The deepest depths of the ocean have all sorts of strange creatures, such as glow-in-the-dark sharks, which have recently been found to have a highly advanced eye.

According to Live Science, such bioluminescent sharks have a dense group of light-sensitive cells in their retinas, allowing them to see more sophisticated light patterns in the deep dark depths they dwell.

The researchers published their work in the journal PLOS One.

"Every bioluminescent signal needs to reach a target photoreceptor to be ecologically efficient," study lead author Julien M. Claes, postdoctoral researcher at the Catholic University of Louvain in Belgium, said in a press release. "Here, we clearly found evidence that the visual system of bioluminescent sharks has co-evolved with their light-producing capability, even though more work is needed to understand the full story."

The sharks live about 200 to 1,000 meters below sea level in what is known as the mesopelagic twilight zone. At that depth, sunlight is but spotty bioluminescent emissions, creating dim surroundings.

"There are about 50 different shark species that are able to produce light - about 10 percent of all currently known sharks," Claes told Live Science.

The research team revealed that the bioluminescent sharks generate their unique features through hormones and not brain chemicals like melatonin used by other glow-in-the-dark bony fish. Their light-up feature is also used a camouflage mechanism that also acts as a hunting signal for members of the same species.

The researchers said these bioluminescent sharks have "faster vision," which would help them see quick changes in light more smoothly. Claes said his team will need to do more work to confirm their findings. However, they suggested these changes evolved in the sharks in cooperation with their bioluminescence.

For further studies, the researchers said they will need to examine the physical makeup of the sharks' retina and not just the sum of its parts.