Double vision is an eye problem where someone begins seeing two different images of a single object. To correct this problem or defect, a prism in eyeglasses can be very helpful.
Using prism lenses helps align two images and enables the person to see only one picture. Further, such correction lenses are very effective in dealing with accompanying symptoms of double vision or diplopia.
Read on as we will try to know what prism correction in eyeglass lenses can do to relieve patients suffering from double vision.
What Is A Prism In Eyeglasses?
Prisms in eyeglasses are triangular-shaped lenses made of glass or plastic. They are very efficient for the light dispersion into a spectrum or shifting the direction in which light will reflect.
Such lenses do not include any focusing strength and cannot correct refractive errors. The best thing they do is trick the eye into assuming that an object is in a different direction to eye alignment.
This element also enables the eyes to recognize images properly, improve binocular vision, and reduce headaches or reading difficulties.
How Does Prism Eyeglasses Work?
Now you know what is a prism in eyeglasses lenses, but how do they function?
Prism eyeglasses turn light in a form that the images seen by your eyes move into the position they need to be. It further resulted in the formation of realigned images. After that, these realigned images are sent to your brain to modify into one picture.
That is how prism eyeglasses are a helpful instrument for rectifying headaches, nausea, dizziness, and several other severe symptoms inflicted by double vision.
Why Do You Need Prism In Eyeglass Lenses?
Doctors recommend prism correction lenses to the patients who experience binocular vision problems and double vision, most typically occurring from:
- Visual problems such as
- Binocular visual dysfunction is an eye problem when the eyes do not align appropriately with each other. Dizziness, nausea, eye pain, and continual headaches are its symptoms.
- Strabismus or crossed eyes is an eye condition in which one eye gets turned in a direction opposite to another eye.
- Myasthenia Travis is an auto-immune disease that prevents nerves from notifying your muscles how to act. Early signs include headaches and droopy eyelids.
- Graves’ disease is a thyroid disease that influences eye muscles. It can result in a vertical diploid where one image is on top of the other image.
- Convergence insufficiency is an eye situation in which the eyes become incapable of working together while looking at close objects. Your eyes may feel strain, headache, rubbing, or closing of one eye.
- Neurological problems such as
- A stroke occurs when a blood vessel in the brain breaks and bleeds. The breakage staves off blood and oxygen from entering the brain’s tissues. Without proper oxygen, tissues and brain cells become weakened and start to die within minutes.
- Diabetes mellitus causes the eye lenses to swell and fluctuates your potential to see. You must bring your blood sugar back to the desired range to rectify this cloudy vision.
- Multiple sclerosis can impact the nerves of your brain or spinal cord. It can also harm the nerves that monitor your eyes.
- Migraine, head injury, and tumors are a few other reasons for double vision.
How Can I Get Prism Correction In Eyeglasses?
Like regular prescription glasses, you need to give an in-depth eye exam to assess your vision. During the exam, your eye doctor may conduct one or more of the following tests to determine if you require a prism lens:
- Hirschberg Test
This test helps your doctor to check strabismus. Under this test, the doctor aims penlight at your eyes. The reflection of light should emerge in the middle of the pupil of both eyes.
If the reflection is off-center in both or either of the eyes, there may be the possibility of strabismus.
- Krimsky Test
Krimsky eye test helps estimate the extent of misalignment. This test is moderately similar to the Hirschberg test but done with a prism.
While staring at the penlight, the doctor will place prisms having different powers in front of the eye.
The doctor will find an accurate prism measurement when the prism gets the reflection in each eye to the middle.
- Cover Tests
There are three categories of cover tests. With the cover-uncover test, the doctor will cover one eye and leave the other eye uncovered. Then he will look for any tendency in the exposed eye.
The prism and alternate cover test put a separate cover over both eyes while a prism gets placed in front of one eye. These tests calculate the variation between the two eyes to know the favorable prism to cure your double vision.
- Maddox Rod Test
Under this test, each eye notices a straight horizontal or vertical line. These images allow the doctor to define what kind of double vision you possess. Prisms are also helpful in completing the distance between the two pictures and assigning the prescription value.
How Does An Eye Prescription For Prism Look?
When you receive a prescription for prism correction in eyeglasses, it will have typically two numbers:
Like regular eyeglasses, diopters measure the proportion of prism correction beginning from 0.5PD. This amount indicates how misaligned your vision is.
As per the double vision, the prism gets placed horizontally, vertically, or diagonally in one or both eyeglass lenses. The base is the heaviest end of the prism and notifies you where the light is changing direction.
It may be on the top edge (Base Up, BU), bottom edge (Base Down, BD), the inner edge (Base In, BI), and external edge (Base Out, BO) of the lens.
How Do Prism Eyeglasses Look?
When the doctor fits a Fresnel prism over your eyeglasses, the prism becomes little visible. This kind of prism is not suitable for long-term use. But it lets you check a prism and see how it operates. Fresnel prisms are also beneficial when the prism prescription is not fixed and may change soon.
But if you need a prism correction for a permanent period, the doctor will make it into a component of the lenses of your glasses.
Having a prism in your eyeglasses will make them look like any other spectacles with prisms. It is possible that one side of the lens is heavier and more visible compared to the other. If this is a problem for you, you can select a thicker frame to protect the portion of the lens.
Do Prism Correction In Eyeglasses Cause Side Effects?
When you start wearing prism in eyeglass lenses, you can face difficulties such as nausea, eye pain, irritation, headache, and double vision.
If you see any of these symptoms, contact your eye doctor, who specified the eyeglasses. You may require the eye frame refit or a new prescription.
Another possible reason behind this problem is the lenses that get out of place and require to get fixed by readjusting them.
How Much Does Prism Correction Cost?
The cost of getting prism in eyeglass lenses varies based on the eye frames you select and if your lenses are designed only to deal with double vision.
Most temporary or Fresnel prism glasses cost about 250 dollars to 500 dollars. Permanent or ground prism eyeglasses cost about 600 to 1500 dollars. There are cases in which prism eyeglasses cost thousands of dollars.
You can talk to your eye doctor to understand the exact cost of prism glasses and discuss methods to decrease out-of-pocket costs.
Are Prism Lenses A Permanent Solution?
Prism lenses will work to alleviate double vision while you are wearing your eyeglasses. But they cannot help you with double vision when you remove glasses. Therefore, prisms are only a temporary remedy.
If you are trying to find a long-term solution for your binocular vision difficulties or double vision, speak with your eye doctor regarding vision therapy.
Vision therapy retrains your eye-brain relationships to enhance your visual skills for clear and single vision with or without eyeglasses.
The Final Word
Prism lenses realign the path of light reaching the eye. These lenses can assist in alleviating symptoms caused by double vision or diploid.
If you are suffering from this issue and have not found help elsewhere, you may consider planning a detailed eye exam that examines your binocular vision. A pair of prism in eyeglasses might be the only thing you want.
We hope you understand what a prism is in eyeglasses and how it helps people with double vision. If you still have questions, ask us in the comment below.