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Prism Glasses: Method to Correct Diplopia or Double Vision?

Prism glasses are specialized eyewear that change how light penetrates the eye to treat or compensate for a variety of vision issues. Incorporating prismatic lenses, which are constructed of a transparent optical substance that refracts (bends) light rays, allows them to function more effectively. 

Prism lenses have two parts to their lenses, including a base and an apex. The base of the lens is thicker than the apex. To meet the unique requirements of the person wearing the glasses, the prism’s orientation within the lens can be changed.

Why Do People See Double?

When a person perceives two images of a single object rather than one, it is known as double vision or diplopia

There are many different causes for this phenomenon, but they are generally related to problems with the brain, ocular muscles, or nerves. Several common reasons for double vision exist, such as these:

  • Strabismus: This condition is characterized by the misalignment or improper movement of the eyes. Double vision may result from the brain receiving two different images, one from each eye, because of strabismus.
  • Muscle damage or weakness: The muscles that regulate eye movement and coordination can become weak or injured as a result of trauma, inflammation, or certain medical conditions. The eyes may be unable to keep proper alignment when these muscles aren’t working properly, which can lead to double vision.
  • Damage to the nerves: A number of things, including head trauma, infections, or specific neurological conditions, can harm the nerves that regulate the eye muscles. Double vision may result from the eye muscles malfunctioning when these neurons are damaged.
  • Brain disorders: Issues with the brain, such as brain tumors, strokes, or other conditions that affect the areas of the brain in charge of interpreting visual information and regulating eye movement, can also result in double vision.
  • Refractive errors: Astigmatism, which happens when the cornea or lens have an irregular form, is one type of refractive error that can occasionally lead to double vision. Incorrect light concentration on the retina as a result of this may subsequently cause blurry or double vision.
  • Cataracts: A cataract is the normal lens of the eye becoming cloudy. As a result, light may scatter as it enters the eye, potentially leading to double or blurred vision. Sometimes, diplopia can occur following cataract surgery.
  • Strain or fatigue: Extended computer use, reading, or other visually demanding activities can occasionally cause extreme eye strain or fatigue that results in double vision.

If you experience double vision, see an eye care specialist or doctor right away because it could be a sign of a serious underlying problem that needs to be treated.

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How Do Prism Glasses Help Double Vision?

By changing the way light enters the eyes and adjusting the perceived picture to account for the alignment or focusing problems causing the double vision, prism lenses can treat this issue. The prism’s strength and orientation can be adjusted within the lens to suit the person wearing the glasses. 

Prism glasses are not a one-size-fits-all treatment for double vision. Other interventions and treatments might be more suitable. An eye doctor can determine the best course of action for your particular situation.

Which Conditions Will Prism Glasses Fix?

Several vision problems can be treated with prism glasses, including these:


Prism glasses can help to realign crossed or misaligned eyes by shifting the picture on the retina, allowing both eyes to function together and reducing double vision.

Diplopia (Double Vision)

Prism glasses can merge two distinct pictures into one by rerouting the light entering the eye, giving the wearer a single, clear image.

Hemianopia (Loss of Vision in Half the Visual Field)

Prism glasses can help individuals with hemianopia see objects that would otherwise be in their blind spot by enlarging their field of vision.

Convergence Insufficiency

Prism glasses can help with convergence insufficiency, or difficulty focusing on close objects, by changing the angle at which light enters the eye. This makes it simpler to concentrate on close objects.

General Eye Strain & Fatigue

In addition to treating other vision issues, prism glasses can also be used to alleviate the eye strain and fatigue brought on by extended computer use or other visually demanding activities.

When Are Prism Lenses Prescribed?

Prism lenses are prescribed when standard eyeglasses or contact lenses alone cannot rectify a patient’s vision issues. The need for prism lenses is determined by an eye care professional, such as an optometrist or ophthalmologist, based on a comprehensive eye exam and the individual’s specific vision issues. 

Prism lenses may not be appropriate for everyone, and their efficacy depends on the underlying cause of the vision problem. In some cases, alternative treatments or interventions may be preferable.

What Tests Are Performed to Determine if You Need Prism Glasses?

An optometrist or ophthalmologist will conduct a comprehensive eye examination to determine if you require prism glasses. This examination typically consists of multiple exams to evaluate your vision and eye alignment. These exams may be conducted:

Visual Acuity Test

This test assesses the clarity of your vision at various distances, typically with the aid of a Snellen chart or other standardized eye charts.

Cover Test

This test evaluates how well your pupils coordinate with one another. The eye doctor will instruct you to focus on a target while covering and uncovering each eye individually. This aids in the identification of any misalignment or abnormal eye movement that may be causing double vision or other issues.

Extraocular Muscle Function Test

The extraocular muscle function test evaluates the functionality of the muscles responsible for eye movement. The eye care professional will ask you to keep your head still while following a moving target with your eyes. This serves to identify any muscle weaknesses or imbalances that may be affecting the alignment of your eyes.

Prism Cover Test

This test is a variation of the cover test in which prisms of differing intensities are positioned in front of one eye while the other is covered. The eye care professional will then observe how your eyes react to the prisms in order to determine the appropriate prism power required to correct your vision impairment.

Refraction Test

This test helps to determine your eyeglass prescription, including any prism correction that may be required. 

The eye care professional will place various lenses in front of your eyes while you view an eye chart. They’ll then ask you to select the lens that provides the clearest vision. This procedure determines the optimal lens prescription for your requirements.

General Eye Exam

Examining the overall health of your eyes, the doctor will check for any signs of injury, disease, or other conditions that could be affecting your vision.

What Do Prism Glasses Look Like?

Prism glasses look the same as normal reading glasses, and the thickness of the lenses is not visually different. 

Are There Potential Side Effects?

Prism glasses may initially cause side effects as you adjust to wearing them. Potential side effects include the following:

  • Headaches
  • Nausea
  • Double vision
  • Pain in the eyes


  1. Peripheral Prism Glasses: Effects of Moving and Stationary Backgrounds. (April 2015). Optometry and Vision Science.

  2. Prism Glasses. (August 2022). StatPearls.

  3. What Is Prism Correction in Eyeglasses? (March 2021). American Academic of Ophthalmology.

  4. Diplopia. (February 2023). StatPearls.

  5. Causes and Outcomes of Patients Presenting with Diplopia: A Hospital-Based Study. (March 2021). Neuro-Ophthalmology.

  6. Understanding, Detecting, and Managing Strabismus. (March 2010). Community Eye Health Journal.

  7. Diplopia as the Complication of Cataract Surgery. (February 2016). Journal of Ophthalmology.

  8. Prisms in the Treatment of Diplopia With Strabismus of Various Etiologies. (February 2022). Indian Journal of Ophthalmology.

  9. Clinical and Laboratory Evaluation of Peripheral Prism Glasses for Hemianopia. (May 2009). Optometry and Vision Science.

  10. Functional Anatomy of Extraocular Muscles During Human Vergence Compensation of Horizontal Heterophoria. (July 2019). Journal of Neuropharmacology.

  11. Effects of Prism Eyeglasses on Objective and Subjective Fixation Disparity. (October 2015). PLOS ONE.

Last Updated May 24, 2023

Note: This page should not serve as a substitute for professional medical advice from a doctor or specialist. Please review our about page for more information.

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