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

59 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?

Reply

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.

Reply

February 21, 2019 at 1:06 pm, Martin said:

> hello.i recently failed my hgv peripheral vision test.could a prism help as can only get to @ 70% on right eye.left eye ok ?

Reply

February 27, 2019 at 11:38 am, EyeXcel said:

Mr. Robinson,

I’m not sure I totally understand your question. Are you saying that you failed the peripheral vision test associated with your HGV truck driving examination and are asking if prism could help get you to the point of passing the test? Prism unfortunately does not improve your functional peripheral vision. It can only make you utilize your remaining vision more effectively (i.e. increasing your awareness of certain areas of your vision that are difficult. I would encourage you to get in touch with our office for an exam (865-687-1232) or to find a COVD doctor near you. http://locate.covd.org/

-Dr. Carusone

Reply

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?

Reply

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

Reply

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

Reply

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

Reply

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?

Reply

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

Reply

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?

Reply

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

Reply

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

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

Reply

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?

Reply

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

Reply

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.

Reply

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

Reply

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

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

Reply

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

Reply

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?

Reply

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

Reply

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. […]

Reply

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?

Reply

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

Reply

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.

Reply

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

Reply

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?

Reply

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

Reply

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?

Reply

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

Reply

February 20, 2019 at 6:06 pm, David Carr said:

Have you ever heard of someone with triple vision?

Reply

February 27, 2019 at 11:48 am, EyeXcel said:

Mr. Carr,

Yes I have heard of triple vision but it is usually what most patients describe true double vision as or secondary to extreme blur or astigmatism.

-Dr. Carusone

Reply

February 27, 2019 at 9:48 am, Mya Lockhart said:

I had surgery to fix my “lazy eye” when i was two years old. After the surgery i went through years of patching and my doctor thought that my eyes looked fine. Im eighteen now and ive been experiencing motion sickness and light sensitivity for many years, however, its been quite severe recently. My eyes constantly feel strained and there isnt a day that goes by where i dont have a headache. Would prism glasses help with this or is this a sign that im going to need another eye surgery?

Reply

February 27, 2019 at 11:32 am, EyeXcel said:

Ms. Lockhart,

We have many patients who have similar stories to yours (surgery/patching/drops when younger but still have symptoms). Prism may or may not be the solution to your problems. It all depends on the nature of the eye turn, coordination of eye movement and prescription needed. I would encourage you to come see us if you can (865-687-1232) or to find a COVD doctor in your area. http://locate.covd.org/

-Dr. Carusone

Reply

February 27, 2019 at 1:36 pm, larry williard said:

3 years ago I started getting double vision one image above the other. The longer Im up the worse it gets. Turns out my eyes can put them together for about 12 hours when the right one starts to drift down causing the double vision, causing it to look like one car on top of another. My ophthalmologist thought it was Myasthenia Gravis but I had no other symptoms. A neurologist said it was a week 4th eye muscle. Finally I went to an optometrist who said he could fix it with 1 prism lens. He also said he gets up to 5 patients a week and its common. So he ordered a plastic stick on for one eye and so far its perfect. I have a followup in a week to get a new prescription for 1 lens.

Reply

February 27, 2019 at 8:11 pm, Sanan said:

I have Exotropia strabismus for one eye, does this Prism lenses will help me?

Reply

February 28, 2019 at 7:54 am, EyeXcel said:

Sanan,

Prism is often one of our first choices of treatment for exotropia. Vision therapy may also be of great benefit. Please contact us to set up an appointment (865-687-1232) or locate a COVD doctor near you. locate.covd.org

-Dr. Carusone

Reply

March 02, 2019 at 12:26 pm, Daily F Kizer said:

I have double vision in my left eye only. This only developed permanently in the last month. If I do a crude pinhole test by punching a hole in thin cardboard and looking at an eye chart through the pinhole the previously “blurrred” image is clear of the double image (with the right eye covered). The leaders on my television set also clear up when viewed through the pinhole. My retina doctor ( I have stable macular degeneration in my right eye.) has recommended prism glasses. That doesn’t make sense to me to wear prism glasses because the problem is only in one eye and it clears up with the pinhole, indicating a refraction problem to me. I have a BS in physics. So, has my limited knowledge of the biology of eye and the little I know about optics caused me to make a big mistake by second-guessing my doctor? He has only done crude tests such as having me look up and down and compare resolution of the same object with different eyes.

Reply

March 07, 2019 at 5:18 pm, EyeXcel said:

Mr. Kizer,

The pinhole effect is a phenomenon that can sometimes help us identify refractive error or potential improvement with a refractive correction. However it does not always mean that you vision is correctable. Macular degeneration is a progressive disease of the retina so I would encourage you to find an eye care provider for routine care and monitoring. If you’re in our area give us a call (865-687-1232) or find a local provider in your area. Prism does not seem to be the solution to your problem based on the information you’ve provided.

– Dr. Carusone

Reply

March 04, 2019 at 9:00 am, Cynthia Heck said:

My stepmother suffered a vertebral stroke in Dec.It affected her occipital and parietal lobes.She has some letter recognition and numbers. she is currently working with a speech therapist. Her peripheral vision is gone and she has to using tracking of her head to focus on letters. She has tunnel vision and is seeing double. She has had cataract surgery in the past. Are prism glasses something that could help her see more clearly?

Reply

March 07, 2019 at 5:14 pm, EyeXcel said:

Ms. Heck,

I am very sorry to hear about your stepmother’s recent stroke. I know how difficult of a process it can be to recover. It sounds like with her recent difficulties with peripheral vision and tracking she may benefit from vision rehabilitation more than prism lenses. Prism may be able to help her with her double vision but it is dependent on the nature of the double vision and severity. Please get in touch with us to schedule an evaluation with myself or Dr. Gilliland and we would be happy to help. If you’re not in the East Tennessee region, locate a COVD doctor using this link http://locate.covd.org/

-Dr. Carusone

Reply

March 22, 2019 at 8:40 am, RAGHAV KWATRA said:

Hi DEAR SIR
I HAD SQUINT SINCE BIRTH
THERE WAS A SQUINT SURGERY WAS PERFORMED WHEN I WAS ONLY 7 AFTER surgery the squint was not proper gone and it created double vision vision i.e crossed double vision as a result my right eye is squint free my left eye has squint the difference between eye is 25% and when ever I try to focus from my right eye the second images goes away but still I can see 10% of second image and I do not concentrate it always two now I m 22 and I want my squint surgery but doctor told that you should wear prism first if it works she will perform surgery
So I want to ask if prism really works or not i.e will I see a single image from prism or not

Reply

April 17, 2019 at 9:27 am, EyeXcel said:

Thank you for your question. Prism is very helpful in the case of double vision caused by “squint” or eye misalignment. I would encourage you to set up an appointment with our office at (865) 687-1232 or to locate a COVD doctor in your area at locate.covd.org

-Dr. Carusone

Reply

March 29, 2019 at 5:37 pm, Charles said:

I had a crainiotomy 7 weeks ago to remove a benign tumor . I have severe double vision now . The tumor was pressing on my 6th cranial nerve . Do you think my vision will return to normal ? The neurologist said it would go away but could take months. Will prism glasses help with healing ?

Reply

April 17, 2019 at 9:25 am, EyeXcel said:

Charles,

Thank you for your question. I am sorry to hear about your 6th cranial nerve issue. It sounds like prism can be helpful in your case to eliminate the double vision. As far as returning to normal, that depends on the extent of damage done to the optic nerve. Vision rehabilitation can assist in improving your eye coordination and movements. I would encourage you to get in touch with our office at (865) 687-1232 or to locate a COVD doctor in your area at locate.covd.org

-Dr. Carusone

Reply

April 17, 2019 at 8:37 pm, Charles Burleson said:

I now have prism glasses to correct my double vision . They do stop the double vision but they make me dizzy and my eye sight is not plain. Does it sound like a problem with my prescription or is this the best I can hope for ?

Reply

April 22, 2019 at 1:03 pm, EyeXcel said:

Mr. Burleson,

I am sorry to hear about your issues with prism lenses. It sounds like it may be a prescription and/or fit issue. I would encourage you to return them to the office you got them from and to discuss that with the doctor who prescribed them. If that is our office, give us a call at (865) 687-1232.

-Dr. Carusone

Reply

April 22, 2019 at 5:57 pm, Charles Burleson said:

I took my prism glasses back to my doctor and he said they were about the strongest prism prescription . Also said prescription was correct and he could not any make them better as far as blurriness. I had 20/25 vision before double vision. Said I would just have to wait until double vision goes away to see plain.

April 23, 2019 at 9:09 am, EyeXcel said:

I would encourage you to seek a second opinion. It sounds to me like your issue has not been addressed properly. If you’re in the East Tennessee area give us a call (865-687-1232) or find a COVD doctor at locate.covd.org

-Dr. Carusone

April 01, 2019 at 9:47 pm, Dan said:

I had epilepsy brain surgery in January of 2018. They removed a portion of my right temporal lobe. As I understand it they damaged the Meyers loop and the peripheral vision in my upper right quadrant is gone. My neurologist didn’t give me much hope that it would return but he doesn’t impress me. Will prism lenses help with this deficit?
Thanks

Reply

April 17, 2019 at 9:21 am, EyeXcel said:

Dan,

Thanks for your questions. I am sorry to hear about your epilepsy and required brain surgery. We are definitely here to help. Often times peripheral vision loss can be assisted with prism lenses. Please get in touch with us at (865) 687-1232 to set up an evaluation or contact a COVD doctor in your area, locate.covd.org

-Dr. Carusone

Reply

April 08, 2019 at 8:05 am, ichayan said:

I have a prescription in which it says Prism “In”. But the online optician is asking if the direction is left or right? Could you please help?

Reply

April 17, 2019 at 9:19 am, EyeXcel said:

This depends on which eye it is placed over. If it is the right eye, base IN prism would be to the left. If it is the left eye, base IN prism would be to the right. Think of it as which direction the prism is in relation to the face as you’re looking through the lens. Hope this answers your question.

-Dr. Carusone

Reply

April 15, 2019 at 10:24 am, James Damico said:

I had a prism put in my glasses (a 2 up in left and a 2 down in right) when I was 17 years old (1976). From 1978 until 1989 my prism was increased to a max prism in both lenses. I had eye muscle surgery in 1989 because of double vision correcting my eyes to no longer require any prisms. In 2017I required a 1 prism in each lens and recently a 2 prism in each lens. Do prisms cause eye muscle weakness? I’m afraid that history is repeating itself.

Reply

April 17, 2019 at 9:18 am, EyeXcel said:

James,

Thank you for your question. Prisms do not cause eye muscle weakness. There is however often times an “adaptation effect” that the brain and eyes can become “adapted” to the amount of prism required and require a change in amount. Ultimately it depends on the cause of the eye misalignment and how well your brain is able to compensate for the amount of misalignment. I hope this helps. If you have more questions feel free to set up an appointment with our office at (865) 687-1232.

-Dr. Carusone

Reply

April 20, 2019 at 2:01 pm, Alice said:

I had a major stroke at 53yo. I already had presbyopia. After the stroke , I have left homomynous hemianopsia, My ophtho told me there was no therapy available and no hope of improvement. we discussed prism glasses but he discouraged me. I am now 65 and13 years post stroke. I am very leary of driving. is it too late for me to seek any kind of rehab or correction?

Reply

April 22, 2019 at 1:50 pm, EyeXcel said:

Ms. Alice,

It is absolutely not too late to seek out vision rehab or correction for your hemianopsia! I would encourage you to give our office a call to schedule an appointment (865-687-1232) or find a COVD doctor in your area at locate.covd.org
Best of luck!

-Dr. Carusone

Reply

April 20, 2019 at 9:53 pm, Marcia Johnson said:

O have myasthenia gravis which affects the voluntary muscles in my body. I had double vision because of it. My eye doctor put prisms in my glasses and it has worked out great for me! I can now drive again!

Reply

April 22, 2019 at 1:52 pm, EyeXcel said:

Ms. Johnson,

It is so great to hear another success story from neuro-optometry rehab! So happy to hear you are back to driving!

-Dr. Carusone

Reply

Leave a Reply

Your email address will not be published. Required fields are marked *