Our ability to see in three dimensions has been an evolutionary advantage in the past in terms of hunting. When looking at humans and other animals which are classed as "predators", in the sense that they need to hunt other animals to survive, their eyes tend to be more on the front of their head, which gives them an overlap in their vision allowing them to see in 3D. This sacrifices the field of vision (FoV) that we have, but allows us to have a greater perception of how far away something is. In contrast, animals which are often classed as "prey" tend to have eyes which are wider apart, giving them a larger area which they can see, but they can't see depth as well due to this. 

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The optometrist can test how well you can see in 3D by using a couple of different tests. The most common of these is called TNO, and involves wearing a pair of glasses which are red in one eye, green in the other and having to see which piece of a circle is missing. There are a few other ways that this can be done though!