Purpose To introduce a modification to big-bubble deep anterior lamellar keratoplasty (DALK) which can decrease the risk of Descemet membrane (DM) perforation during air injection.

Method In Anwar's big-bubble technique, a 27-guage needle is inserted from the trephination site and advanced into the corneal stroma up to the centre. The technique we introduce modifies the original technique in the following fashion. After trephination to approximately 80% of corneal thickness, a 27-guage needle is inserted into the stroma peripherally from the trephination site towards the limbus. Air is injected gently into the deep stroma until a big bubble is formed. This technique was performed in 16 consecutive keratoconic eyes undergoing DALK. Additionally, peripheral air injection was carried out in 27 eye-bank corneas using a peripheral approach.

Results In all (100%) eye-bank and 13 (81.3%) live corneas, a successful big bubble was easily achieved following peripheral air injection. In these 13 live corneas, all bubbles were formed at the central (n=10) or paracentral (n=3) cornea and extended centrifugally (type 1 bubble). In one of these corneas, an additional three bubbles were noted in the periphery between the DM and the pre-Descemet posterior stromal layer (Dua's layer, type 2) after a type 1 bubble was formed. In two live corneas in which peripheral air injection failed, a big bubble was successfully formed after air was injected inside the trephination site.

Conclusions Air injection peripheral to the trephination site is a reproducible modification to the standard technique which can decrease the risk of DM perforation during air injection.