The black lesion is a descemeocoele where a corneal ulcer has perforated through the stroma to leave only descemet’s membrane bulging forward. The black appearance indicates that iris is protruding into the ulcer giving a staphyloma. The central cornea of the pug has limited sensation so that a corneral ulcer can go un-noticed until it is very severe, as in this animal. Treatment is surgical and the best operation is either a full thickness graft or more likely a corneoconjunctival transposition graft as described in the cat by Andrews and colleagues(Corneoconjunctival transposition for the treatment of feline corneal sequestra.
Vet Ophthalmol. 2001 4:107-11). This dog shows the result possible when this surgery is used in such a situation.