Prism lenses: What are they and how do they work?

August 21st, 2017 by EyeXcel

What are prism lenses?

What’s All The Fuss About Prism?

All eye doctors (optometrists and ophthalmologists) use different types of lenses to improve your eye sight and vision. Regardless if you are near-sighted (myopia), far-sighted (hyperopia), or have astigmatism…You may need lenses to bend light differently to sharpen your focus!

However, sometimes the brain’s inability to use both eyes together can lead to a problem with binocular vision.  As a result, this can create trouble focusing (accommodation), turning the eyes inward (convergence), outward (divergence), or double vision (diplopia).


How Do Prism Lenses Work?

Therefore, to assist the brain in turning the eyes in proper directions, eye doctors will prescribe a type of lens known as PRISM to fix the problem.  In addition to compensating for the problem, prism can be used as a therapeutic way to assist the brain in learning how to fix the problem on its own.  This is something brain scientists call neuroplasticity. So what are prisms and how do they work?

In essence, optical lenses bend and focus light, known as refraction. Prism lenses, however, refract light a bit differently.  As a result, this produces a different result on sight and vision. Remember from science class, a prism looks like a pyramid with a base and a pointed top. Light passing through a prism will bend towards the base, while the image of the object viewed with the prism moves toward the peak.

Due to this shift, it appears the object we look at has moved in that direction. Using prisms in different powers and orientation, eye doctors can make a change in the direction of what we see.  As a result, you can experience single vision when there was double vision before.


So Do I Need Prism Lenses?

The path the signal travels to the brain is changed dramatically when prisms are used in the same direction on both eyes, a term called yoked.  Therefore, the brain changes the way it uses this new information.  This can have a dramatic impact on visual processing!

Using prism this way, the eye doctors at EyeXcel treat children with binocular vision issues affecting development or learningIn addition, adults who have suffered a brain injury or stroke can benefit from prism. It also may be helpful for the athlete wanting better vision skills to go to the next level.  Our job is to find the right direction and amount of prism that improves how a person’s brain uses the visual information.

So, if you are experiencing double vision, problems pointing your eyes in the right direction or focusing on the task at hand, make an appointment with the doctors of EyeXcel. Let’s find out if prism just might finally be the solution you’ve been needing!


Dr. Bruce Gilliland
, Optometrist at EyeXcel

28 Responses to “Prism lenses: What are they and how do they work?”

November 09, 2018 at 11:03 pm, James mooney said:

Can you add a cir cular prism to prescription glasses to help with macular degeneration?

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November 13, 2018 at 12:29 pm, EyeXcel said:

James, there are no circular prisms available for macular degeneration. However, we do have other corrective options for patients with macular degeneration which include special magnifiers, digital devices, and binocular telescopes. Please call us at (865) 687-1232 to schedule an exam with our Low Vision expert, Dr. Bruce Gilliland.

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November 16, 2018 at 10:39 am, Diane major said:

My condition is called Spinocerebellar Ataxia (SCA) and it causes me to see double some times. My question is do I have to see double all the time to get glasses with prism or can I have 2 pairs (one just regular glasses and one with the prism) and switch depending on how I see at the time?

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November 19, 2018 at 8:29 am, EyeXcel said:

Ms. Major,

No, you do not need to see double all the time to get glasses with prism. We have done temporary prism lenses for plenty of patients who get intermittent double vision. As you may know, Spinocerebellar Ataxia may also cause difficulties with eye movements and focusing. Please get in touch with us at (865) 687-1232. We would be happy to help! -Dr. Carusone

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November 22, 2018 at 7:10 am, Randy said:

I have been wearing glasses full time for a year now with prism in my left lens only due to eye turn 2 base out. But I have noticed for last little bit I still have an eye pull feeling out wards in the left eye do I need to have the prism increased? Also have noticed my right eye with no prism starting to pull in a bit and starting to get double vision from it so do I need prism for that eye as well? I also have astigmatism and myopic

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November 26, 2018 at 8:47 am, EyeXcel said:

Randy,
Thank you for your questions! The answer depends on the cause of your eye misalignment, nature of the double vision, and amount of misalignment. There are many factors that contribute to the prescription and use of prism lenses. In order to determine what is most appropriate in your case, we would need to gather some more information from you. Call us at your earliest convenience to schedule an exam so we can determine what works best for you. (865) 687-1232
– Dr. Frank Carusone

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November 22, 2018 at 4:19 pm, Kenny Parolini said:

I have had laser surgery several times for macular pucker which, according to my retinal specialists have turn out very well.. I have also had correctional surgery for near sightedness that was only partially successful. I have had laser surgery for cataracts in both eyes. I have been wearing prisms for about 3 years now. I have an ocular neurologist with Will’s Eye who recently took the prism out of my right eye lens which seems to have helped somewhat. It is still difficult to read but possible. I am 77 years old. Driving is a problem do to glare and limited ability to tell which lane cars are in. Is there an answer for this?

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November 26, 2018 at 8:50 am, EyeXcel said:

Mr. Parolini,
Great questions! It sounds like you’ve had quite the history of eye-related issues. It also sounds like you are having multiple issues that all have solutions! Please get in touch with us at your earliest convenience and we’d be happy to set up a time for you to come in to discuss how we can help! (865) 687-1232
– Dr. Frank Carusone

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December 26, 2018 at 3:57 pm, Sarah Chavez said:

I am not near you but am in Baton Rouge, Louisiana. After a brain tumor was removed in my occipital lobe I lost peripheral vision. I have been seen by a local ‘low vision’ specialist but she had only handled two clients with prism glasses. I would like to find a doctor who handles this regularly to ensure I get what I need, if these would help me at all.

How might I find out who to go to local, in Louisiana, or even Houston?

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December 27, 2018 at 8:26 am, EyeXcel said:

Hello Ms. Chavez,

Thanks for getting in touch with us. I am sorry to hear about your loss of peripheral vision. I know how difficult that can be to adapt to. I would encourage you to find a doctor or office who is a member of COVD, the organization of vision therapy and vision rehabilitation. The website used to find a provider in your area is http://locate.covd.org/

– Dr. Frank Carusone

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December 27, 2018 at 10:47 am, Sarah Chavez said:

Thank you so much for the site to find a doctor ‘local’ to me!

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January 12, 2019 at 6:21 pm, Mary Powers said:

I currently have prisms in my reading glasses only. They have helped me see much better for reading. Can prisms be put in my regular progressive lenses?

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January 14, 2019 at 11:14 am, EyeXcel said:

Hello Ms. Powers,

We can absolutely put prism in progressive lenses! Give us a call or stop in to see one of our wonderful opticians! (865) 687-1232

– Dr. Carusone

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January 16, 2019 at 1:10 am, Penny Van said:

Are these glasses used for types of vertigo? My eyes are not focusing right with motion.

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January 16, 2019 at 12:53 pm, EyeXcel said:

Ms. Van,

We use prism lenses frequently for patients with vertigo. Many times the vertigo symptoms can be triggered or worsened by difficulties with eye coordination and alignment. Feel free to get in touch with us to see how we can help! (865) 687-1232

-Dr. Carusone

Dr. Carusone

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January 19, 2019 at 12:11 am, Jean said:

Will prism glasses provide accurate vision for an eye that doesn’t track properly?

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January 22, 2019 at 7:44 am, EyeXcel said:

Jean,

It depends on the cause of the eye that does not track, if the eye is misaligned, and if the eye is able to track to any extent. We would need to get more information to determine if prism is the right solution for you. Please call us to set up an evaluation and we will be happy to assist you in any way we can. (865) 687-1232

-Dr. Carusone

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February 04, 2019 at 9:46 am, Gemma said:

my sister has recently had botox in her eye to relax the muscle turning it. its a week later and she now has the worst double vision she has ever had and the eye is turning out. shes wearing a patch, but is this something a prism could help with?

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February 04, 2019 at 1:14 pm, EyeXcel said:

Hey There Gemma,

I’m sorry to hear that about your sister. Prism can absolutely be used in this sense to correct double vision. Patching the eye is definitely not ideal. Get in touch with us soon to let us know how we can help or to set up an appointment for your sister. (865)687-1232

– Dr. Carusone

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February 04, 2019 at 3:21 pm, Prism Correction | The Hargrave Eye Center said:

[…] Prism correction is mainly used to help people who experience double vision. When someone experiences double vision, they see two images of a single object at the same time. These symptoms can be mild, as some people only see small fragments of a second image making what they are looking at seem fuzzy. This kind of vision impairment is called diplopia and is mostly treated through prism correction. […]

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February 07, 2019 at 8:09 am, Louwrens said:

According to a neurologist,a nerve in my brain and or a spot on my brain-stem,caused my double vision and vertigo.I have glasses with a prism in onthe left side.Will this problem go away by itself and the nerve heal?

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February 07, 2019 at 8:47 am, EyeXcel said:

Thanks for your question!

Double vision can be constant, intermittent (meaning off-and-on), or may resolve over time. It all depends on the cause and whether or not the cause is being treated or rehabilitated. I would encourage you to discuss this with your neurologist and a developmental or behavioral optometrist in your area. If you are in or around Knoxville, give us a call (865) 687-1232.

-Dr. Carusone

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February 07, 2019 at 9:29 pm, larry williard said:

I developed a double vision problem about 3 years ago. It came on pretty sudden. In the morning I see 2 images one on top of the other. After 5-15 minuets it straightens out. I can check the progression by crossing my eyes. I see 2 images the left is higher then the right by abut 6 inches,
as the day wears on it gets worse until late at night the right image is 2x that distance and closer to being under the top image. Its like an arc thought the day. My ophthalmologist thought it was Myasthenia gravis, but did no tests. I went to a Neurologist and he did several tests and said it was a weak eye muscle #4, I believe. Next to an optometrist that specializes in prism lenses. He agreed with the Neurologist and I now have a temporary stick on prism lens. He put it on my non dominant eye. He said I was 2 diopters out. Today is the first day. Tonight I looked at the stars. I never could see just a single star and still cant. Is this normal? The longer I stare at it the worse it gets. Do you think I need more correction or will it get better or is it normal. Sorry for the long post.

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February 11, 2019 at 2:26 pm, EyeXcel said:

Hey Mr. Williard,

I am very sorry about your current double vision problems. A weakened or partially paralyzed cranial nerve 4 (IV) can cause double vision that fluctuates and varies when you are looking at different objects. So to answer your question it is perfectly normal to see double vision only in certain situations. What is often done with temporary stick-on prism is to correct for the amount of eye misalignment that is “most common” or what your eye’s need the majority of the day. Often times vision therapy or neuro-optometric rehab is helpful to assist with maintaining single vision in all positions. I would encourage you to seek out a provider in your area that is associated with COVD (www.COVD.org) or to give us a call if you are in the Knoxville area.

-Dr. Carusone

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February 09, 2019 at 1:28 am, Randall Popkin said:

I had a hemorrhagic stroke 5 yr ago in my midbrain which resulted in a 3rd nerve palsy. The strabismus was much more severe early on than it is now. I’ve been wearing prism lenses since the stroke to correct my diplopia. The problem is that I accommodate to the prisms and after a few months, the diplopia returns, I increase the prism and it works well for another couple of months. Now they can’t be increased any further and the optometrist says I just need to live with the diplopia. Can you think of an alternative?

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February 11, 2019 at 2:28 pm, EyeXcel said:

Mr. Popkin,

There are plenty alternatives to prism lenses to correct double vision. It all depends on the cause, severity, and nature of the double vision. I would encourage you to reach out to a COVD doctor in your area (www.COVD.org) or give us a call if you are in the Knoxville area. (865) 687-1232

-Dr. Carusone

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February 18, 2019 at 11:37 pm, Kiland said:

I have a head tilt that makes me look turn my head right forcing me to use my dominant eye. My vision is fine I just always seem to over compensate for my less dominant eye by tilting my head. Would the prism glasses help correct this or am I better off with eye surgery?

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February 19, 2019 at 9:58 am, EyeXcel said:

Thanks for getting in touch with us!

Prism lenses may be a potential option for your difficulties. It all depends on what is causing the dominant eye to be so dominant and if there are other options available to correct it. Surgery may not be the best solution depending on the problem. I would encourage you to get in touch with our office if you are in the Knoxville area. If not, please check out locate.covd.org to find a COVD doctor in your area.

-Dr. Carusone

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