A new body part has been discovered and it's literally as clear as the naked eye.

In a report published in the academic journal “Ophthalmology,” researchers revealed they've found a new layer to the human eye. Named Dua’s layer, after professor Harminder Dua from the University of Nottingham in the U.K. who discovered it, the previously undetected sixth layer of the eye measures just 15 microns thick (more than 25,000 microns equals 1 inch). Despite its microscopic size, the discovery means a huge change in ophthalmology, Dua said.

“Ophthalmology textbooks will literally need to be rewritten,” Dua said in a statement. "From a clinical perspective, there are many diseases that affect the back of the cornea, which clinicians across the world are already beginning to relate to the presence, absence or tear in this layer."

The cornea is a transparent layer that forms in front of the eye. Until now, ophthalmologist textbooks identified only five layers of the human cornea, according to Discovery News.

The discovery was made using tiny bubbles of air to separate the different layers of the cornea. The scientists studied the layers using electron microscopy, which allows viewing at up to 1,000 times normal size. The discovery can help surgeons understand diseases in the cornea such as acute hydrops, descematocele and pre-descemet's dystrophies.

Since the discovery, scientists now believe that patients with keratoconus, an eye disease where the cornea bulges and becomes cone-shaped, is caused by a tear in the Dua layer.

Back in 2011, scientists at the University of Hawaii discovered light-detecting cells in a marine animal that helps them understand the evolution of the human eye.

"This research provides a new model for understanding the very earliest stages of eye evolution, how simple cells on the surface of an animal could become able to respond to light, and how these simple cells could be connected to eventually form something as complex as the human eye," Dr. Yale Passamaneck, lead author of the research team, said in a statement.

Scientists have hypothesized that the human eye evolved from a simple patch of cells on the surface of a primitive animal. The cells slowly grew in complexity, adding features such as pigmentation, a lens and neural connections to the brain. Until the 2011 discovery, few of these stages had been identified.