How does the risk for diplopia in vary in different animals?

Updated: May 21, 2019
  • Author: Jitander Dudee, MD, MA(Cantab), FACS, FRCOphth; Chief Editor: Andrew G Lee, MD  more...
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Unless the visual fields of the eyes overlap, binocular diplopia cannot occur. Among vertebrates, the potential for diplopia (and for stereoscopic depth perception) depends on where the eyes are located in the head. Eyes located on either side of the head provide a wide visual field but with a less overlapped visual field. These animals have less field for binocular vision and less risk for diplopia when one eye becomes misaligned. However, when both eyes are located in the front of the head, a greater visual field overlap exists and, thus, a better binocular depth perception, as frequently seen in predators. Misalignment of such eyes may result in diplopia.

The eyes of birds demonstrate many unique anatomical features, one of which is the presence of multiple foveae and, in some cases, a streak fovea linking 2 foveae. Thus, they may be able to have 2 separate areas of regard without disabling diplopia. How the visual perception occurs in these cases remains debatable.

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