FIGURE 11.

Various configurations of the mirror prism-like elements used as a field expansion device for homonymous hemianopia. (A) Spitzberg’s mirror prismatic device was designed as a single element unilateral sector prism field expander that extends vertically across the whole lens. While the prismatic deflection angle can be large, the field of view seen through this “prism” is narrow and constrained by the thickness of the carrier spectacle lens. (B) The field of view can be expanded by creating a Fresnel-like structure with segments of these elements placed one next to the other. Short elements of this type can then be used to implement the peripheral prism design. (C) Tilting the same series of mirror elements can be used to implement the oblique peripheral prism design with a higher deflection power.