Big bubble deep anterior lamellar keratoplasty: the collagen layer in the wall of the big bubble is unique

Purpose In big bubble ( BB ), deep anterior lamellar keratoplasty intracorneal injection of air separates Descemet's membrane ( DM ) and the pre‐Descemet's layer (Dua's layer [ DL ]) to create a type 1 BB . We tested the hypothesis that air injection after excision or ablation of DL will fail to produce a BB . Methods Nine human sclero‐corneal discs were used. Three served as controls. In three, a type 1 BB was created, the bubble wall was excised and more air injected in an attempt to create another BB . In three samples, the DM was removed and 22 μ of posterior cornea were ablated by phototherapeutic keratectomy ( PTK ). Air was injected to induce formation of a BB . Tissue from these experiments was subjected to light and electron microscopy. Results In all three control eyes, a type 1 BB ( DL  +  DM ) was obtained. Air injection after excision of the type 1 BB wall in three samples failed to produce another BB . Following PTK of DL , injection of air failed to create a BB in all three samples. Multiple points of air leak from the deep stroma were observed in all six samples. Light and electron microscopy showed a clear distinction between the ablated and non‐ablated areas of cornea. Conclusions This study supports the hypothesis that a BB cannot be created once the DL is excised or ablated. This adds to evidence that DL is unique. It also demonstrates that DL is not a random separation of deep stroma of the cornea.