The history of this eye: A corneal ulcer formed. The ulcer produced a minute perforation of the cornea. The aqueous humor rushed towards the site of perforation and carried the iris with it.
The iris plugged the perforation and became incorporated with the scar issue healing process. Notice the iris pigment that is incorporated in the corneal scar -evidence of iris involvement and thus, an adherent leukoma.
Fortunately, this eye recovered from this potentially catastrophic situation. Other eyes might have gone on to staphyloma, glaucoma,endophthalmitis, panophthalmitis and / or phthisis bulbi from the same initial corneal ulcer.