Search

Before corneal transplant surgery, a deswelling process of organ-cultured corneas is required. This study compares the deswelling kinetics of corneas with an intact endothelial cell layer and disrupted or removed endothelium by measuring central corneal thickness (CCT) over time using anterior segment spectral domain optical coherence tomography.Ten donor pairs were cultured in organ culture. The right and left corneas were alternately assigned to one of 2 deswelling groups. Deswelling in the first group [endothelial group (EG)] was induced using a medium with dextran 5%. Corneas of the second group [nonendothelial group (NEG)] were deprived of their endothelial cell layer by trypsinization and were then placed in the same deswelling medium. CCT (mean ± SD) was measured by anterior segment spectral domain optical coherence tomography before deswelling (0 hours) and after 1, 2, 3, 6, 12, 24, 48, 72, and 144 hours. Deswelling kinetics was analyzed through the nonlinear platform in SAS/JMP11 Pro.Before deswelling, CCT was 1071.0 μm (±129.6 μm) and 1133.8 μm (±124.3 μm) in the EG and NEG, respectively. Minimum corneal thickness was obtained after 24 hours in the EG (531.9 ± 47.5 μm) and 6 hours in the NEG (645 ± 81.2 μm). CCT was significantly (P0.01) higher in the NEG than EG after more than 6 hours.Corneal dehydration after organ culture seems to be a multifactorial process, which not only depends on osmotic effects of the deswelling compound but also requires the presence of an intact endothelial cell layer.

Purpose Descemet membrane (DM) endothelial keratoplasty has improved outcomes of corneal transplantation in patients with corneal endothelial disease. However, the procedure has been criticized for jeopardizing donor tissue during graft preparation. Standardization of this procedure may provide a way toward minimizing tissue loss. For this purpose, we propose the use of a novel tool. Methods Computerized numerical control milling was used to create a blunt instrument, which was used to remove endothelial cells within a defined area in the periphery of donor corneas. Trypan blue was used to stain denuded DM. Graft preparation was continued as per our standard protocol. Transmission electron microscopy was performed on the treated area, and endothelial cell counts were obtained. Results Use of the modified procedure resulted in delineation of a peripheral band of denuded DM, which readily stained with trypan blue. This provided increased visibility of DM during subsequent steps. Transmission electron microscopy confirmed that no structural deficits of DM were induced. Mean endothelial cell loss (±SD) at 24 hours after preparation was 63 (±130) cells per square millimeter in the group prepared with the use of the new instrument (n = 7), versus 116 (±107) cells per square millimeter in the group prepared without the new instrument (n = 7; P = 0.45). Conclusions The device presented here enhances visualization of DM during creation of the peripheral margin for subsequent lifting of the margin and stripping of the graft. This may increase success rates and shorten preparation times and learning periods for DM preparation. DM ultrastructure and endothelial cells were not negatively affected.

Corneas are usually stored for a maximum of approximately 30 days in European cornea banks. Although attempts are being made to prolong culture periods, data on their success are extremely limited to date. The following study was carried out to describe the capacities and limits of the established system.Thirty-seven human corneas were stored foror = 12 weeks under standard eye bank conditions [modified minimal essential medium (MEM), 31 degrees C, closed system]. Twenty-one fresh human corneas served as control. Both the adenylate nucleotides and the glucose and lactate concentrations were measured in the tissue (all cellular layers) by using the bioluminescence technique. The endothelial-cell densities also were determined.Endothelial-cell densities decreased from 2,963.4 +/- 58.7 cells/mm2 (fresh) to 2,649 cell/mm2 after 4 weeks and to 2,087 cells/mm2 after 6 weeks. Storage for periods6 weeks led to total endothelial necrosis. Biochemical studies showed improving values during the first 4 weeks and acceptable conditions foror = 6 weeks.From these data, we conclude that long-term organ culture in a closed system is limited to approximately 6 weeks and thereby confirm the clinical results of Früh and Böhnke.

The purpose of this study was to obtain further information on the viability of organ-cultured human cornea. We thus used a specific staining method for succinate dehydrogenase (SDH), which is located in the membrane system of vital mitochondria. We examined fresh and long-term-cultured human corneas. After an initial incubation period in dextran-free culture medium, corneas were stored in a medium containing dextran. With respect to different appearances of the SDH staining, minimal essential medium without dextran seems to have a positive effect on the condition of epithelial cells. After renewal of the medium, keratocytes showed a brief improvement followed by a delayed deterioration, while the endothelial cells were severely damaged. However, best results for all three cell types were observed on the fourth day in a medium containing dextran. We therefore conclude that these corneas were best suited for transplantation.

PURPOSE Tenon plasty has been used to reconstruct the conjunctival surface in severe burns in which ischemic sclera was exposed or undergoing ulceration. A modified impression cytology procedure was applied to investigate the conjunctival epithelium. The quality of the regenerated epithelium on the advanced Tenon sheets was assessed. METHODS The 63 conjunctival samples of eye-burn patients were investigated. Among these, 41 patients had very severe bums. Conjunctival samples were collected from 6 weeks after surgery to 5 years after the accident. They were compared with conjunctival epithelia obtained from 53 normal eyes of healthy volunteers. A 25-mm2 Biopore membrane (Millipore Catalogue PICM 01250) was placed on the bulbar conjunctiva surface in the lower temporal quadrant, at a distance of 3-5 mm from the limbus, till it was soaked with fluid. The ablated cell sheets were stained with periodic acid-Schiff (PAS). RESULTS In all cases, an intact conjunctival epithelium was observed. In healthy eyes, 2,338 epithelial cells/mm2 and 155 goblet cells/ mm2 were found. Eyes after a surgical reconstruction with Tenon plasty resulted only in 1,575 epithelial cells/mm2 and 72 goblet cells/mm2. The differences were highly significant. The ratio of epithelial to goblet cell counts revealed an increase of goblet cells during the postoperative period. CONCLUSION Conjunctival epithelium as well as goblet cell densities were reduced after heat, lime, alkali, and acid burns. However, after concrete burns, cell densities were increased. Tenon plasty provided the regeneration of the fully intact conjunctival epithelium. Goblet cells were present from 6 weeks after the surgery on; their number increased gradually. The stimulation of the goblet cell mucous secretion is discussed.