Figure 9. .

Offset placement of bilateral sector prisms can avoid diplopia. This is illustrated for a gaze 20° into 20Δ sector prisms. The OD prism has the conventional 6° offset from primary gaze, while the OS prism is offset the additional 11° of the prism power. Although field extent is identical, the pericentral scotoma of the conventional bilateral fitting (Fig. 5) is gone, as is the diplopic area of unilateral fitting (Fig. 8), though central confusion remains. (A) Simulated Goldmann (with head straight). (B) The percept diagram shows that a region of visual confusion exists where OD is viewing through a prism and OS is not. The apex of the leftmost triangle in each diagram identifies the location of the OS prism apex.