Millions of people wear eyeglasses, but few give much thought to how those glasses work. They know that the frames hold the lenses in place, but beyond that, they’re fairly clueless. Those who see their prescription see a lot of small numbers, symbols and letters and don’t even think about asking the doctor what any of those things mean. Some of those symbols found in the prescription relate to the prisms found in the lenses.
Designer eyeglasses and cheaper glasses alike use prisms as a way of making regular glasses better for the wearer. The purpose of prisms is to twist light into different colors, which is also known as bending the light. Pure white light is actually made of different colors that aren’t visible to the naked eye. When an individual has problems with their eyes, they can sometimes see all those colors. The individual sees these colors right at the corner of their eye or along the edges of a scene, which gives it a slightly blurry look.
Prisms have a slightly conical look to them. The best way to see this is by looking at a contact lens lying flat on a table or in the hand. The user will notice that the contact isn’t exactly flat, but has a slightly rounded edge to the top. When light goes into this area, it bends and returns back out of the lens in the opposite direction. When this happens, it bends the light again and fixes the colors the person sees. This is also true in prescription glasses.
An individual who has vision problems feels something known as eye strain, which is caused by the position of the muscles in the eyes. When they have difficulties seeing, they automatically adjust their eyes to make it easier to see. A good example is the individual who squints because they want to see things that are far away. This strains the eye muscles and causes them to slowly break down over time.
Prisms in the lenses of the glasses or in the contacts correct this strain. The prisms in those lenses cause the eyes to focus in the correct way and prevent the person from straining the muscles of the eye. They no longer have to squint or physically adjust their eyes to see things properly because the prisms do that for them. The amount or size of the prisms is generally discovered during the eye exam when the doctor begins measuring the eye.
Those who wear glasses or contact lenses often are unsure of prisms and unsure how they work. They’re actually found in all forms of prescription eyewear because all those in need of corrective lenses need prisms. The prisms correct the way they see and make it easier for the light to enter the eye. The prisms also make it easier for the light to exit the eye, but only after bending the light and changing the color that the person sees. It’s easily one of the most important parts of the prescription.