Precut tissue

The use of pre-cut tissue for Descemet stripping automated endothelial keratoplasty (DSAEK) provides a safe alternative to surgeon-cut grafts. Surgeons performing DSAEK have been asking for thinner grafts (<100 microns) based on reports of better visual outcomes after transplantation of such ultrathin grafts. According to results of a study reported at the 4th EuCornea Congress, the Gebauer SLc microkeratome is a reliable technology for safe dissection of ultrathin DSAEK grafts. “Variability in thickness of lamellae cut with available mechanical microkeratomes creates a challenge to reliably harvesting ultrathin grafts without risking donor perforation. Compounding this problem, the deeper microkeratome cutting heads that are required for dissecting the oedematous organ culture preserved tissues used by European eye banks are associated with higher standard deviation, resulting in greater discrepancies between requested and achieved thickness,” said Mor Dickman MD, University Eye Clinic Maastricht, The Netherlands.

The Gebauer SLc microkeratome is a motor-driven system that cuts ultrathin grafts with a single pass. It has an oscillating blade with a cutting speed of 10,000 rpm and a constant forward speed of 1.5 mm/sec along with a built-in applanation plate that allows adjustment of lamellar diameter.

Its performance for harvesting ultrathin DSAEK grafts and the effect of the dissection on endothelial cell viability was investigated in a study using 24 paired donor corneas considered unsuitable for transplantation for reasons other than endothelial pathology. The corneas were stored in organ culture medium (Minimal, Essential, Medium), underwent deswelling and then one eye of each pair was dissected and the fellow eyes were used as controls.

As measured by Fourier domain OCT, mean graft thickness was 65 microns right after dissection with a standard deviation of 13 microns. Mean graft thickness increased to 125 microns over the next 30 minutes and was unchanged during 2.5 days of storage in organ culture medium supplemented with six per cent dextran. Graft thickness was independent of both central corneal thickness measured prior to dissection and microkeratome slit width, said Dr Dickman.

Endothelial cell viability evaluated using trypan blue exclusion showed no significant differences in endothelial cell density (ECD) or morphology comparing the dissected and control corneas immediately post-dissection, 2.5 days later, or at any earlier time points.

Additional analyses of factors affecting endothelial cell viability showed lengthening of the interval between donor death and enucleation time was associated with faster ECD decline.

Mor Dickman: mor.dickman@mumc.nl