TRANSPLANTATION

Endothelial keratoplasty using a pre-Descemetic graft is being looked to as the future in endothelial keratoplasty. Focusing on the development of pre- Descemetic automated endothelial keratoplasty (PDAEK), corneal specialists at the University Eye Clinic, Maastricht, The Netherlands, have established proof of concept that safe, standardised harvesting of planar, pre- Descemetic grafts is possible using the Gebauer SLc Expert microkeratome system. Mor Dickman MD, reported on the study at the 4th EuCornea Congress, Amsterdam.

EASIER HANDLING
“Pre-Descemetic grafts are expected to provide the same visual results as DMEK grafts since they are very close in thickness. However, because the pre-Descemetic grafts have added stromal support, they should offer easier handling and possibly better graft adhesion. Automated donor preparation of pre-Descemetic grafts is desirable because manual dissection requires advanced surgical skills. However, the use of existing microkeratomes has been limited by poor thickness predictability. In addition, the previously available technology cuts grafts with a meniscus profile that contributes to a hyperopic shift, and it has been unclear how forces applied during mechanical harvesting might affect endothelial cells,” said Dr Dickman.

“We have established the possibility for reproducible automated Pre-Descemetic graft harvesting. Now, clinical studies are needed to evaluate patient outcomes.” The Gebauer SLc expert microkeratome can dissect corneal lamellae of any desired thickness in the range between 30 and 950 microns with a diameter of 9.5mm. It uses vacuum applanation to fixate the cornea and can be fit with rigid reference members (RRMs) that are profiled to correct for differences between peripheral and central corneal thickness in order to create planar grafts.

The performance of the Gebauer SLc Expert for harvesting pre-Descemetic grafts was investigated using organ-cultured human corneas unsuitable for transplantation. Measurements made using Fourier domain OCT showed mean intended central graft thickness was 32 ± 6 microns and the mean achieved thickness was 44 ± 7.7 microns. Use of the RRMs resulted in grafts that were almost perfectly planar. Assessment for endothelial damage performed by Zhigou He PhD, and colleagues at Laboratoire BiiGC, France, showed satisfactory viability and morphology of the central endothelial cells.

REFRACTIVE SURGERIES
The investigators also demonstrated the feasibility of using the microkeratome to prepare 25 micron thick Bowman grafts. “With the Gebauer SLc Expert, we can optimise tissue use by obtaining a graft for endothelial keratoplasty as well as material from the anterior cornea that can be used for ocular surface and refractive surgeries,” said Dr Dickman.

He noted that manually harvested Bowman grafts have recently been described for treating keratoconus. These grafts can be used as a scaffold for epithelial regeneration in vivo and epithelial/endothelial cultivation in vitro and may prove useful for treating neurotrophic ulcers as well as for refractive purposes.