Prism in Glasses: What Is It and How Does It Impact Vision?

1-12 prism diopters.

Prism correction is an optical element added to your glasses to reduce or eliminate double vision, also known as diplopia.

In the video below, Sheena Taff discusses what you need to know before getting prism put in your glasses.

If you don’t like the video or want more information, continue reading.

Do you need prism in your glasses?

When experiencing double vision with both eyes open, the images entering your eyes are falling in two different places on your retinas. Unfortunately, this causes double vision. Prism in glasses helps re-align the images at the same point in the back of both eyes. Doing so allows you to fuse both images together to create one, single image.

Fortunately for you, your optometrist or ophthalmologist can prescribe you prism to aid in managing your double vision. Depending on your need, prism is measured and prescribed in diopters, ranging anywhere from 0.5 diopters up all the way up to the extreme 40 diopters (although I have yet to see it prescribed that high)!

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Prism in glasses can be prescribed as low as 0.5 diopters and as high as 40 diopters.

Prism base can be set up, down, in or out, and works to shifts the image location to trick your brain into thinking the images are in the same place, thus creating one clear image. Also, prism can be placed all in one lens or split between two lenses. Both achieve the same result and allow your eyes to work together in unison.

Causes of double vision

Double vision can be caused by a muscle imbalance in your extraocular muscles, such as an eye turn (i.e strabismus) or a disproportion in the prescription required in each eye.

Other causes of double vision that can benefit from prism include a stroke or concussion-related brain injury.

Fresnel prism example.
This is what fresnel prism looks like before being put on your glasses.

Fresnel prism

Lastly, your eye doctor may suggest a trial with fresnel prism before prescribing it for your glasses. Fresnel prism is a press on vinyl sticker that easily adheres to an existing pair of glasses. Once applied, it can be removed without damage to your current glasses.

Fresnel prism often gives instant relief of double vision and is an opportunity to try the benefits of prism without risk or major cost.

Think you could benefit from prism in your glasses? Visit your local eye care professional today!


  1. My coworker had a patient that was prescribed 4 down OS. When we applied the Fresnel, it was great. We made the glasses and it was not as sharp. We tried to balance it OU. It still was not as sharp. Why would the vision be clearer with the Fresnel?