Whales have developed a special adaptation for their eyes to withstand the high pressures of the deep sea. To focus, the whale moves its eye outward thanks to a tissue located behind the eye, surrounding the optic nerve, called the corpus cavernosum. It has large vessels and many elastic fibers. Humans don't have this tissue in their eyes because we don't move our eyes forward when we focus, but whales do.
Whale eyes are very well adapted to pressure changes with a thick, hard shell-like structure, the sclera, 4 cm thick, which protects the retina from deforming when the eye moves out of its socket to focus.
Blood clots into regular structures, and its red blood cells are similar in size to human red blood cells.
You can compare in the two textured drawings the thickness of the whale sclera compared to the thin sclera of humans (6) and the corpus cavernosum located around the optic nerve (7) present in whales, but not in the human eye.
Diagram of the parts of the human eye marked with numbers:
1.- Cornea: transparent, protects the eye, controls focus and entry of light.
2.- Iris: with color, regulates the entry of light.
3.- Crystalline: transparent lens, helps to focus.
4.- Retina: light-sensitive tissue.
5.- Optic nerve: transmits the visual message from the eye to the brain.
6.- Sclera: white part of the eye, gives it shape and protects it
