To examine the movement of air injected in the cornea in simulated deep anterior lamellar keratoplasty (DALK), from the needle tip to the formation of different types of big bubbles (BB) and to ascertain how air travels through the stroma and pre-Descemet's layer [Dua's layer (PDL)] to create a type-1 (air between PDL and deep stroma) and type-2BB (air between PDL and Descemet's membrane).