Many animals have an area in their retinas where their photoreceptors (and the attendant neurons) are densely packed, increasing the resolution of their vision. This region goes by many names. In invertebrates, it’s called an acute zone. In vertebrates, it’s an area centralis. If that area is also inwardly dimpled, as it is in our eyes, it’s a fovea. For all our sakes (except the vision scientists, to whom I apologize), I’m just going to stick with acute zone. In humans, it’s a bullseye—a round spot in the center of our visual field. It’s what you are training upon these letters as you read
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