How do you correct for Prism when buying glasses online?

An essential part of achieving a clear vision is ensuring that both eyes work together to properly converge individual images into one final image. This is the final product of what you “see”. But there are a lot of things that can go wrong. One thing maybe a double vision. Luckily, prism correction in prescription glasses can correct for the convergence error which causes double vision. 

What Causes Double Vision?

One of the most common causes of double vision is called strabismus. This is when one or more of the six muscles connected to the eye does not function correctly. If one of these muscles does not pull the eye in the correct way, this will prevent the eye from converging images properly. If this is happening, you may experience eye fatigue and strain, limited depth perception, and trouble with focus.

When your brain is not able to fuse the two images from each eye together to form one final image, you will experience blurriness and double vision. That’s not good! Luckily, your eye doctor can write Prism correction into your prescription to fix this problem. Let’s dive into what Prism means. 

What Does Prism Mean, Exactly? 

A prism is a 3D triangle. Picture a mini Egyptian pyramid and you’re on the right track. At their core, all prescription lenses are made of prisms. The main function of a prism is to bend light, and that is exactly what prescription glasses do. 

If you are experiencing strabismus, you will need extra prisms in your lenses placed in specific locations to redirect light into your eyes. It’s as simple as that! Extra 3D triangles in your lenses.

How does Prism correction work?

It may sound complicated, but prism correction just involves redirecting a bit of light into your eye so that your brain can successfully converge the two images. The prisms are placed in the lenses in specific locations and at a specific power to correct for the weaknesses of the eye muscles. Your eye doctor will write the exact amount of correction you need on your prescription. 

What does Prism look like on your Prescription?

If you have a typed prescription, you will see your prism correction in a specific box on your Rx. If it is a hand-written prescription, you may see a small triangle. That’s your prism correction! Your doctor will write the prism information for one eye or both and be in the form of a positive power (ex. +2.00) with a specified direction (+2.00 BD means 2 diopters of prism base down). Prisms will be either base down (BD), up (BU), in (BI), or out (BO). You may even need two prism corrections for each eye.

How can you order Prism correction glasses online from Payne Glasses

You’ve found the prism correction on your Rx, and now it’s time to order your glasses from Payne Glasses. Here is where you will find the Prism Correction portion of the prescription form:

Select the Prism Correction box, and you will be able to enter your prism values.

How does Prism relate to Pupillary Distance?

An unfortunate consequence of having an incorrect PD (pupillary distance) when ordering prescription glasses is that this can cause unintended prism in the lenses. This will cause eye strain and blurry vision. That’s why it is so important to have an accurate PD measurement. Additionally, the stronger your prescription, the greater the chances you’ll have induced prism in your lenses when the PD is off. Be sure to double and triple check your PD!