Q.Name the region of retina where rods and cones are absent.

The paired eyeballs sit in the bony orbit, protected by eyebrows, eyelids, eyelashes and lacrimal glands, moved by six muscles. The eyeball wall has three layers: the outer sclera (dense fibroelastic tissue, its transparent anterior bulge the cornea, avascular and nourished by aqueous humor, covered with conjunctiva); the middle, vascular, pigmented choroid (with the choroid proper lining the sclera, the muscular ciliary body secreting aqueous humor and holding the lens via suspensory ligaments, and the perforated, pigmented iris controlling pupil size); and the inner retina. The biconvex, elastic lens, suspended by ligaments, separates an anterior aqueous chamber from a larger posterior vitreous chamber and fine-focuses light (accommodation). The retina's inner nervous layer has an outer photoreceptor layer (rods -- rhodopsin-based, dim/scotopic vision; three cone types -- red/green/blue, bright/photopic colour vision), a middle bipolar-ce …