Pitch discrimination is thus dependent on the region of the basilar membrane that vibrates maximally to sounds of different frequencies. Pitch discrimination is enhanced by lateral inhibition. Because of refraction, the image on the retina is upside down and right to left. The right half of the visual field is projected to the left half of the retina in each eye, and vice versa. Accommodation is the ability to maintain a focus on the retina when the distance between the object and the eyes is changed.
Accommodation is produced by changes in the shape and refractive power of the lens.
This gives the lens a low refractive power for distance vision. As an object is brought closer than 20 feet from the eyes, the ciliary body contracts, the suspensory ligament becomes less tight, and the lens becomes more convex and more powerful. Visual acuity refers to the sharpness of the image. It depends in part on the ability of the lens to bring the image to a focus on the retina. The retina contains rods and cones, photoreceptor neurons that synapse with bipolar cells.