’t quit it yet just because there are too many numerical signs and medical stuff. You must know your eye condition as it helps you to find the right type of glasses and also be informed about your eye condition.

Buying eyewear has become so simple with the advent of the online marketplaces. Now, you do not have to rush from one high-end shop to the other to get your favourite pair as everything is available at the click of a button.  You can even book eye-test at home or eye test at work to get the prescription for glasses. With every facility being provided by online eyewear manufacturers while you sit relaxed at home without the trouble of stepping out of the house. By following some easy steps, you can place the order of your favourite pair of eyeglasses and get same day dispatch.

The only problem that many people face while placing an order at online purchase of eyeglasses is filling up details of the prescription. Although, it is very clear and easy to understand, however, there are still a few points of technicalities that may sound unknown to many. Therefore, many people end up filling either incorrect information of prescription or they simply upload the picture of prescription provided by the ophthalmologist or eye optician. 

So what are those terms and terminologies that are holding you from filling the prescription online? Here is the list of the vital terms that can help you understand how to read prescription for glasses as handed by the eye care practitioner or optometrist which you can fill easily online.

OD and OS

The OD and OS are abbreviations that stand for oculus dexter and oculus sinister. These are Latin terms which refer to ‘right eye’ and ‘left eye’. Apart from this, the prescription may have a column of ‘OU’ which is a Latin word oculus uterque and means "both eyes." 

Nowadays, some of the prescriptions do not use OD or OS. Instead, they use the words as the right eye and left eye itself. Generally, prescriptions have a column for OD/  right eye before OS/ left eye.


Sphere means the amount of power that is measured in diopters (D) which is required to correct myopia, hypermetropia and presbyopia. This is denoted by negative (-) and positive (+) sign. A plus sign is mentioned against the power that is required to treat farsightedness and presbyopia whereby the lenses are required to correct nearby vision disorder.  Whereas a minus sign is mentioned before the power lenses that are used to correct nearsightedness. 


When multifocal lenses such as bifocals and varifocals are used, this term ‘Ádd’ is used which means the power of the bottom part of the lenses which acts as reading glasses. This is required when a person suffers from hypermetropia or presbyopia along with the degree of myopia.  This column of ‘Ádd’ is denoted by a plus sign in the prescription for glasses.


A cylinder is referred for the power for astigmatism. Not every prescription has astigmatism power. It is written after the spherical symbol of minus or plus sign. In many cases, cylinder column is left blank which means there is no astigmatism power associated with the eyes.


Axis could be any degree from 0 to 180 which is used to define the orientation of the astigmatism degree.  This degree mentions the curvature where the astigmatism is occurring in the eyes and how much it is. The axis states the degree that helps in crafting the eyeglasses for correcting astigmatism.


Prism is referred to prismatic power which is measured in prism diopters i.e. “p.d.”. It is also denoted with a small triangle figure in the prescription for glasses, just like the shape of a prism. The prism powered glasses are used by people who have alignment problems.  A very small section of society suffers from this problem though.


Pupillary distance measures the distance between the centers of the eye’s pupils. This is required to measure the focus point in the lenses. The average PD for the adult lies between 54 to 77 mm whereas for kids it is between 43 to 58 mm. It can be easily measured by using a ruler from the center of the right eye to the center of the left eye in millimetres. 

Lens Coating

Apart from the above, you need to fill in the type of lens coating you require that ranges from anti-UV, anti-glare and, anti-blue light and photochromic lenses.  Every coating of the lenses provides their own unique benefits that protect eyes from one or the other harmful rays.

Where most of the eyewear manufacturers charges for the coating of anti-UV and anti-glare. Specscart offers premium anti-glare glasses with anti-UV, and scratch-resistant coatings for free.

How to Understand the prescription for glassesExample 

It may sound little confusing for you, thus, for better understanding, see the following example:

OD  -1.50 SPH +1.00 add 0.75 p.d.

Here,  -1.50 D is the correction of myopia in the right eye (OD). While +1.00 D is for the correction of myopia in the right eyes. As there is no astigmatism correction, there is no power for astigmatism. However, there is the prismatic correction of 0.75 diopters in the eye. 

In another example, 

OS -1.50 -0.50 x 180 +1.00 add 0.75 p.d.

Here -1.50 D is the correction of myopia in the left eye (OS), 0.50 D is the cylinder for correcting the error of astigmatism along with that there is Cylinder power axis at 180 degrees.  Further, there is an addition of +1.00 for correcting hypermetropia or presbyopia. Besides, 0.75 diopters of the prismatic correction in the left eye.


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