Sometimes a person may have problems with loss of peripheral (side) vision. One common reason may be if that person has suffered a stroke. It is not unusual for vision to be affected in both eyes on either the right or left side, depending on which side of the brain the stroke occurred.
Prism visual field expansion involves adding prisms to a person’s glasses on the side of their vision loss. This shifts the field of vision within the “blind spot”, so that objects that would not normally be able to be seen will become visible. Prism visual field expansion does not shift the images out of the blind spot into the central field of vision. The prisms should not interfere with the central vision at all. Prisms are located on only one lens of the glasses, above and below the eye. To use them, a technique called “spotting” is employed- meaning a quick look into the prism will show the object that is in the blind spot. The main purpose of prism visual field expansion is to increase mobility in someone whose peripheral vision is affected. In some cases, the person may be able to achieve the required field of vision to pass a driver’s test.