What are Prism Glasses? Everything you need to know!

What are prisms? Why are they used in glasses? How do prisms effect how you see?

Maybe you just were told you need prism in your glasses, or maybe you have had them for years and just never were quite sure what they meant.

Good news. This article is all about prism, what exactly that they do and why some people need them.

What are prism glasses?

Prism glasses are a change made to your glasses to improve your eyesight by maximizing eye coordination and reducing the negative effects of stressful vision problems such as double vision, visual fatigue, and headaches.

Unlike glasses that people wear to correct eyesight based on vision, prism glasses help keep both eyes looking in the same direction. Prism glasses are much more than an ordinary pair of glasses. When they help your eyes work together, which is something that they were designed to do, all the while correcting any vision defects that you may have and eliminating eye strain and chronic headaches.

Due to your eyes functioning better. Prism glasses can help improve concentration, and productivity. They can even help children who struggle in school with focusing problems.  

What exactly does prism mean?

A prism is a triangular shaped lens that bends light in different directions. It works almost like a mirror, redirecting light to focus on a particular area. Prisms are used for more than just glasses. They are also used in binoculars, cameras and even telescopes.

The legendary scientist Isaac Newton used prisms to prove that light is made up of different colors and the famous “Dark side of the moon album” by Pink Floyd shows light entering a prism and being bent into different colors.

How does in prism eyeglasses work?

Prism eyeglasses are most often used to treat a misalignment between your eyes (called "strabismus") or for the treatment of double vision. Prism glasses can also be used as optical aids, in the treatment of other conditions such as binocular vision dysfunction (BVD), nerve palsy and more.

As strange as they may look on their own, prism glasses were designed with a specific purpose in mind and are barely noticeable when in glasses. Understanding how prisms work can help you better understand why people would choose to wear prism eyewear.

When your eyes are not aligned, you may often find that both eyes don't agree on where to look. Prism glasses allow your eyes work together as if they were in alignment. This is because the prism lenses in your glasses are designed to make what you focus on appear in the center of your vision, no matter where you're looking naturally.

Your eye doctor does this by setting a measuring how much the alignment of your eyes are off by when compared to another when focused at an object by getting this measurement they can apply it to the prism and have both sides look equally at things.

When are prism lenses prescribed?

When an eye doctor tells you that you need glasses, he doesn't usually prescribe prism glasses right away. Sometimes he tries different things to see if what you need is just frames or just exercises to improve your vision.

Often some people don't always respond to prism and their eyes just adjust to the prism and remain unaligned.

So often, when prism is prescribed it is either the best option possible or the last option possible. With that said it is important to know that if you are prescribed prism there's a pretty good chance your doctors believe you will really need the need it to help you see clearly.

Prism in glasses for double vision (Diplopia).

Prism glasses can be specially designed to help people who have double vision also known as diplopia. Double vision means you see two things at the same time, and it is hard to do simple things like drive a car or read. Regular glasses can treat how clear you see but they do not provide much help for double vision.

Thankfully, often prism glasses can successfully treat double vision and help those with brain injuries or injuries to the eye muscles and nerves. Which is good because double vision can come with serious symptoms such as nausea, headaches and even having eyes that look like they are going off in different directions.

NOTE: You should talk to your doctor about your double vision if….

  • It’s new and you recently noticed it.
  • It’s caused by an eye not being properly aligned.
  • It is caused by some unknown reason.

Prism in glasses for strabismus & lazy eye.

One of the most common causes of double vision is strabismus. Strabismus is when one or more of the six muscles connected to the eye does not work correctly. This causes one of the eyes to be out of place.  Additionally, these muscles are in control for focusing and moving the eye. If they do not work properly, your eyes will have trouble seeing.  

It is important to note that prism glasses do not treat strabismus, instead they help with the symptoms of strabismus such as double vision, eyestrain, and the appearance an out of place eye.

Lazy eye (amblyopia) is often confused with strabismus to mean that an eye is out of place. A lazy eye occurs when one eye cannot see as well as the other due to irregular vision development in the early years of life.

It is called lazy eye because it appears as though the affected eye is “looking out of the corner of its eye “however this eye may still work and move with reasonable clarity.  Lazy eye cannot be treated with regular glasses, prism glasses, or contacts.

Binocular vision dysfunction prism glasses.

Binocular vision dysfunction (BVD) occurs when the eyes are not aligned but unlike strabismus it is not as obvious and may not lead to double vision. Normally, the eyes work together to create one image that is projected onto the retina which ultimately leads to depth perception, or an ability to distinguish between objects that are closer or further away from you. With BVD, the images are misaligned causing poor depth perception and can lead to eye strain headaches, nausea, dizziness, and other symptoms.

People with BVD often benefit from getting prism in their glasses.


Related Article: Blurry Vision & Headaches: What Does it Mean?


Other reasons to be prescribed prism.

Prism may also be prescribed for other conditions. Here are a few other examples below.

Vision problems caused by:

  • Convergence insufficiency
  • Myasthenia gravis
  • Graves’ disease

Neurological problems caused by:

  • Stroke
  • Migraine
  • Head injury
  • Tumor
  • Diabetes mellitus
  • Multiple sclerosis


Do I need prism glasses?

The best way to know if you need to be prescribed prism is by visiting your eye doctor and getting a comprehensive eye exam. Your doctor will run several tests to determine if you need prism.

If you feel that your eyes are not functioning properly, it’s important that you see your eye doctor immediately. They will determine if you need prism glasses or any other treatment.

If you’re unsure whether prism eyeglasses will help your vision, schedule a consultation with an Optometrist. Together, you can discuss your symptoms and determine what treatment is best. 


What does a prescription for prism look like?

A prism distinction is added to your eyeglass prescription, and you can usually find it under the section that says “Prism” this is only one half of the prism prescription, however. There is another section that says “Base” that is apart of your prism prescription. These two parts describe your prism prescription. The “Prism” describes the intensity of prism you need (how much you need the light to bend) and the base describes what direction you need the light to bend (seen as BO, BI, BD, BU).


Difficulty adjusting to prism glasses.

If you find your prism glasses aren’t working as well as they should, it’s possible that your eyes need more time to adapt to the new prescription. This is not uncommon for people who are new to glasses.

You may also need to ask for an adjustment to your glasses after you first get them. Adjustments can sometimes cause difficulty when trying to adapt to a new pair of glasses, especially ones with prism in them.

 If you have difficulty adjusting to your new prism glasses, it’s important to contact your optician. He or she will be able to help and will be able to determine whether you still need time for adaptation.

Are prism lenses a long-term solution?

For patients with strabismus and a small amount of eye misalignment, wearing prisms may be a good long-term solution.

Unfortunately, for people with larger alignment problems, prisms may only serve to improve alignment temporarily and strabismus surgery may be the preferred way to treat the eyes.

Do prism glasses cause any side effects?

Common side-effects of prism eyeglasses include:

  • Headaches
  • Misaligned eyes
  • Nausea
  • Double vision

How Do I Get Prism Put in My Glasses?

Prism gets put in your glasses while your prescription is added to your glasses often when you receive your pair of glasses the prism is automatically in the lenses. However, sometimes you can use a press on prism that sticks onto the front of your glasses and allows you to have a prismatic prescription.


When visual needs are appropriate prism can be an excellent option to help with several eye conditions. If you experience any of the conditions in this article, then it may be time to start looking into prism glasses.

If you are looking for the perfect frames for your new lenses, you may be interested in the most stylish and comfortable glasses on the market.

Just remember, it starts with a visit to your eye doctor for a comprehensive eye exam.

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