In anticipation of Discovery Channel’s Shark Week, we decided to take a dive into the big blue and examine just how comparable a shark’s eyes are to the human eye. The shark’s eye structure, much like other vertebrates, contains a cornea, lens, retina, pupil and iris. Given their similar structure and usage, shark eyesight works similarly to that of humans.
In sharks and humans, the amount of light entering the eye is controlled by the iris. The iris contracts muscles to dilate the pupil. This is a vitally important ability for sharks as many parts of the ocean consist of low light conditions. Many deep-sea sharks are permanently dilated to best absorb what little light permeates these depths.
As in humans, sharks have the two basic types of retinal cells – rods and cones. While it was previously thought that the rods in conjunction with the cones only provided a grainy and poorly detailed image for the creature, science has now proven that not to be the case. While it’s not entirely clear how sharks interpret color, studies indicate that most sharks have the retinal mechanisms for acute color vision. In fact, the rod-to-cone ratio of the Great White Shark is the most alike that of humans, 4:1.
The cornea, responsible for the majority of the sharks focusing power, is one piece of the eye that most resembles that of a human. Scientists are studying the structure of the cornea in the interest of someday using this part of the shark’s eye in human transplantation. Studies are also being conducted in order to help experts learn how better to treat human corneal disease.
While the ocean is still a foreign and alien world to humans, we find ourselves fascinated by the creatures that inhabit these waters. Thanks to the brilliant minds responsible for these scientific and medical advancements, humans and sharks may turn into allies, yet.