The thinned-out portion of the retina where only the cones are densely packed is

At the posterior pole of the eye lateral to the blind spot, there is a yellowish pigmented spot called macula lutea with a central pit called the fovea centralis. The fovea is a thinned-out portion of the retina where only the cones are densely packed. It is the point where visual acuity is the greatest.