Abstract
Purpose:
Human corneas experience swelling while being stored in organ culture. Before corneal transplantation a deswelling process using hyperosmolar culture media is necessary. Deswelling should result in an optimal central corneal thickness (CCT) of approximately 550 micron to facilitate corneal transplant surgery by adjusting CCT to the recipient’s corneal thickness. Little is known about the role of endothelial cells in the osmotically induced deswelling process after organ culture. This study compares the deswelling kinetics of corneas with intact endothelium and disrupted or absent endothelium by measuring CCT over time using optical coherence tomography (OCT).
Methods:
10 human donor cornea pairs (donor age above 60 years) were cultured in MEM + antibiotics + 2% fetal calf serum for 21 up to 28 days. Right and left corneas were alternately assigned to one of two dehydration groups. Dehydration in the first group (Endothelial group = EG) was induced by using a serum-containing deswelling medium with dextran (MEM + antibiotics + 2% fetal calf serum + dextran 5%). Corneas of the second group (Non-Endothelial group = NEG) were dispensed from their endothelial cell layer using trypsinization (Trypsine 0,25% + EDTA 0,1% for 10 minutes at 39°C) and were then placed in the same dextran-containing deswelling medium. Disruption or absence of endothelial cell layer was demonstrated by microscopic photography. CCT was measured by OCT (Spectralis, Heidelberg Engineering) before deswelling (0 hours) and after 1, 2, 3, 6, 12, 24, 48, 72 and 144 hours.
Results:
Prior to deswelling CCT was 1070,97µm (±129,6µm) and 1133,8µm (±124,32µm) in the EG and NEG, respectively. Minimal corneal thickness was obtained after 24h in the EG (531,87µm ± 47,54µm) and 6h in the NEG (645µm ± 81,21µm). Final CCT after 144h was 561,7µm ± 52,1µm and 797,03µm ± 135,85µm, respectively. CCT was significantly (p<0,01) higher in the NEG than EG group after more than 6 hours.
Conclusions:
During the deswelling process an intact endothelial cell layer allows continuously low CCT-level over time. Corneal endothelial cells therefore play an important role in the deswelling process of human cultural corneas. It can be concluded that deswelling is a multifactorial process depending not solely on osmotic effects of the deswelling compound, but also on presence of an intact endothelial cell layer.
Keywords: 481 cornea: endothelium •
480 cornea: basic science