fovea

A small depression in the retina of the eye where visual acuity is highest. The center of the field of vision is focused in this region, where retinal cones are particularly concentrated.

Her eyes strained, magnifying the view as best they could; she could feel rings of tiny muscles warping the lenses in each eye, while other filaments altered the shape of her foveae.

Definition from Kindle (The New Oxford American Dictionary)