You can read about it here:
http://en.wikipedia.org/wiki/Dua%27s_layer
Dua's layer is a newly discovered layer of the human cornea proposed in a scientific article in June 2013.[1] It is 15 micrometres (0.00059 inches) thick and is located between the corneal stroma and Descemet's membrane. It is the sixth layer of the cornea to be discovered