Prism glasses are a special type of eyeglasses used to correct double vision for people with diplopia. When someone simultaneously sees separate images of one object, prism lenses correct the double vision by aligning the images. Prism eyeglasses refract light before it reaches the eye in order to redirect it to the right spot on the retina of each eye so that the brain is able to piece together one image. To buy prism glasses for the double vision you will need to take an eye exam to determine the cause and receive a prism glasses prescription. Prism glasses cost varies with insurance but can range from $250 to $500.