: The rest of your thoughts about the Pfhor's third eye being useful for better
: peripheral vision are fine, but depth perception doesn't have anything to
: do with "cone of vision". Two eyes give us depth perception
: because the difference in angle between objects and each of the two eyes (
: parallax ) can be used to gauge distance. The same effect could be
: accomplished by weaving side to side and comparing how things look at each
: end of the weave (closer things will appear to move more, distant things
: less), but two eyes lets us do that without actually moving our heads, as
: we can just see from two places at the same time.
Alternatively, like many early amphibians and reptiles, the Pfhor use the upper eye as a heat/light sensor. Many early amphibians and reptiles had a smaller third eye embedded in the tops of their heads that wasn't used for vision in the normal sense, but was sensitive to light and heat, allowing them to gauge the time of day and regulate their body temperature. It's possible (maybe) that the evolutionary line leading to modern Pfhor never lost this extra eye, unlike the tetrapod lines of Earth. Maybe the Pfhor homeworld was more prone to fluctuating temperature changes, and assuming the Pfhor are cool-blooded (???) then knowing where the best spot to warm up at would be important. As for the (,',) vs. (',') eye arrangement, maybe that represents racial/species differences?