Donor organ cultured corneal tissue selection before penetrating keratoplasty

Descemet Membrane Endothelial Keratoplasty With and Without Graft Deswelling: A Prospective Clinical Study

PURPOSE

The purpose of this study was to assess whether omission of dextran from corneal organ culture medium alters the outcome of Descemet membrane endothelial keratoplasty.

METHODS

Participation in this single-center, multisurgeon, prospective, randomized, comparative clinical trial was offered to patients scheduled for Descemet membrane endothelial keratoplasty between April 2020 and May 2022. Patients received grafts from corneas deswollen in organ culture medium-containing 6% dextran T-500 or from corneas that were not deswollen. Corrected distance visual acuity (CDVA), graft detachment, central corneal thickness (CCT), and corneal endothelial cell counts were measured at different time points up to 12 months postoperatively.

RESULTS

Grafts stored with dextran were transplanted in 92 patients, and grafts stored without dextran were transplanted in 102 patients. Mean donor age and endothelial cell counts did not differ significantly between both groups. Mean (±SD) postmortem time in hours was 23.9 ± 11.8 in grafts that were deswollen and 28.2 ± 13.8 in grafts that were not deswollen (P = 0.02). The groups did not show any significant difference at baseline regarding sex, CDVA, or CCT. In the group with dextran, patients had a mean age of 72.5 ± 9.9 years versus 69.5 ± 8.7 in the group without dextran (P = 0.03). CDVA improved and CCT decreased significantly in both groups. No differences were detected between the groups regarding CDVA, CCT, endothelial cell counts, or rebubbling rates.

CONCLUSIONS

This study did not detect any evidence that the omission of dextran from organ culture medium negatively affects the outcomes of Descemet membrane endothelial keratoplasty.

Long-term outcomes of deep anterior lamellar versus penetrating keratoplasty for keratoconus

AIMS

To compare the long-term outcomes of deep anterior lamellar keratoplasty (DALK) with penetrating keratoplasty (PK) in keratoconus.

METHODS

Retrospective comparative case series (228 DALKs and 274 PKs). A biphasic linear model was used to describe the postoperative outcome of the endothelial cell density (ECD). Visual acuity, specular microscopy, corneal topography and optical coherence tomography findings were recorded.

RESULTS

Graft survival of the 502 keratoconus eyes was 96.7 at 10 years and 95.6% at 20 years. Visual acuity improved from 20/378±5.1 lines preoperatively to 20/32±2.1 lines at 30 months. The corneal ECD decreased from 2494±382 cells/mm2 to 1521±659 cells/mm2 at 10 years. The mean simulated keratometry increased from 44.88±2.54 D at 1 year to 46.60±3.0 D at 3 years. The mean follow-up was 103.4 months for DALKs and 106.1 months for PKs. The cumulated incidence of postoperative ocular hypertension requiring treatment was significantly higher in PKs than in DALKs. The early- and late-phase rates of ECD loss were significantly lower in DALKs than in PKs. These figures in DALKs were 50% of those observed in PKs. The simulated mean keratometry was significantly higher in DALKs than in PKs in the mid but not in the long term. No significant differences in visual acuity were observed between both groups. Manual dissection-DALK featured slower visual recovery than PK and big bubble-DALK, whereas big bubble-DALK and PK featured similar visual recovery.

CONCLUSIONS

DALK featuring higher endothelial survival and lower risk of postoperative ocular hypertension may be superior to PK when indicated for keratoconus.

Endothelial failure and rejection in recipients of corneas from the same donor

Objective

To determine whether patients who receive corneas from the same donor have similar risks of endothelial failure and rejection.

Methods and Analysis

Patients with Fuchs endothelial dystrophy (FED) and pseudophakic bullous keratopathy (PBK) who received their first corneal transplant between 1999 and 2016 were analysed. Patients receiving corneas from donors who donated both corneas for the same indication were defined as ‘paired’. Gray’s test was used to compare the cumulative incidence of endothelial failure and rejection within 5 years post-transplant for ‘paired’ and ‘unpaired’ groups. Cox regression models were fitted to determine whether there was an association between recorded donor characteristics (endothelial cell density (ECD), age and sex and endothelial graft failure and rejection.

Results

10 838 patients were analysed of whom 1536 (14%) were paired. The unpaired group comprised 1837 (69%) recipients of single corneal donors and 7465 (69%) donors who donated both corneas for another indication. ECD was lower for unpaired single cornea donors (p<0.01). There was no significant difference in endothelial graft failure or rejection between paired and unpaired groups for FED (p=0.37, p=0.99) or PBK (p=0.88, p=0.28) nor for donor ECD, age, sex and paired donation after adjusting for transplant factors (across all models p>0.16 for ECD, p>0.32 for donor age, p>0.14 for sex match and p>0.17 for the donor effect).

Conclusion

The absence of a significant difference in graft outcome for corneal transplants for FED and PBK between paired and unpaired donors may reflect a homogeneous donor pool in the UK.

Influence of time to procurement, incubation and release of organ cultured donor corneas on graft failure after Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE

The aim of the present study was to investigate whether the time from death to procurement, to preservation or the storage time of donor corneas preserved in organ culture influenced the clinical outcome of patients undergoing Descemet stripping automated endothelial keratoplasty (DSAEK) for Fuchs endothelial keratoplasty.

METHODS

We conducted a registry-based study on 776 patients undergoing DSAEK. Data on time from donor death to cornea retrieval (DRT), time from death to preservation (DPT), the preservation time and donor cornea characteristics: age, sex and endothelial cell density (ECD) at the time of release for surgery, were extracted from The Danish Cornea Bank Registry. Data on recipient follow-up were collected from a corneal graft registry. The primary outcome was presence of graft failure within a period from 2 months to 2 years after surgery. Secondary outcomes were DRT, DPT, ECD ≤2300 and gender mismatch between donor and recipient.

RESULTS

Graft failure occurred in 26 patients. The mean preservation time for failed grafts was 34.1 ± 10.0 days (mean ± SD) and 27.3 ± 10.6 days (mean ± SD) for the clear, functional grafts at the 2-year follow-up. A preservation time of >29 days compared with ≤29 days was associated with a lower survival (HR 2.33, 95% CI on 1.06-5.14, p = 0.036) and an increased risk of graft failure (RR 1.53, 95% CI on 1.11-2.10, p = 0.009). For the secondary outcome variables, no difference in the risk of graft failure was observed and did not appear to impact the survival rate of DSAEK patients.

CONCLUSION

Preservation time of donor cornea was associated with graft survival and a prolonged preservation time of more than 4 weeks seemed to lower the 2-year survival.

The importance of donor characteristics, post-mortem time and preservation time for use and efficacy of donated corneas for posterior lamellar keratoplasty

PURPOSE

The aim of this study is to examine whether donor age, death-to-retrieval time (DRT) and death-to-preservation time (DPT) as well as total preservation time affect donor cornea suitability for endothelial keratoplasty (EK) or penetrating keratoplasty (PK).

METHODS

A registry-based study was performed identifying 3248 corneas donated between 2011 and 2017. Data regarding donated corneas were extracted from The Danish Cornea Bank and donor medical records and evaluated for missing information. The primary outcome was whether ECD at preservation (ECD-P) or at release (ECD-R) was >2000 cells/mm² .

RESULTS

Logistic regression for ECD-P showed a significant negative effect of increasing age (OR: 1.07, 95%CI: 1.05;1.08, p < 0.001) on donor suitability. Higher ECD-P had a significant positive effect on graft eligibility (OR: 1.007 95%CI: 1.003;1.010, p < 0.001). No significant effect of donor sex (p = 0.547), DRT (p = 0.289) or DPT (p = 0.102) on donor suitability for EK or PK (Chi-squared test).

CONCLUSION

High donor age and low ECD-P negatively affect the suitability of donor corneas for EK/PK whereas DRT and DPT did not affect graft suitability.

Bioinspired hydrogel surfaces to augment corneal endothelial cell monolayer formation

Corneal endothelial cells (CECs) have limited proliferation ability leading to corneal endothelium (CE) dysfunction and eventually vision loss when cell number decreases below a critical level. Although transplantation is the main treatment method, donor shortage problem is a major bottleneck. The transplantation of in vitro developed endothelial cells with desirable density is a promising idea. Designing cell substrates that mimic the native CE microenvironment is a substantial step to achieve this goal. In the presented study, we prepared polyacrylamide (PA) cell substrates that have a microfabricated topography inspired by the dimensions of CECs. Hydrogel surfaces were prepared via two different designs with small and large patterns. Small patterned hydrogels have physiologically relevant hexagon densities (∼2000 hexagons/mm² ), whereas large patterned hydrogels have sparsely populated hexagons (∼400 hexagons/mm² ). These substrates have similar elastic modulus of native Descemet's membrane (DM; ∼50 kPa) and were modified with Collagen IV (Col IV) to have biochemical content similar to native DM. The behavior of bovine corneal endothelial cells on these substrates was investigated and results show that cell proliferation on small patterned substrates was significantly (p = 0.0004) higher than the large patterned substrates. Small patterned substrates enabled a more densely populated cell monolayer compared to other groups (p = 0.001 vs. flat and p < 0.0001 vs. large patterned substrates). These results suggest that generating bioinspired surface topographies augments the formation of CE monolayers with the desired cell density, addressing the in vitro development of CE layers.

Thickness and Curvature Changes of Human Corneal Grafts in Dextran-Containing Organ Culture Medium Before Keratoplasty

PURPOSE

To determine the changes of corneal thickness and curvature of human corneal grafts in organ culture medium II, containing dextran T500 6%, before keratoplasty.

METHODS

We examined the tomography of 24 corneas from our eye bank transferred from medium I into medium II. Images were repeated hourly during 24 hours using an anterior segment optical coherence tomography. The central corneal thickness (CCT) was measured with the manual measurement tool of the anterior segment optical coherence tomography. The radii of curvature (anterior flat and steep and posterior flat and steep) were measured with a MATLAB self-programmed software for "sterile donor tomography."

RESULTS

The mean CCT (±SD) at baseline (T0) was 727 ± 156 μm. It reached 581 ± 103, 506 ± 84, 472 ± 79, and 456±7 μm after 6, 12, 18, and 24 hours, respectively. After 12 hours, 83% of the final deswelling was achieved. The radii of curvature (±SD) at baseline (T0) were (posterior flat, posterior steep, anterior flat, and anterior steep) 6.6 ± 0.5, 6.2 ± 0.5, 7.7 ± 0.4, and 7.4 ± 0.4 mm, respectively. After 24 hours, the radii of curvature reached 6.8 ± 0.1, 6.6 ± 0.3, 7.6 ± 0.1, and 7.4 ± 0.2 mm, respectively.

CONCLUSIONS

The kinetics of the deswelling process in medium II follow a hyperbolic curve. Considering a CCT of 506 μm at T12, we assume that a time interval of 12 hours in medium II might be enough for clinical purposes. This result might help to keep storage in medium II as short as possible to escape potential toxic effects of dextran in medium II. The radius of curvature does not seem to change within 24 hours for all measured surfaces.

Microbial contamination and tissue procurement location: A conventional operating room is not mandatory. An observational study

BACKGROUND

Standard operating rooms (SOR) are assumed to be the best place to prevent microbial contamination when performing tissue procurement. However, mobilizing an operating room is time and cost consuming if no organ retrieval is performed. In such case, non-operating dedicated rooms (NODR) are usually recommended by European guidelines for tissue harvesting. Performing the tissue retrieval in the Intensive care unit (ICU) when possible might be considered as it allows a faster and simpler procedure.

OBJECTIVE

Our primary objective was to study the relationship between the risk of microbial contamination and the location (ICU, SOR or NODR) of the tissue retrieval in heart-beating and non-heart-beating deceased donors.

MATERIALS AND METHOD

We retrospectively reviewed all deceased donors' files of the local tissue banks of Montpellier and Marseille from January 2007 to December 2014. The primary endpoint was the microbial contamination of the grafts. We built a multivariate regression model and used a GEE (generalized estimating equations) allowing us to take into account the clustered structure of our data.

RESULTS

2535 cases were analyzed involving 1027 donors. The retrieval took place for 1189 in a SOR, for 996 in a hospital mortuary (NODR) and for 350 in an ICU. 285 (11%) microbial contaminations were revealed. The multivariate analysis found that the location in a hospital mortuary was associated with a lower risk of contamination (OR 0.43, 95% CI [0.2-0.91], p = 0.03). A procurement performed in the ICU was not associated with a significant increased risk (OR 0.62, 95% CI [0.26-1.48], p = 0.4).

CONCLUSION

According to our results, performing tissue procurement in dedicated non-sterile rooms could decrease the rate of allograft tissue contamination. This study also suggests that in daily clinical practice, transferring patients from ICU to SOR for tissue procurement could be avoided as it does not lead to less microbial contamination.

Risk Factors for Endothelial Decompensation after Penetrating Keratoplasty and Its Novel Therapeutic Strategies

Purpose

To review the risk factors and pathogenesis of endothelial decompensation after penetrating keratoplasty (PKP) and its novel therapeutic strategies.

Methods

Literature review.

Results

As the major cause of graft failure in PKP, endothelial decompensation of corneal allograft is considered an irreversible decrease in endothelial cell density and endothelial dysfunction. Various risk factors, including donor status and operative and recipient factors, have been found to be associated with this pathological process. Operative factors like graft size and recipient factors such as indications, glaucoma, or glaucoma surgery history are highly associated with the occurrence of endothelial decompensation, while others are still under investigation. Although the mechanism of these risk factors remains unclear, pathogenesis can be summarized as an acute and chronic loss of endothelium, and cell exchange between donor and recipient is at the core of chronic cell loss. Endothelial keratoplasty has been a useful alternative to repeat standard PKP in eyes with failed grafts. Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet's membrane endothelial keratoplasty (DMEK) following failed PKP provide more rapid visual recovery and achieve better rates of graft survival than those of a second PKP.

Conclusions

Any direct or indirect damage to the endothelium could cause the loss, morphological changes, and dysfunction of endothelial cells. Graft size, indications, and recipient glaucoma or glaucoma surgery history are risk factors for endothelial decompensation. DSAEK and DMEK are novel therapeutic strategies for failed PKP grafts and have potential superiorities compared with repeat PKP.

Highly concentrated collagen solutions leading to transparent scaffolds of controlled three-dimensional organizations for corneal epithelial cell colonization

Controlling both organizations and transparency of dense collagen scaffolds.

Easy xeno-free and feeder-free method for isolating and growing limbal stromal and epithelial stem cells of the human cornea

Epithelial and stromal stem cells are required to maintain corneal transparency. The aim of the study was to develop a new method to isolate and grow both corneal stromal (SSC) and epithelial limbal (LSC) stem cells from small human limbal biopsies under culture conditions in accordance with safety requirements mandatory for clinical use in humans. Superficial limbal explants were retrieved from human donor corneo-scleral rims. Human limbal cells were dissociated by digestion with collagenase A, either after epithelial scraping or with no scraping. Isolated cells were cultured with Essential 8 medium (E8), E8 supplemented with EGF (E8+) or Green’s medium with 3T3 feeder-layers. Cells were characterized by immunostaining, RT-qPCR, colony forming efficiency, sphere formation, population doubling, second harmonic generation microscopy and differentiation potentials. LSC were obtained from unscraped explants in E8, E8+ and Green’s media and were characterized by colony formation and expression of PAX6, ΔNP63α, Bmi1, ABCG2, SOX9, CK14, CK15 and vimentin, with a few cells positive for CK3. LSC underwent 28 population doublings still forming colonies. SSC were obtained from both scraped and unscraped explants in E8 and E8+ media and were characterized by sphere formation, expression of PAX6, SOX2, BMI1, NESTIN, ABCG2, KERATOCAN, VIMENTIN, SOX9, SOX10 and HNK1, production of collagen fibrils and differentiation into keratocytes, fibroblasts, myofibroblasts, neurons, adipocytes, chondrocytes and osteocytes. SSC underwent 48 population doublings still forming spheres, Thus, this new method allows both SSC and LSC to be isolated from small superficial limbal biopsies and to be primary cultured in feeder-free and xeno-free conditions, which will be useful for clinical purposes.

Improving the success rate of human corneal endothelial cell cultures from single donor corneas with stabilization medium

Main objective of this study was to improve the success rate of human corneal endothelial cell (hCEC) cultures from single donor corneas. We could show that the use of stabilization medium prior to cell isolation may have a positive effect on the success rate of hCEC cultures from single research-grade donor corneas by allowing growth of otherwise possibly not successful cultures and by improving their proliferative rate. hCEC were obtained from corneo-scleral rims of 7 discarded human research-grade cornea pairs. The Descemet membrane-endothelium (DM-EC) sheets of each pair were assigned to 2 experimental conditions: (1) immediate cell isolation after peeling, and (2) storage of the DM-EC sheet in a growth factor-depleted culture medium (i.e. stabilization medium) for up to 6 days prior to cell isolation. hCEC isolated by enzymatic digestion were then induced to proliferate on pre-coated culture plates. The success rate of primary cultures established from single donor corneas were higher for DM-EC sheets kept in stabilization medium before cell isolation. All cultures (7/7) initiated from stabilized DM-EC sheets were able to proliferate up to the third passage, while only 4 out of 7 cultures initiated from freshly peeled DM-EC sheets reached the third passage. In addition, for the 4 successful paired cultures we observed a faster growth rate if the DM-EC sheet was pre-stabilized prior to cell isolation (13.8 ± 1.8 vs 18.5 ± 1.5 days, P < 0.05). Expression of the phenotypical markers Na⁺/K⁺-ATPase and ZO-1 could be shown for the stabilized cultures that successfully proliferated up to the third passage.

New parameters in assessment of human donor corneal stroma

PURPOSE

To provide quantitative parameters for assessment of human donor corneal stroma by imaging stromal features of diseased and normal human corneas with full-field optical coherence microscopy (FFOCM), using confocal microscopy (CM) and histology as reference techniques.

METHODS

Bowman's layer (BL) thickness and keratocyte density were assessed ex vivo in 23 human donor corneas and 27 human pathological corneas (keratoconus and other corneal disorders) with FFOCM, CM and histology. Stromal backscattering was assessed with FFOCM. Additionally, 10 normal human corneas were assessed in vivo with CM.

RESULTS

In FFOCM, the logarithm of the normalized stromal reflectivity was a linear function of stromal depth (R²  = 0.95) in human donor corneas. Compared with keratoconus corneas, human donor corneas featured higher BL thickness (p = 0.0014) with lower coefficient of variation (BL-COV; p = 0.0002), and linear logarithmic stromal reflectivity with depth (higher R² , p = 0.0001). Compared with other corneal disorders, human donor corneas featured lower BL-COV (p = 0.012) and higher R² (p = 0.0001). Using the 95% confidence limits of the human donor cornea group, BL thickness < 6.5 μm (sensitivity, 57%; specificity, 100%), BL-COV > 18.6% (79%; 100%) and R²  < 0.94 (93%; 71%) were revealed as indictors of abnormal cornea. In CM, keratocyte density decreased with stromal depth (r = -0.56). The mean overall keratocyte density (cells/mm² ) was 205 in human donor corneas, 244 in keratoconus, 176 in other corneal disorders and 386 in normal corneas.

CONCLUSION

Full-field optical coherence microscopy (FFOCM) provides precise and reliable parameters for non-invasive assessment of human donor corneal stroma during storage, enabling detection of stromal disorders that could impair the results of keratoplasty.

Factors Affecting Treatment Outcome of Graft Infection Following Penetrating Keratoplasty

Purpose

To evaluate the factors affecting treatment outcome of graft infection following penetrating keratoplasty (PKP).

Methods

In this retrospective study, 28 patients who underwent PKP between January 2005 and January 2013 and who were diagnosed with graft infection were classified into a treatment success group or a treatment failure group. Demographic and clinical characteristics, as well as the results of the microbiologic investigation, were analyzed and compared. A subsequent binary logistic regression analysis was performed to identify the prognostic factors affecting treatment outcome.

Results

Graft infection occurred at a mean of 38.29 ± 36.16 months (range, 1 to 96 months) after PKP. Seventeen patients developed bacterial keratitis, and 11 patients developed fungal keratitis. Overall, of the 28 patients, nine (32.1%) were classified in the treatment failure group. Multivariate analysis identified pre-existing graft failure (p = 0.019), interval longer than 72 hours between donor death and PKP (p = 0.010), and fungal infection (p = 0.026) as significant risk factors for treatment failure.

Conclusions

Pre-existing graft failure, extended interval between donor death and PKP, and fungal infection were important risk factors for treatment failure of graft infection following PKP.

Development of human corneal epithelium on organized fibrillated transparent collagen matrices synthesized at high concentration

Several diseases can lead to opacification of cornea requiring transplantation of donor tissue to restore vision. In this context, transparent collagen I fibrillated matrices have been synthesized at 15, 30, 60 and 90 mg/mL. The matrices were evaluated for fibril organizations, transparency, mechanical properties and ability to support corneal epithelial cell culture. The best results were obtained with 90 mg/mL scaffolds. At this concentration, the fibril organization presented some similarities to that found in corneal stroma. Matrices had a mean Young's modulus of 570 kPa and acellular scaffolds had a transparency of 87% in the 380-780 nm wavelength range. Human corneal epithelial cells successfully colonized the surface of the scaffolds and generated an epithelium with characteristics of corneal epithelial cells (i.e. expression of cytokeratin 3 and presence of desmosomes) and maintenance of stemness during culture (i.e. expression of ΔNp63α and formation of holoclones in colony formation assay). Presence of cultured epithelium on the matrices was associated with increased transparency (89%).

[Influence of surgical technique on graft and endothelial survival in endothelial keratoplasty]

PURPOSE

To report survival of the graft and its endothelium after Descemet Stripping Endothelial Keratoplasty (DSEK) in a series of consecutive cases with no exclusion of cases corresponding to the learning curve and to analyze the influence of surgical techniques on survival.

PATIENTS AND METHODS

This prospective observational study includes 170 consecutive DSEK's performed between 2006 and 2013. The main outcome criteria were graft survival and survival of the donor corneal endothelium as assessed by specular microscopy. The following parameters were analyzed: preoperative diagnosis, lens status, surgical techniques, and graft thickness.

RESULTS

Graft survival was 91.7% at 1 year and 71.5% at 3 years. Graft survival was significantly associated with surgical technique (P=0.04). The best graft survival was achieved with scleral incision combined with graft insertion with the Endosaver® device (dedicated DSEK injector). Graft survival decreased with graft thickness (P<0.001). One-year endothelial cell density was significantly associated with surgical technique (P=0.003). Early 1-year endothelial cell loss was 42.0% for the scleral incision/Endosaver® group, 48.7% for the corneal incision/Endosaver® group, 49.4% for the corneal incision/Busin guide group, 66.0% for the corneal incision/IOL injector group, and 66.7% for the scleral incision/forceps group (P=0.002).

CONCLUSION

The success rate of DSEK is close to that of penetrating keratoplasty. The use of a DSEK-dedicated injector results in higher survival of the graft and its endothelium. The use of ultrathin grafts also appears to represent significant progress.

Eye-bank preparation of endothelial tissue

PURPOSE OF REVIEW

Eye-bank preparation of endothelial tissue for keratoplasty continues to evolve. Although eye-bank personnel have become comfortable and competent at Descemet's stripping automated endothelial keratoplasty (DSAEK), tissue preparation and tissue transport, optimization of preparation methods continues. Surgeons and eye-bank personnel should be up to date on the research in the field. As surgeons transit to Descemet's membrane endothelial keratoplasty (DMEK), eye banks have risen to the challenge of preparing tissue. Eye banks are refining their DMEK preparation and transport techniques.

RECENT FINDINGS

This article covers refinements to DSAEK tissue preparation, innovations to prepare DMEK tissue, and nuances to improve donor cornea tissue quality.

SUMMARY

As eye bank-supplied corneal tissue is the main source of tissue for many corneal surgeons, it is critical to stay informed about tissue handling and preparation. Ultimately, the surgeon is responsible for the transplantation, so involvement of clinicians in eye-banking practices and advocacy for pursuing meaningful research in this area will benefit clinical patient outcomes.

Micro- and nanotopography with extracellular matrix coating modulate human corneal endothelial cell behavior

The human corneal endothelium plays an important role in maintaining corneal transparency. Human corneal endothelial cells have limited regenerative capability in vivo. Consequently, endothelial dysfunction can occur following corneal endothelial trauma or inherited diseases. To restore endothelial function, corneal transplantation is needed. However, there is a worldwide shortage of donor corneas, motivating the development of a tissue-engineered graft alternative using cultivated endothelial cells. To induce in vitro cell proliferation, much effort has been made to improve culture conditions and to mimic the native extracellular microenvironment. We incorporated topographical and biochemical cues in our in vitro culture of human corneal endothelial cell line B4G12 (HCEC-B4G12) and hypothesized that manipulation of the extracellular environment can modulate cell proliferation, morphometry and phenotype. The topographies tested were nanopillars, microwells and micropillars on polydimethylsiloxane, while the biochemical factors were extracellular matrix protein coatings of fibronectin-collagen I (FC), FNC® coating mix (FNC) and laminin-chondroitin sulfate (LC). Cellular morphometry, Na(+)/K(+)-ATPase and zona occludens 1 (ZO-1) gene and protein expression were analyzed 3days after cells had formed a confluent monolayer. The cell circularity on all patterns and coatings was above 0.78. On all coatings, cell area was the lowest on micropillars. The coefficient of variation (CV) of the cell area was the lowest on nanopillars with an LC coating. With an FC coating, micropillars induced a better cellular outcome as the cells had the greatest circularity, smallest cell area and highest Na(+)/K(+)-ATPase and ZO-1 gene and protein expression. With the LC coating, HCECs grown on nanopillars resulted in the lowest CV of the cell area and the highest ZO-1 gene expression. Thus, HCEC-B4G12 morphometry and phenotype can be improved using different topographical and biochemical cues.

Donor tissue selection for anterior lamellar keratoplasty

PURPOSE

To assess the influence of donor characteristics on the outcome of anterior lamellar keratoplasty (ALK) and to evaluate whether corneal donor tissue considered unsuitable for penetrating or posterior lamellar keratoplasty due to poor endothelial condition may be safely used for ALK.

METHODS

Institutional setting. One hundred sixty-six consecutive ALK (166 patients) performed for optical indication in eyes with corneal diseases not involving the corneal endothelium. The main outcome measures were graft survival, early (0-12 months postoperatively) and late (after 12 months) annual endothelial cell loss, and postoperative logarithm of the minimum angle of resolution visual acuity.

RESULTS

The average and extreme values of donor tissue characteristics were: donor age, 70.6 years (range, 28-88 years); organ culture time, 20.9 days (range, 12-35 days); graft endothelial cell density before transplantation, 2047 cells per millimeters (range, 100-3300 cells/mm2); and deswelling time, 2.0 days (range, 1-4 days). The average follow-up time of patients was 48.1 ± 24.8 months (mean ± SD). None of the donor characteristics significantly influenced graft survival or postoperative endothelial cell loss (early and late phase). Donor age >80 years was associated with lower postoperative visual acuity at all postoperative points in time (P < 0.05). At 3 years, the mean logarithm of the minimum angle of resolution visual acuity was 0.44 (20/55) for grafts from donors older than 80 years and 0.25 (20/35) for younger donors. This result was shown to be significant both in univariate and in multivariate analysis.

CONCLUSIONS

Grafts from elderly donors should be discarded before ALK. Conversely, donor tissue with poor endothelial cell density (<2000 cells/mm2) is suitable for ALK.

Kinetics of expansion of human limbal epithelial progenitor cells in primary culture of explants without feeders

The aims of this study were to determine whether human limbal explant cultures without feeder cells result in expansion of epithelial progenitors and to estimate the optimal expansion time for progenitor cells. Limbal explants from ten human corneas were cultured for 7, 9, 11, 14, 18, and 21 days. Limbal explants from two corneas were enzymatically dissociated or directly cultured for 14 days. Progenitor cells were characterized by their ability to form colonies, by immunocytochemistry, and by quantitative real-time polymerase chain reaction. Colonies were identified after 9, 11, 14, and 18 days of culture, but not after 21 days. The number of colonies per explant was significantly higher after 14 days than after 9 and 21 days. The mean percentage of seeded cells giving rise to clones was 4.03% after 14 days of culture and 0.36% for non-cultured dissociated limbal epithelial cells. The number of cells giving rise to clones per cornea significantly increased from an average of 2275 for non-cultured cells to 24266 for cells cultured for 14 days. Immunocytochemical analysis detected positive staining for cytokeratin (CK) 3, CK5/6/8/10/13/18, CK19, vimentin, p63, and p63α, in both cultures and clones. CK3 expression increased significantly with culture time. Transcript expression was observed for CK3, CK19, vimentin, and Delta N p63α at each culture time point, both in cultures and clones. The optimal culture time for limbal explants in cholera toxin-free Green medium without feeder cells was 14 days leading to the expansion of progenitors.

Long-term rejection incidence and reversibility after penetrating and lamellar keratoplasty

PURPOSE

To identify risk factors for corneal graft rejection and rejection irreversibility.

DESIGN

Retrospective cohort study.

METHODS

setting: Institutional. patients: A total of 1438 consecutive eyes of 1438 patients who underwent corneal transplantation for optical indication at the Centre Hospitalier National d'Ophtalmologie des XV-XX, Paris, France, between December 1992 and December 2010 were studied. Surgical technique was penetrating keratoplasty (PK) in 1209 cases, anterior lamellar keratoplasty (ALK) in 165 cases, and Descemet stripping with endothelial keratoplasty in 64 cases. main outcome measures: Cumulative incidence of rejection episodes and rejection irreversibility rate.

RESULTS

A total of 299 cases of rejection episodes were identified, of which 145 (48.5%) were irreversible after treatment. In multivariate analysis, the cumulative incidence of rejection episodes was influenced by recipient age (P = .00002), recipient rejection risk (P = .0003), lens status (P = .00003), and surgical group (P = .035). A higher incidence of rejection episodes was observed in young patients (<20 years) and patients aged from 41 to 50, high-risk recipients, aphakic eyes and eyes with anterior chamber intraocular lens, and eyes with PK (compared with eyes with ALK). Rejection episodes were more likely to be irreversible for high-risk recipients (P = .02), for eyes with preoperative hypertony (P = .009), and for eyes with poor visual acuity at presentation (P = .002).

CONCLUSIONS

Recipient rejection risk and surgical group are the main risk factors for rejection as they both influence the incidence of rejection and the reversibility rate. Recipient age and lens status are predictive factors for the occurrence of rejection. Preoperative hypertony is a predictive factor for rejection irreversibility.

Effects of isoproterenol and cholera toxin on human limbal epithelial cell cultures

PURPOSE

Cholera toxin and isoproterenol (β-adrenergic receptor agonist) are largely used to enhance cell proliferation. The aim of the study was to assess the effects of cholera toxin and isoproterenol on growth and differentiation of cells cultured from human superficial limbal explants.

METHODS

Limbal epithelial cells were cultured from superficial limbal explantsin basal medium either supplemented with cholera toxin or isoproterenol for 3 weeks. Growth kinetics and morphometry were studied by light and confocal microscopy. Progenitor and differentiated epithelial cell markers were studied by immunocytochemistry, flow cytometry, Colony Formation Assay, and reverse transcription and polymerase chain reaction.

RESULTS

Cell proliferation was significantly higher with 0.5 µg/ml (p = 0.049), 1 µg/ml (p = 0.005), and 2 µg/ml (p = 0.008) isoproterenol whereas, cholera toxin and 4 µg/ml isoproterenol did not significantly increase cell proliferation. Multilayered epithelial cell sheets were obtained in all culture conditions. Addition of isoproterenol resulted in smaller cell size (p < 0.05) 14 days after cells were cultured, whereas cholera toxin had no effects. Strong expression of cytokeratins 3 and 4/5/6/8/10/13/18 and lower expression of cytokeratin 19, vimentin, and Delta N p63α were observed after 3 weeks of culture with no significant differences in the percentage of positive cells according to culture medium. Colony-forming efficiencies were observed after 2 weeks in all culture condition but not after 3 weeks.

CONCLUSION

Isoproterenol was more efficient than cholera toxin for enhancing cell proliferation and resulted in smaller cell size. It appears to be useful and safe for growing human limbal epithelial progenitors from limbal explants with no feeders before transplantation to patients with limbal deficiency.

Long-term results of deep anterior lamellar versus penetrating keratoplasty

OBJECTIVE

To compare deep anterior lamellar keratoplasty (DALK) with penetrating keratoplasty (PK) in eyes with corneal diseases not involving the corneal endothelium (keratoconus, scars after infectious keratitis, stromal dystrophies, and trauma).

DESIGN

Retrospective, comparative case series.

PARTICIPANTS

One hundred forty-two consecutive DALK (DALK group; big-bubble technique or manual lamellar dissection using a slitlamp) and 142 matched PK (PK group).

METHODS

Three models were used to describe the postoperative outcomes of the endothelial cell density. A joint regression model was used to predict long-term graft survival. Visual acuity, ultrasound pachymetry, specular microscopy, and optical coherence tomography (OCT) findings were recorded.

MAIN OUTCOME MEASURES

Postoperative endothelial cell loss and long-term predicted graft survival.

RESULTS

The average 5-year postoperative endothelial cell loss was -22.3% in the DALK group and -50.1% in the PK group (P<0.0001). The early- and late-phase annual rates of endothelial cell loss were -8.3% and -3.9% per year, respectively, in the DALK group and -15.2% and -7.8% per year in the PK group (P<0.001; biphasic linear model). The median predicted graft survival was 49.0 years in the DALK group and 17.3 years in the PK group (P<0.0001). The average visual acuity was lower in the manual dissection subgroup compared with the PK group (average difference, 1.0 to 1.8 line) and with the big-bubble subgroup (average difference, 2.2 to 2.5 lines). The average central corneal thickness at 12 months was 536 μm in the PK group, 523 μm in the big-bubble subgroup, and 562 μm in the manual dissection subgroup (P<0.001). The average thickness of the residual recipient stroma measured by OCT was 87±26 μm in the manual dissection subgroup. No correlation was found between this figure and logarithm of the minimal angle of resolution at any postoperative time point (P>0.05).

CONCLUSIONS

Long-term, model-predicted graft survival and endothelial densities are higher after DALK than after PK. The big-bubble technique gives better results than manual dissection and PK. Compared with PK, manual dissection provides higher survival of both the corneal endothelium and graft, but lower visual acuity.

Donor tissue culture conditions and outcome after descemet membrane endothelial keratoplasty

PURPOSE

To investigate the effect of culture conditions of donor tissue on functional outcome after Descemet membrane endothelial keratoplasty.

DESIGN

Retrospective, single-center, consecutive case series.

METHODS

Descemet membrane endothelial keratoplasty was performed routinely in 82 eyes of 82 consecutive patients using corneal donor tissue prestored in either short-term culture (Optisol-GS; Bausch & Lomb) at 4 C (group A; n = 37) or organ culture (Dulbecco Modified Eagle Medium [Biochrom]; CorneaMax Medium [Eurobio]) at 34 C (group B; n = 45) in a randomized fashion. Main outcome measures included the number of air injections necessary for graft attachment as well as best-corrected visual acuity (in logarithm of the minimal angle of resolution [logMAR] units), central corneal thickness, and endothelial cell density at 1, 3, and 6 months after surgery.

RESULTS

Best-corrected visual acuity increased from 0.69 ± 0.53 logMAR and 0.67 ± 0.31 logMAR before surgery to 0.33 ± 0.21 logMAR and 0.28 ± 0.18 logMAR after 1 month (P < .05), to 0.24 ± 0.16 logMAR and 0.18 ± 0.16 logMAR after 3 months (P < .05), and to 0.18 ± 0.12 logMAR and 0.15 ± 0.10 logMAR after 6 months (n.s.) in groups A and B, respectively. Endothelial cell density decreased from 2647 ± 236 cells/mm(2) and 2515 ± 249 cells/mm(2) before surgery to 1499 ± 277 cells/mm(2) and 1526 ± 205 cells/mm(2) after 1 month (P < .05), to 1441 ± 213 cells/mm(2) and 1443 ± 316 cells/mm(2) after 3 months (n.s.), and to 1587 ± 366 cells/mm(2) and 1457 ± 285 cells/mm(2) after 6 months (n.s.) in groups A and B, respectively. Central corneal thickness declined from 664 ± 89 and 662 ± 107 μm before surgery to 529 ± 92 μm and 517 ± 62 μm after 1 month (P < .05), to 511 ± 46 μm and 510 ± 46 μm after 3 months (P < .05), and to 529 ± 68 μm and 507 ± 50 μm after 6 months (n.s.) in groups A and B, respectively. Best-corrected visual acuity, endothelial cell density, and central corneal thickness values showed no significant differences between both groups at any time point after surgery. However, a significantly higher total number of air injections was necessary in group A (n = 34) compared with group B (n = 26) to obtain graft attachment (P < .05).

CONCLUSIONS

These findings suggest that donor tissue culture conditions have no significant effect on functional outcome, but may influence graft adhesion and rebubbling rate after Descemet membrane endothelial keratoplasty surgery.

Human epithelial cell cultures from superficial limbal explants

PURPOSE

To study the kinetics of growth and the phenotype of cells cultured from human limbal explants in a cholera toxin-free medium with no feeder cell layer.

METHODS

Human organ-cultured corneas were used to prepare limbal explants (full-thickness and superficial limbal explants) and corneal stromal explants. Cell growth kinetics and phenotypes were assessed by cultivating explants in cholera toxin-free Green medium. Epithelial and progenitor cell markers were assessed by immunocytochemistry, flow cytometry, and Reverse Transcription and Polymerase Chain Reaction (RT-PCR).

RESULTS

The successful epithelial cell growth rates from full thickness limbal explant and superficial limbal explant tissues were 41 and 86%, respectively (p=0.0001). The mean cell area and the percentage of small cells in superficial and full-thickness explant cultures were, respectively, 317 µm(2) and 429 µm(2), and 8.9% and 1.7% (p<0.001). The percentage of positive cells in superficial and full-thickness limbal explant cultures as assessed by immunocytochemistry were the following: broad spectrum cytokeratins (cytokeratins 4, 5, 6, 8, 10, 13, and 18 [MNF116]), 82%/37% (p=0.01); cytokeratin 3 (CK3), 74%/25% (p=0.009); cytokeratin 19 (CK19), 46%/25% (p=0.19); vimentin, 56%/53% (p=0.48); delta N p63α, 54%/0% (p<0.001); and ABCG2, 5%/0% (p=0.1). Flow cytometry showed a higher percentage of small cells, a higher percentage of MNF116+ cells, and stronger expression of progenitor-associated markers in superficial than in full-thickness explant cultures. For superficial limbal explant cultures, analysis of the expression profiles for various mRNAs at the end of 21 days of culture showed high levels of expression of the mRNAs encoding CK3, vimentin, and CK19. The expression of mRNA of delta N p63α and ABCG2 was weaker. Cultures obtained from full-thickness limbal explants featured no expression of mRNA of CK19, delta N p63α, and ABCG2, whereas mRNAs encoding CK3 and vimentin were detected. Human corneal stromal explants cultured with the same medium featured late cell growth, large mean cell area (2,529 µm(2)), no expression of cytokeratins, delta N p63α, and ABCG2, and high expression of vimentin.

CONCLUSIONS

Superficial limbal explants appear to be superior to full-thickness limbal explants for growing human limbal epithelial cells. Preparation of explants using surgical facilities (i.e., operating microscope and microsurgical blades) led to a dramatic increase in the percentage of successful cultures, higher epithelial cell growth, decreased fibroblast contamination, and better preservation of limbal epithelial progenitors.

Influencing factors on the suitability of organ-cultured corneas

PURPOSE

To determine the factors related to donor and tissue retrieval, which influence the suitability of organ-cultured corneas for transplantation.

PATIENTS AND METHODS

We retrospectively analysed 2596 donor corneas. Polytomic logistic regression analysis was used to assess the influence of various factors (that is, donor age, cause of death, death-to-tissue retrieval time, tissue retrieval-to-reception time, and tissue retrieval method) on the suitability of grafts for transplantation. Positive predictive values (PPVs) were computed.

RESULTS

Forty-three percent (1118/2596) of corneas were discarded. The leading cause for discarding corneas was poor endothelial quality (21.5%). Corneas from donors older than 80 years were more likely to be discarded because of endothelial insufficiency (OR=2.37, P=0.001). Longer time between death and tissue retrieval was associated with increased risk of positive serology (OR=1.43, P=0.02). Increased time between tissue retrieval and reception was associated with increased risk of contamination (OR=1.57, P=0.03). PPV increased from 38.5% for corneas retrieved from donors older than 80 years featuring a death-to-tissue retrieval time of more than 6 h and a tissue retrieval-to-reception time of more than 24 h to 64.7% for corneas retrieved from donors younger than 80 years featuring a death-to tissue retrieval time shorter than 6 h and a tissue retrieval-to-reception time shorter than 24 h.

CONCLUSION

The percentage of discarded corneas can be reduced by including donors aged 80 years or less, using a time from donor's death to tissue retrieval shorter than 6 h, and a tissue retrieval-to-reception time shorter than 24 h.

Predicted long-term outcome of corneal transplantation

OBJECTIVE

To analyze graft survival and the outcome of the corneal endothelium after corneal transplantation in a single model to predict the long-term prognosis of these grafts.

DESIGN

Cohort study. Data were recorded prospectively and then analyzed retrospectively.

PARTICIPANTS

One thousand one hundred forty-four consecutive eyes of 1144 patients who underwent corneal transplantation between 1992 and 2006.

INTERVENTIONS

Penetrating keratoplasty and deep anterior lamellar keratoplasty.

MAIN OUTCOME MEASURES

Slit-lamp examination and wide-field specular microscopy results. A joint analysis of endothelial cell loss and time to graft failure was undertaken. From midterm simultaneous analysis of graft survival and endothelial cell loss, long-term graft survival was predicted.

RESULTS

The observed 5- and 10-year graft survival estimates were, respectively, 74% and 64%. The average endothelial cell density (cell loss) was 2270 cells/mm(2) before surgery, 1058 cells/mm(2) (-53%) during the sixth postoperative year, and 865 cells/mm(2) (-61%) during the 10th postoperative year. Overall, the predicted graft survival estimate was 27% at 20 years and 2% at 30 years. Both observed and predicted graft survival were higher in patients who had undergone lamellar keratoplasty than in patients who had undergone penetrating keratoplasty and had normal recipient endothelium and higher in patients who had undergone penetrating keratoplasty and had normal recipient endothelium than in patients who had undergone penetrating keratoplasty and had impaired recipient endothelium.

CONCLUSIONS

For corneal diseases involving the endothelium, penetrating keratoplasty seems to be a good therapeutic approach in elderly patients because the graft life-span may be similar to the patient life expectancy. Conversely, for younger patients, penetrating keratoplasty is only a midterm therapeutic approach. For corneal diseases not involving the endothelium, deep anterior lamellar keratoplasty seems to be a promising therapeutic approach with higher long-term expected survival.

Optimizing the deswelling process of organ-cultured corneas

PURPOSE

During deswelling of organ-cultured human corneas, endothelial cell loss occurs. Therefore, it is necessary to minimize the deswelling time and achieving an optimal central corneal thickness (CCT) of approximately 550 microm at the same time. We investigated the minimal deswelling time necessary and analyzed endothelial cell loss.

METHODS

Fifty-eight human corneas were stored between 13 and 81 days in organ culture. CCT was measured by optical coherence tomography. Measurements were performed before preparation, during culturing, before deswelling, and after varying deswelling periods (1-72 hours) using 5% dextran. Additionally, vital staining was performed in 6 human corneas to assess endothelial cell loss between 24 and 30 hours of deswelling. To evaluate absolute cell loss, endothelial cells were counted on human corneal pairs after 24 and 30 hours of deswelling.

RESULTS

After organ culture, mean CCT was 1194 microm. After 24 hours of deswelling in dextran-containing medium, mean CCT was 600 microm, whereas after 30 hours, mean CCT was 510 microm and hardly any corneas showed a CCT of more than 550 microm. Almost no further decrease in CCT was observed thereafter. No factors could be identified predicting the necessary deswelling time; however, paired corneas showed significant correlation of deswelling characteristics. We did not see any differences in endothelial cell loss 24 and 30 hours of deswelling or the ratio of living to dead endothelial cell counts.

CONCLUSIONS

Deswelling for 24 hours does not provide an optimal corneal thickness. Because endothelial cell loss does not increase between 24 and 30 hours of deswelling, a period of 30 hours is more suitable for obtaining sufficient corneal thickness.

The influence of donor and recipient factors in allograft rejection of the human cornea

The health of the corneal endothelium is essential in maintaining the clarity of the transplanted human cornea. Immune-mediated endothelial rejection is a complex series of events, which may culminate in the decompensation of the donor button. It is the commonest instigator of failure in penetrating corneal transplantation.

METHODS

This retrospective case note review of 203 penetrating keratoplasties with adequate follow-up data during a 5-year study period from 1 January 2000 to 31 December 2003 at Manchester Royal Eye Hospital, were used for analysis.

RESULTS

Forty-three of the 203 donor grafts underwent at least one single episode of immune-mediated endothelial rejection, an incidence of 21% over a 5-year follow-up. Recipient's age was inversely associated with the risk of rejection. The average age for the cohort of 58.7 years and average age for rejecting patients of 47.6 years were strongly significantly different (P=0.009). Rejection in keratoconic patients accounted for 30% of cases. Death to enucleation time (P=0.03) was also associated with an increased risk of rejection.

CONCLUSION

Although penetrating keratoplasty is an effective long-term treatment option for improving visual function, the endothelial rejection rate in our study was 21% over a mean follow-up of over 5 years. Host vascularisation, regrafts, younger recipient age group, and donor factors were found to be significantly associated with a risk of rejection. Rejection in keratoconic recipients was more common than expected.

Regeneration with proliferation of the endothelium of cultured human donor corneas with extended postmortem time

PURPOSE

To examine the endothelium of donor corneas with extended postmortem time for survival and reparative mechanisms in an eye bank organ culture storage system.

METHODS

We obtained 14 pairs of donor corneas with a postmortem time ranging from 29 to 163 hours. One cornea of a pair was immediately fixed for the study of structural changes postmortem and to serve as a control. The second was stored in organ culture for 3 days and thereafter fixed to be studied for reparative processes. Examination was done with light microscopy and scanning electron microscopy. Immunohistochemical staining with antibodies against proliferating cell nuclear antigen, Ki-67, and n-cadherin was performed to examine for cell proliferation and to characterize the cells.

RESULTS

The control corneas showed increasing endothelial cell damage with increasing postmortem time. After 5-7 days postmortem, most cells were structurally damaged. After 3 days in organ culture, all corneas acquired an endothelial covering of the posterior surface, with cells, suggesting proliferation in both scanning preparations and in cross-sections. Positive endothelial cell staining with proliferating cell nuclear antigen was found in all cultured corneas. Ki-67 staining of the endothelium was found in 9 of the cultured corneas.

CONCLUSIONS

The study showed survival of the corneal endothelium up to 7 days postmortem, and accordingly, the potential clinical use of donor corneas with extended postmortem time. Our results furthermore suggest that repair of the endothelium in donor corneas during organ culture storage occurs also by proliferation and not only by migration and enlargement of existing cells. If we uncover the mechanisms regulating cell proliferation in corneal endothelium, it should be possible to develop better storage methods of corneal transplants to improve quality and supply.

Late Changes in Refraction, Pachymetry, Visual Acuity, and Corneal Topography After Penetrating Keratoplasty

PURPOSE

To analyze the late changes in refraction, corneal topography, and pachymetry after penetrating keratoplasty.

METHODS

We have retrospectively analyzed data of 64 eyes of 56 patients with a clear corneal graft and no other ocular diseases. The eyes were examined soon and several years after all sutures were removed, at 19.5 +/- 3.1 months and 76.8 +/- 25.2 months, respectively, after keratoplasty. All eyes were examined using the EyeSys 2000 videokeratograph and the Tomey SP2000 ultrasonic pachymeter. Corneal surface regularity was studied using the indices provided by the Holladay Diagnostic Summary (ie, asphericity coefficient Q; corneal uniformity index CU; predicted corneal acuity PCA). Irregular astigmatism was quantified using semimeridian data from videokeratographs (refractive power symmetry index).

RESULTS

Visual acuity increased by an average of 0.35 +/- 0.93 lines (P = 0.002) between the 2 examinations, whereas no significant changes in refraction and videokeratoscopy (ie, power, indices, and irregular astigmatism) were observed (P > or = 0.08). Central corneal thickness significantly increased from 542 +/- 31 microm to 572 +/- 38 microm (P < 0.001). Change in BSCVA did not significantly correlate with the change in refraction, in topographic indices, or in irregular astigmatism (rs < or = 0.13; P > or = 0.16).

CONCLUSION

Late after penetrating keratoplasty, best corrected visual acuity shows a small but statistically significant improvement, whereas refraction and corneal surface regularity are stable. This late improvement in visual acuity is not explained by current techniques.

Efficiency of blood culture bottles for the fungal sterility testing of corneal organ culture media

BACKGROUND/AIM

The consequences of fungal contamination of an organ cultured cornea, though exceptional, are often disastrous for the recipient. Consequently, eye banks often quarantine corneas for 10 days or more before passing them for grafting. This period, though detrimental to the endothelial cell density of the delivered cornea, is necessary to detect contamination using conventional microbiological methods. The authors previously validated the use of a pair of aerobic and anaerobic blood bottles for sensitive and rapid detection of bacteria. To allow a short quarantine period, it remained only to optimise detection of fungi. The authors aimed to compare sensitivity and rapidity of fungal contamination detection by three methods: blood bottles, Sabouraud, and daily visual inspection of the organ culture medium.

METHODS

Four inocula (10(6), 10(4), 10(2), 10 colony forming unit (CFU) per ml) of 11 fungi (Candida albicans, C tropicalis, C glabrata, Saccharomyces cerevisiae, Rhodotorula rubra, Cryptococcus neoformans, Fusarium oxysporum, Aspergillus niger, A fumigatus, A flavus, Acremonium falciforme) were inoculated in a commercial organ culture medium containing a coloured pH indicator (CorneaMax, Eurobio, Les Ulis, France). The real live fungal inoculum was verified immediately after inoculation. After 48 hours at 31 degrees C, samples of the contaminated media were inoculated in three blood bottles: Bactec Aerobic/F, Bactec Mycosis IC/F, and Bactec Myco/F Lytic (Becton Dickinson, Le Pont de Claix, France), then placed in a Bactec 9240 rocking automat, and in four Sabouraud media (solid and liquid, 28 degrees C and 37 degrees C) with daily observation. Contaminated organ culture media were also checked daily for any change in turbidity and/or colour. Experiments were performed in triplicate.

RESULTS

Mycosis IC/F and Myco/F Lytic bottles were neither faster nor more sensitive than the aerobic bottle. The three methods were positive for all inocula, even the lowest (viable inoculum below 10 CFU/ml for each fungus). Contamination was detected within 24 hours by the aerobic bottles in 91% (40/44), by Sabouraud in 98% (43/44) (no significant difference) and by visual inspection in 66% of cases (29/44) (p<0.001 with the two others). Maximum times to detection were 46, 48 and 72 hours respectively.

CONCLUSION

This study further counters the preconception that fungal contamination is hard to detect in corneal organ culture media. This study is the last step in validating the use of a pair of blood bottles for the sterility testing of organ culture media, this time for fungi. Their use should make it possible to shorten microbiological quarantine and thus deliver corneas with higher endothelial cell density, without increasing the risk of recipient contamination.

Improvement of graft prognosis in penetrating normal-risk keratoplasty by HLA class I and II matching

BACKGROUND

Owing to contradictory results, HLA matching in penetrating keratoplasty still is equivocal. Different surgical techniques in multicentre studies, missing risk differentiation in high-risk situations, and faulty HLA typing can be identified as main reasons for these contradictory results. In this monocentre study, the value of HLA class I and II matching (A, B, DR loci) was examined in a homogeneous group of 418 normal-risk keratoplasty patients using serological typing techniques for HLA class I and immunogenetic typing techniques for class II.

METHODS

Penetrating normal-risk keratoplasty was performed in two groups of patients (group I with 0-2, group II with 3-6 mismatches in the A/B/DR loci). All surgery was carried out by three experienced surgeons according to a standardized scheme. Furthermore, postoperative therapy and controls were standardized. There were no statistically significant differences between the two study groups with regard to the number of ABO or H-Y compatibilities, patient age, patient gender, ratio of previous intraocular surgery, ratio of triple procedures, indication for surgery, follow-up period, donor age, donor gender, post-mortem time of the graft, and endothelial cell density of the graft at the end of organ culture. All HLA typing was performed in a quality-controlled laboratory, serologically for HLA class I (A and B loci) and immunogenetically for HLA class II (DR locus).

RESULTS

At 4 years postoperatively, the ratio of clear and rejection-free graft survival was 92% in group I and 66% in group II (Kaplan-Meier estimation, log rank test, P=0.03). Monovariate analysis in the Cox model gave no influence of solitary HLA class I or II matching, but only an influence of combined HLA class I and II matching (P=0.03).

CONCLUSIONS

In this monocentre study with proper typing techniques, the beneficial effect of HLA class I plus II matching on clear and rejection-free graft survival could be demonstrated in a homogeneous group of normal-risk keratoplasty patients.

Clinical responses of the corneal endothelium

The corneal endothelium maintains corneal deturgescence and clarity by a pump-leak mechanism first described by David Maurice. This cell layer can be investigated clinically with specular microscopy, fluorophotometry, and pachymetry. We describe the clinical responses of the corneal endothelium to aging, drugs, glaucoma, contact lens wear, trauma, disease, and surgery.

Beneficial effect of matching at the HLA-A and -B amino-acid triplet level on rejection-free clear graft survival in penetrating keratoplasty

OBJECTIVE

The beneficial effect of human leukocyte antigen (HLA) matching on long-term prognosis in penetrating keratoplasty is now unequivocal but has to be weighed against the additional waiting period on an individual basis. HLAMatchmaker is a molecularly based algorithm for histocompatibility determination that can identify immunologically acceptable mismatches and thus potentially reduce time on the waiting list dramatically without negatively affecting prognosis.

METHODS

The HLAMatchmaker algorithm (triplet-string matching) was applied on each of 545 normal-risk keratoplasties for which complete HLA type was known at split-level resolution. Two homogeneous groups were defined. Group I consisted of the 147 penetrating keratoplasties with up to 13 triplet-string mismatches (the typical upper limit of foreign in case of a single HLA-A or HLA-B allele mismatch) and was compared to the remaining 398 patients with more triplet mismatches (group II) using the Kaplan-Meier method and log-rank statistics. Analysis of clear graft survival on the basis of conventional HLA-A and HLA-B matching was performed as well. Reduction of time on the waiting list as compared to conventional HLA-A and HLA-B matching was predicted individually.

RESULTS

Triplet-string matching yielded 85% rejection-free clear graft survival 3 years after penetrating keratoplasty in group I but only 76% in group II (P<0.05), whereas conventional HLA-A and HLA-B matching did not result in any statistically significant reduction of immune reactions because of lack of statistical power (P=0.08). Triplet-string matching (13 mismatches accepted) reduces median time on the waiting list by 80%.

CONCLUSIONS

Triplet-string matching seems to improve mid- to long-term prognosis in penetrating keratoplasties while simultaneously reducing time on the waiting list in most cases. It should thus be considered for histocompatibility determination in penetrating keratoplasty.

Is manual counting of corneal endothelial cell density in eye banks still acceptable? The French experience

AIM

To examine the differences in manual endothelial cell counting methods in French eye banks and to analyse whether these differences could explain some substantial discrepancies observed in endothelial cell density (ECD) for corneas made available for transplant.

METHODS

A questionnaire was sent to the 22 eye banks asking for details of the technical features of the light microscopes used, the microscope calibration, strategy for cell counting, the technical staff, and the method of presenting endothelial data.

RESULTS

All eye banks responded and 91% (20/22) used only manual counting methods, in real time, directly through a microscope, and 62 different technicians, with varying experience, were involved in such counting. Counting of cells within the borders of a grid that were in contact with two adjacent borders was the most common method (17/22, 77%). Of the eight banks (8/22, 36%) that did not calibrate their microscopes, six reported the highest ECD values. Of the 14 others (64%), six applied a "magnification correcting factor" to the initial cell counts. In five of these cases, the corrected ECD was lower than estimated on initial count. Most of the banks (12/22, 55%) counted 100 cells or less in one to six non-adjacent zones of the mosaic. 14 of the banks (14/22, 64%) also graded cell polymegethism while seven (7/22, 32%) also graded pleomorphism ("hexagonality").

CONCLUSIONS

Lack of microscope calibration appears to be the leading cause of variance in ECD estimates in French eye banks. Other factors such as differences in counting strategy, the evaluation of smaller numbers of cells, and the different extent of experience of the technicians may also contribute to intraobserver and interobserver variability. Further comparative studies, including cross checking and the outcome of repeated counts from manual methods, are clearly needed with cross calibration to a computer based image archiving and analysis system.

Automated tri-image analysis of stored corneal endothelium

BACKGROUND

Endothelial examination of organ culture stored corneas is usually done manually and on several mosaic zones. Some banks use an image analyser that takes account of only one zone. This method is restricted by image quality, and may be inaccurate if endothelial cell density (ECD) within the mosaic is not homogeneous. The authors have developed an analyser that has tools for automatic error detection and correction, and can measure ECD and perform morphometry on multiple zones of three images of the endothelial mosaic.

METHODS

60 human corneas were divided into two equal groups: group 1 with homogeneous mosaics, group 2 with heterogeneous ones. Three standard microscopy video images of the endothelium, graded by quality, were analysed either in isolation (so called mono-image analysis) or simultaneously (so called tri-image analysis), with 50 or 300 endothelial cells (ECs) counted. The automated analysis was compared with the manual analysis, which concerned 10 non-adjacent zones and about 300 cells. For each analysis method, failures and durations were studied according to image quality.

RESULTS

All corneas were able to undergo analysis, in about 2 or 7.5 minutes for 50 and 300 ECs respectively. The tri-image analysis did not increase analysis time and never failed, even with mediocre images. The tri-image analysis of 300 ECs was always most highly correlated with the manual count, particularly in the heterogeneous cornea group (r=0.94, p<0.001) and prevented serious count errors.

CONCLUSIONS

This analyser allows reliable and rapid analysis of ECD, even for heterogeneous endothelia mosaics and mediocre images.

Cornea procurement from very old donors: post organ culture cornea outcome and recipient graft outcome

AIM

To study the suitability of corneas from very old donors for graft after banking and their clinical and endothelial outcomes in recipients.

METHODS

419 corneas stored in organ culture were divided into group 1, donors under 85 years (330 corneas) and group 2, "very old" donors aged 85 years and over (89 corneas). Endothelial cell density (ECD) before and after organ culture, discard rate before and after storage, and clinical and endothelial outcomes of the 196 penetrating keratoplasties (PKP) (158 in group 1 and 38 in group 2) were compared in a prospective longitudinal study.

RESULTS

Initial ECD was lower in group 2 than in group 1 and elimination for low ECD was more frequent in group 2 (respectively 38% v 20.2%, p=0.001). At the end of storage, because very old corneas lost fewer ECs than younger ones (respectively 4.2% v 9.5%, p=0.022), ECD was comparable between the two groups. The corneas of very old donors had a poorer macroscopic appearance at procurement and during surgery. Despite this, in grafted patients, overall graft survival in groups 1 and 2 (respectively 87.4% v 80.6%, p=0.197), visual acuity, and ECD did not differ at completion of the study (mean follow up 25 months).

CONCLUSION

This study suggests that endothelial cell count during banking ensures that functional and cellular results of PKPs are not dramatically influenced by very old donor age. Considering Europe's ageing population, the very elderly should not be deemed off limits for corneal procurement.

Value of two mortality assessment techniques for organ cultured corneal endothelium: trypan blue versus TUNEL technique

BACKGROUND/AIM

It is known that trypan blue staining is not a good predictor of loss of corneal endothelial cells (ECs) during organ culture. As it is primarily an indicator of membrane integrity, it would also not be expected to identify ECs undergoing apoptosis. The aim of this study was to determine the ability of the in situ TdT dUTP mediated nick end labelling (TUNEL) technique to detect cell death in the corneal endothelium caused by apoptosis during organ culture, compared with conventional vital staining with trypan blue.

METHODS

31 human corneas were organ cultured at 31C for 3-35 days. Staurosporine was used to induce apoptosis in five control corneas. The endothelium was assessed by trypan blue and by the in situ TUNEL technique. The percentages of trypan and TUNEL positive ECs were compared. Their links with sex, donor age, time from donor death and organ culture, initial and final EC density and cell loss were studied.

RESULTS

TUNEL stained ECs were observed in all corneas. TUNEL positive ECs were mostly located either in corneal folds or at the periphery of corneal folds showing central shedding. The mean percentage of cell death at the end of storage, assessed by the trypan blue technique, was 1.47% (SD 2.63, range 0.03-12); assessed by the TUNEL technique it was 12.7% (SD 16.4 range 0.6-65.5). There was a significant correlation between the two techniques (r = 0.7, p<0.001). The percentage of TUNEL stained ECs was correlated negatively with EC density at the end of storage (r = -0.47, p <0.005) and positively with percentage EC loss during storage (r = 0.46, p < 0.05).

CONCLUSION

This study demonstrates that organ cultured corneas systematically carry non-viable ECs that are implicated in cell death by apoptosis and go undetected when trypan blue staining is used. Because the in situ TUNEL assay detects earlier events in the cell death process than does trypan blue, it should be used to quantify endothelial viability, especially for experiments with new storage media.

Influencing factors on chronic endothelial cell loss characterised in a homogeneous group of patients

BACKGROUND/AIM

Advanced donor age, long death to excision time interval, and factors related to organ culture can trigger unfavourable intracellular processes in the graft endothelium and contribute to chronic endothelial cell loss after penetrating keratoplasty. The aim of this study was to investigate factors influencing chronic endothelial cell loss in a homogeneous group of patients.

METHODS

177 patients after first normal risk keratoplasties for keratoconus were retrospectively selected from the quality control database of our clinic. For 71 of them at least four central endothelial cell density values were documented in follow up. From these patients, only those 53 without any further intraocular procedures, without glaucoma, and without graft rejection were considered. A scatter plot of logarithmised endothelial cell density values against postoperative time was drawn for each patient. The slope of the regression line then equals the constant of decay in central endothelial cell density. The influence of donor age and storage time in organ culture on this index value of cell loss was investigated by means of linear regression analysis.

RESULTS

Mean loss of central endothelial cell density was 16.7% per year. Regression analysis revealed a statistically significant negative linear effect of both postmortem time (beta = -0.324; p = 0.014) and donor age (beta = -0.282; p = 0.036) and a trend for storage time in organ culture (beta = -0.195; p = 0.142) in a combined linear regression model.

CONCLUSION

Increased postmortem time and advanced donor age exert a significant negative effect on chronic endothelial cell loss. Storage time in organ culture seems to be third influencing factor. These negative influences may be reduced by compensating advanced donor age with minimised postmortem and storage time.

Outcome of Corneal transplantation rejection

PURPOSE

To identify predictive factors for reversibility of corneal graft rejection.

METHODS

The study design was a prospective cohort study. Among 440 consecutive penetrating keratoplasties performed at our institution, 79 grafts from 79 patients who developed signs of transplant rejection were included. Donor, recipient, surgical, and rejection variables were studied, at both univariate and multivariate levels.

RESULTS

The rate of reversibility was 51% (40/79). The average postoperative time of rejection was 10.5 +/- 9.3 months, and the average time of visual acuity recovery in patients with reversible rejection was 2.4 +/- 2.3 months. In logistic regression, only two variables significantly influenced the rate of reversibility. The preoperative diagnosis (p = 0.04) influenced the rate of rejection reversibility; patients with bullous keratopathy or regraft were more likely to experience irreversible rejection than patients with keratoconus or Fuchs' dystrophy. The average graft thickness at the time of rejection diagnosis was 774 +/- 129 microm in patients with irreversible rejection and 681 +/- 118 microm in patients with reversible rejection (p = 0.001).

CONCLUSION

Rejection was reversible in half of the cases. Rejection was more likely to be irreversible in patients with marked increase in graft thickness and in patients transplanted for bullous keratopathy or graft failure. Donor variables did not influence rejection reversibility.