Prism Glasses

What Are Prism Glasses?

Those who experience double vision don’t have normal binocular vision. Those with normal vision have similarly shaped eyes, which means the light entering the eye will hit the same place on the retina, reflecting a unified image. For those with double vision, the eyes may be differently shaped, making the light fall differently on each eye's retina. When the light bends differently in each eye, it creates an image that is disjointed, resulting in double vision.

You might remember from childhood that a prism is a transparent object with a multifaceted surface. Prism lenses are similar. Designed to capture and bend the light, they can align the light that enters the eye, virtually eliminating the double image those with double vision have to interpret.

Who Needs Glasses With Prism Correction?

It’s best to check with your eye care professional before ordering prism glasses to ensure they will help and get the right prescription to align your eyes. As noted above, there can be many causes for double vision. An ophthalmologist will be able to diagnose and measure the misalignment, discuss options with you, and help you decide whether prism glasses are the best option for you.

Beyond double vision, prism glasses will also be useful for those who suffer from:

• Eyestrain
• Frequent headaches
• Tired eyes and vision fatigue
• Strabismus, an eye alignment disorder
• Myasthenia Gravis, weak eye muscles
• Grave’s disease, a thyroid condition that weakens the eye muscles and tissues
• Those who are recovering from head injuries or stroke
• Some who suffer from migraines
• Some patients with certain tumors that may cause eye misalignment
• Multiple sclerosis, which can cause nerve-related problems in the eye
• Diabetes mellitus, a common cause of eye nerve damage

Even if you have an existing prescription, you can get a prism correction added to your glasses prescription.

What Does Prism Look Like On Your Prescription?

You will notice a separate set of numbers on your prescription for those who need a prism correction. These numbers indicate the vertical and horizontal angle needed to correct the individual’s specific double vision source.

If you are ordering your prescription online, you’ll need to be able to enter your prism prescription during the ordering process. In a typed prescription, you’ll see a prism correction field that will be marked. Most written prescriptions will have a small triangle to indicate your need for prism lenses.

A prism correction will be for one lens or both. You’ll see a positive power, such as +2.00, indicating the strength of the prescription. You’ll also see a direction after that number. For example, you might see +2.00BD. The direction indicated whether the prescription adjustment direction is base down (BD), base up (BU), base in (BI), or base out (BO). It is entirely possible to have multiple corrections per eye.

Prism lenses are a tremendous help for double vision. While there are multiple reasons someone may suffer from double vision, prism glasses are a few simple corrections that are safe, inexpensive, and don't require surgery. It’s worth asking your physician about getting a prescription and ordering your new prism lenses for better vision.