Corneal transplantation using 4-week banked donor material. Long-term results

Lower risk of graft dislocation applying organ cultured corneas compared with cold short-term cultured corneas during DSAEK surgery

BACKGROUND

To investigate factors that may affect graft dislocation after uneventful Descemet stripping endothelial keratoplasty (DSAEK), with a special focus on different donor cornea storage conditions.

METHODS

All DSAEK surgeries performed during 6 years in our hospital were retrospectively investigated. Patients with previous intraocular surgeries other than cataract extraction were excluded. Donor data (age, gender, death-to-preservation time, cornea storage conditions, graft storage time, and estimated thickness of the graft) and patient information (age, gender, and indication for surgery) were noted.

RESULTS

A total of 26 dislocations (6.6%) out of 394 DSAEK surgeries were found. The dislocation rate was considerably reduced between 2011 and 2016, due to more experienced surgeons. There was a significantly higher dislocation rate with the use of donor corneas stored in cold storage solution (12.7%) compared with organ culture solution (2.5%) (P < 0.001). During the study period, donor corneas stored in cold storage solution and organ culture solution were applied in 158 (40%) and 236 (60%) cases, respectively. There were no differences in recipient age and gender between patients who received corneas from the two storage systems, indicating a random distribution of grafts. In a multivariate analysis, only operation year (reduced rate over the years) and cold storage solution were statistically significantly associated with graft dislocation.

CONCLUSION

This study suggests that the type of storage solution may have a decisive role in graft dislocation in DSAEK surgery.

Clinical Transplantation of Individualized Recipient Serum-Adapted Cornea Reduces the Risk of Graft Rejection after Keratoplasty

Corneal diseases cause severe visual impairment that necessitates corneal transplantation and frequently repetitive procedures due to graft rejection. We tested the hypothesis that exposure of donor corneas to recipient serum-derived factors during eye banking triggers a preoperative adaptation that is beneficial for postoperative tolerance. Donor corneas were incubated in a medium containing human serum (HS) obtained in each case from the prospective graft recipient in order to individually expose the donor cornea to the recipient's serum. All recipient serum-adapted corneas (RSACs) fulfilled the clinical criteria required by the national law and were transplanted successfully. The postoperative ophthalmological examination extended up to 8 years. All RSACs were tolerated by their recipients and did not cause postoperative complications and no rejection. Proteomic analysis of corneas cultivated in culture medium containing either fetal calf serum (FCS) that is routinely used for cornea banking or HS revealed different patterns of proteins. HS-cultured corneas showed a greater proteomic similarity with native human corneas than did the FCS-cultured corneas, indicating a differential nutrification of the cultured corneal tissue by HS-derived factors. The clinical results show for the first time that postoperative complications such as tissue intolerance and graft rejection might be managed if the corneal tissue is individually adapted to the recipient's serum trophic factors. This new donor tissue treatment procedure offers incontrovertible advantages and could be adapted for low-risk eyes as well as other transplantable tissues.

Impact of organ culturing on metabolic profile of human corneas: preliminary results

PURPOSE

It is suggested that the quality of corneal graft may depend on modifications that appear in the tissue during culturing. The aim of this study was to investigate the differences in the metabolic profile between cultured and noncultured human corneas.

METHODS

Corneas from 12 donors were obtained post-mortem and cultured for 6-20 days. Control corneas were obtained from four patients with malignant melanoma of the chorioidea and were kept frozen at -80 °C until analysed. The metabolic profiles of the samples were investigated using high-resolution, magic angle spinning (1) H nuclear magnetic resonance spectroscopy and special software for: (i) analysis of complex mixtures, (ii) principal component analysis and (iii) specialized statistical analysis.

RESULTS

Twenty metabolites were detected and assigned in the corneas. Significant differences in metabolic profiles between cultured and noncultured corneas were revealed. It was also shown in samples kept in culture for 9-14 days that the levels of (i) alanine, formate, lactate and (ii) acetate, alanine, arginine, lactate were elevated in comparison with the samples kept for <9 and more than 14 days, respectively.

CONCLUSIONS

Corneal culturing affects the metabolic profile of the tissue. The increases in the levels of some metabolites within the second week of culturing likely result from variations in tissue metabolic or enzymatic activity caused by changed (organ culture) environment. As the mechanisms responsible for these changes are not clear, further research is indicated.

Eye bank issues: II. Preservation techniques: warm versus cold storage

Most of the tissue used for penetrating keratoplasty is issued through eye banks that store the corneoscleral button either in hypothermic storage at 2-6 degrees C or in organ culture at 31-37 degrees C. These two preservation techniques differ in technical aspects, tissue evaluation possibilities, storage time and microbiological safety. Hypothermic storage is simple and requires little expensive equipment. In general a pre-storage evaluation of the endothelium is performed by specular microscopy and storage time is usually around 7-10 days. Organ culture is a relatively complicated technique requiring more expertise and well-equipped facilities. Evaluation of the endothelium is not only performed before storage, but is routinely performed after storage through the use of light microscopy. With organ culture the allowed storage period is longer, up to four weeks. The vulnerability of organ culture to microbial contamination can be turned into an advantage because it allows the detection of residual micro-organisms on the cornea before surgery. Both preservation techniques seem to result in similar graft survival. The method of choice for preservation of the donor cornea is dictated by a number of factors mentioned in this review and this helps to explain the geographical differences in the use of the different techniques.

Sterile structural imaging of donor cornea by optical coherence tomography

PURPOSE

The purpose of the study was to demonstrate a new noncontact method for sterile measurement of structure and thickness of donor cornea with use of optical coherence tomography (OCT).

METHODS

A commercially available OCT instrument designed for retinal measurements was used for noncontact assessment of human corneas. Structural changes occurring during organ culture were evaluated in 29 corneas. Comparison with histology was performed, and the ability of OCT to detect corneal scars and corneal thickness was investigated.

RESULTS

Corneal epithelium, stroma, and posterior curvature, as well as thickness, can be measured by standard OCT while the cornea remains in its storage bottle. Epithelial changes leading to a reduction of epithelial thickness, stromal structural changes, and hydration folds can be visualized. OCT scans correlate well with histology. Preexisting and developing corneal scars can be detected by OCT.

CONCLUSIONS

Corneal structural imaging can be performed under sterile conditions by OCT. This provides a method for improvement of corneal storage and a screening method for signs of photorefractive surgery and scarring in donor cornea.

A method for registration of toxic drug effects on corneal endothelium. Effect of gentamicin on rabbit corneal endothelium

A weight recording system (Medin & Davanger 1988, 1989), was used to demonstrate possible toxic damage of a medicament to the endothelium of rabbit corneas stored in organ culture. Seven corneas were stored in organ culture medium containing gentamicin (3.0 mg/ml). Seven other corneas stored in identical organ culture medium without gentamicin served as controls. The corneas were followed with weight recordings for up to 76 h. A toxic effect of gentamicin was demonstrated by a rapid weight increase in the corneas stored in the presence of gentamicin. After 5.3 h there was a significant difference (P = 0.0002) between the average weights of the two groups, and this difference increased during the following 2-3 days. Corneas from the two groups were also examined by light microscopy and scanning electron microscopy. There was good accordance between the weight recordings and the morphology. The weight recording system detects clearly the toxic effect of gentamicin (3.0 mg/ml).

Some metabolic changes during human corneal organ culture

In order to evaluate the changes in medium composition during closed system corneal organ culture at 30 degrees C, pH, pO2, glucose and lactate was measured 1 to 7, 14 and 28 days after incubation of a total of 49 human corneas. During organ culture pO2 decreased from 17.3 kPa to 8.8 kPa at day 28. The average oxygen consumption was initially 0.16 mumole/h/cm2, but decreased rapidly to an average of 0.04 mumole/h/cm2 during the first weeks of incubation. The glucose concentration fell from 5.1 mM to 0.25 mM after 28 days, and the lactate concentration rose from 2.5 mM to 11 mM. The concentration changes were for both substances highest during the first 14 days of organ culture. The pH fell from 7.36 to 6.64 after 28 days. These findings indicate that the cultured human cornea predominantly metabolizes glucose anaerobically, and that the metabolic activity decreases during incubation. The limiting metabolic factors for prolonging the culture period seem to be development of severe acidosis and glucose depletion in the medium.

The influence of donor age and post mortem time on corneal graft survival and thickness when employing banked donor material (A five-year follow-up)

Sixty-three consecutive corneal transplantations employing banked donor material were grouped according to donor age and post mortem time, respectively, and followed at regular controls for 5 years. Twenty-six cases (38% belonging to a risk group i.e. had earlier had corneal transplantation(s) and/or vascularized corneas) with a mean donor age of 55.8 years were compared with 37 cases (35% at risk) with a mean donor age of 75.7 years. The five-year graft survival was 72.0% in the first group and 86.3% in the second group, however, the difference was statistically insignificant. In 27 cases (26% at risk) with a mean post mortem time of 17.4 h a five-year graft survival of 81.0% was found compared with 80.3% for 36 cases (44% at risk) with a mean post mortem time of 40.5 hours. No difference in graft thickness was demonstrated between any of the groups, and in all cases with surviving grafts normal values for corneal thickness were achieved. It is concluded that neither donor age nor post mortem time are limiting factors when selecting donor material for organ culture and corneal grafting.

Irreversible immune reactions following keratoplasty. Retrospective clinical and histological evaluation of graft failure in a material of 206 consecutive eyes

A total of 16/206 eyes in 14/186 patients developed irreversible immune reactions. 15 of the rejected eyes belonged to the 'classical' risk groups, i.e. systemic immune disorders (3/3), metaherpetic keratitis (6/41), pseudophakic bullous keratopathy with inflammation (2/6), non herpetic keratitis with vessel invasion (1/23) and 3 regrafts not included in these groups (a total of 7/31 regrafted eyes rejected). Only 1 rejection occurred in the low-risk groups: an aphakic eye with bullous keratopathy. Histopathological examination revealed that discs which later developed irreversible immune reactions had invariably been grafted in eyes which had vascular invasion and/or inflammation of the recipient cornea. In all, 55/206 eyes ended up with opaque grafts, i.e. irreversible immune reactions were responsible for about one third to one-quarter of the graft failures in the present material. The irreversible immune reactions in the material must be considered 'minimum values', since possible abortive, torpid immune reactions may have escaped recording.

Treatment of central corneal ulcers by à chaud transplantation of organ culture preserved donor tissue

In the period 1979-83 a total of 232 penetrating corneal transplantations were performed with organ culture preserved donor material. Forty-two operations were made à chaud for central corneal ulcerations. The results of these interventions are reported and discussed. The surgery presented no serious problems and on first post-operative day the anterior chamber was reformed in all cases, and pain was relieved. Patients were confined to bed only for 1 day. Graft deswelling was slightly retarded compared to planned surgery, but all functioning grafts obtained normal thickness. The overall graft survival rates after 6, 12 and 18 months were 66, 53 and 48%, respectively. For herpetic ulcers the survival after 18 months was 49% and for non-herpetic ulcers 47%. The grafts failed in all cases where it had been necessary to employ grafts of more than 10 mm. This latter group was comprised of the non-herpetic cases; were they excluded, the graft survival rate would increase to 60%. Among cases with a clear graft the median visual acuity after 18 months was 0.33 (range less than 0.1-0.67). Excluding cases with a non-corneal cause of visual reduction, the median visual acuity was 0.4 (range 0.33-0.67). It is concluded that grafting can be successfully employed in the treatment of central ulcers, as it not only restitutes tissue integrity, but also preserves useful vision.

Post mortem HLA-DR typing of donor corneas using DNA-hybridization technique

With donor material kept under banking conditions, corneal grafting is today an elective routine surgical procedure. Increasing evidence suggests that the clinical results may be improved by HLA matching. However, serological tests require that a blood sample be taken while the donor is still alive or shortly post mortem. We report HLA-DR donor typing with a DNA hybridization technique using DNA isolated from the donor eye more than 24 h post mortem. The practical implications of this procedure are briefly discussed.