Optimizing pre-Descemet endothelial keratoplasty technique.

Pre-Descemet endothelial keratoplasty (PDEK) is an alternative technique to Descemet membrane endothelial keratoplasty (DMEK). The preparation of PDEK tissue by pneumatic dissection is simple and reproducible. The PDEK clamp helps to consistently obtain a type 1 big bubble. The mean size of type 1 big bubble is 7.255 ± 0.535 × 6.745 ± 0.668 mm. The volume of air required to obtain type 1 big bubble is 0.14 to 0.37 mL. Dissection of PDEK tissue can be achieved by trephination or manual excision. Insertion of tissue into the recipient eye can be by injection or pulling. Unfolding techniques used for PDEK are similar to those used in DMEK. Unlike DMEK, PDEK tissue is easier to handle and unscroll and allows use of younger donors. It could help surgeons converting to endothelial keratoplasty, with significant advantages in preparation, handling, and unscrolling in the eye.

Deep anterior lamellar keratoplasty: dissection plane with viscoelastic and air can be different.

AIMS: To investigate and define the nature of big bubbles (BB) formed by injection of viscoelastic in deep anterior lamellar keratoplasty. METHODS: Intrastromal injections of 0.1 and 0.3 mL of sodium hyaluronate 1.2% and 0.6% were made into sclera-corneal discs (n = 32) at superficial (anterior-third), midstromal (middle-third) and deep (posterior-third) levels to simulate deep anterior lamellar keratoplasty. Postinjection optical coherence tomograms (OCT) were obtained with the needle in situ. The samples were sectioned and examined histologically. Twelve control samples were injected with air. RESULTS: With superficial injections (n=8) only intrastromal accumulation of viscoelastic was noted. With midstromal injections (n=10) intrastromal accumulation of viscoelastic (n=6) and intrastromal big bubbles (IBB) (n=4) with substantial and variable stromal tissue in the walls were noted. No type 1, type 2 or mixed BB were noted. With deep injections (n=14), type 1 BB (n=4), IBB (n=4) and mixed BB (n=6) were obtained.There was no difference in the results with the two different concentrations of viscoelastic used. With air injection (n=12), 10 type 1 and 1 type 2 BB and 1 mixed BB were obtained. No IBB was noted. CONCLUSIONS: BB obtained by injection of viscoelastic and air can be different. The former tends to occur at the site of injection, especially with midstromal injections, takes the form of tissue separation by stretch and tearing and does not cleave in a consistent plane like air. Surgeons should be aware of IBB created by viscodissection and not confuse it for a type1 BB. Intraoperative OCT should help identify IBB.