Prism Lenses | Treatment Of Double Vision And Visual Field Loss

Prism Lenses

What is Prism?

Prism is a type of lens that is shaped in a way to bend the light that is coming into the eye. This means that we can "move" images seen by the eyes/brain to a place that is more comfortable for the eyes to see - allowing for single, clear, and comfortable vision.

Types of Prism

Compensating Prism

Most often prism is used to help with eye alignment/double vision. When the two eyes are not pointed in the same direction then the brain receives two different images and interprets the world as being seen in double. With compensating prism, we can bend the light traveling into each eye in a way that moves the images closer to each other to fix double vision.

Yoked Prism

Yoked prism is used to move the images of both eyes in the same direction. Yoked prism is helpful for patients who have gaze palsies where both eyes can't look up or down - often due to conditions like brainstem stroke, restrictive strabismus (e.g., thyroid eye disease), nystagmus, abnormal egocentric localization, as well as cervical disorders of the neck that may cause patients to be unable to look in a certain gaze due to physical limitations of the neck's range of motion.

Visual Field Expanding Prism

There are many types of "field expansion" prisms including Peli Prisms, Gottlieb prisms, and yoked prism, which can be used for patients who have neurologic visual field loss like homonymous hemianopsia. While this prism does not give patients their full peripheral visual field back, this prism can expand the field by 3-25 degrees which can help patients with things like reading, walking/ambulating in public​

Fresnel Prism

Fresnel is a type of temporary prism sticker that can be used for patients who are unsure if prism will work for them and want to try it on their glasses first before buying it. It can also be used for patients who only need prism for a certain gaze when they only get double vision when looking in a particular direction like left or down.

Prescribing prism is an art.

The eyes are dynamic and can fluctuate throughout the day, so sometimes it can take a few attempts to get the prism correct. If Dr. Theis is concerned that your double vision fluctuates or the prism prescription may need a trial period, she will prescribe a temporary Fresnel prism to figure out what works for you outside the exam room.