Study of death to preservation time and its impact on utilisation of donor corneas

Effect of elevated irrigation bottle height during cataract surgery on corneal endothelial cells in porcine eyes

BACKGROUND

Cataract surgery induces corneal endothelial cell loss (ECL). This study investigates the relationship between bottle height (BH) and ECL induced due to irrigation and aspiration (I/A) in cataract surgery and quantifies protective effects of intraoperatively used ophthalmic viscoelastic substances.

METHODS

Intermittent I/A without phacoemulsification was performed in porcine eyes for 10 min with varying BHs of 100 cm (BH100), 125 cm (BH125), 150 cm (BH150) or no treatment (control, no I/A). Additionally, in one group a dispersive ophthalmic viscoelastic substance was injected into the anterior eye chamber before treatment with I/A at a BH of 150 cm (BH150 + V). After exposure of the corneal endothelium to I/A, the corneas were prepared to split corneal buttons on day 0 and cultivated for 15 days. Endothelial cell density (ECD) was analyzed blinded on days 1, 8 and 15.

RESULTS

Relative ECL significantly correlated with irrigation BH (control (n = 13): -9.69 ± 6.03% (average ± standard deviation); BH100 (n = 12): -9.69 ± 4.81%-p = 1.000; BH125 (n = 14): -19.44 ± 7.30% - p < 0.001; BH150 (n = 13): -21.99 ± 6.70%-p < 0.001). I/A-induced ECL was significantly decreased by the injection of ophthalmic viscoelastic, as BH150 + V (n = 14; -10.92 ± 4.09%-p = 1.000) showed a cell loss comparable to the control group.

CONCLUSIONS

ECL is altered by I/A BH and reduced when viscoelastic substances are used.

Impact of Donor, Recipient, and Graft Characteristics on Corneal Transplantation Outcomes

Purpose

Although several donor, recipient, and graft characteristics have been studied in relation to corneal transplantation outcomes, no study to our knowledge has assessed the impact of donor cooling times on postoperative outcomes longitudinally. With only one corneal graft available for every 70 needed worldwide, this study seeks to identify any factors that could alleviate this shortage.

Methods

Patients undergoing corneal transplantation at the Manhattan Eye, Ear & Throat Hospital over a 2-year period were retrospectively studied. Study metrics included age, diabetic history, hypertensive history, endothelial cell density, death-to-preservation time (DTP), death-to-cooling time (DTC), and time-in-preservation (TIP). Postoperative transplantation outcomes, including best corrected visual acuity (BCVA) at 6- and 12-month follow-up visits, need for re-bubbling, and need for re-grafting, were assessed. Unadjusted univariate and adjusted multivariate binary logistic regressions were performed to determine the association of cooling and preservation parameters with corneal transplantation outcomes.

Results

Among 111 transplants, our adjusted model found that DTC ≥4 hours was associated with significantly worse BCVA, but only at 6-month postoperative follow-up (odds ratio [OR]: 0.234; 95% confidence interval [CI]: 0.073-0.747; p = 0.014). By 12-month follow-up, DTC >4 hours was no longer associated with BCVA in a statistically significant manner (OR: 0.472; 95% CI: 0.135-1.653; p = 0.240). A similar trend was found at a DTC cutoff of ≥3 hours. None of the other studied parameters, including DTP, TIP, donor age, or medical history were significantly correlated with transplantation outcomes.

Conclusion

Longer DTC or DTP did not have a statistically significant effect on corneal graft outcomes after one year, though short-term outcomes were improved in donor tissues with DTC below four hours. None of the other studied variables correlated with transplantation outcomes. Given the global shortage of corneal tissue, these findings should be considered when determining suitability for transplantation.

Intraoperative optical coherence tomography-guided donor corneal tissue assessment and preparation

Purpose

To evaluate the role of intraoperative optical coherence tomography (i-OCT) in donor grading, selection, and preparation during different types of keratoplasty.

Methods

Seventy-one consecutive donor corneas collected over 6 months, after clinical grading, were observed by an experienced corneal surgeon under an i-OCT equipped microscope. The donor preparation (manual/automated) for different types of keratoplasty procedures was also undertaken under i-OCT.

Results

The mean central corneal thickness of optical and nonoptical grade tissues was 533 ± 19 and 662 ± 52 μm, respectively. The i-OCT-based grading matched with clinical grading in 98.5% cases. Irregular thickness, anterior stromal hyperreflectivity, and previous scars were appreciated in 1.4, 1.4, and 7.04% donors, respectively. During Descemet stripping automated endothelial keratoplasty, i-OCT facilitated selection of appropriate microkeratome head for automated donor preparation in all cases, besides allowing manual dissection of partially dissected lenticule, identification of site of inadvertent perforation, and eccentric trephination in one case each. During Descemet membrane endothelial keratoplasty, i-OCT-based assessment of preexisting scar (five cases) guided careful tissue selection (2/5) and preparation. During predescemetic endothelial keratoplasty, precise needle advancement allowed successful type-1 bubble formation in all cases. All manually punched donors demonstrated an extra endothelial ledge, while those with automated preparation showed tapering donor margins.

Conclusion

i-OCT might serve as a useful imaging tool for objective assessment of donor characteristics. The modality may complement clinical evaluation for donor grading, selection, and preparation.

Donor and recipient characteristics associated with rebubbling rate, endothelial cell loss, and graft failure in primary descemet membrane endothelial keratoplasty

Aim: To determine whether donor and recipient characteristics are associated with rebubbling rate, endothelial cell loss (ECL), and graft failure 3 years after primary Descemet membrane endothelial keratoplasty (DMEK). Material and Method: Records of 295 consecutive DMEK surgery and match with corresponding donor data were reviewed at a tertiary referral clinic. Recipients with intraoperative complications and coexisting ocular pathologies were excluded. Age, sex of donor and recipient, cause of donor death, death-to-preservation time (DtPT), storage time, donor endothelial cell density (ECD), and indications for surgery were analyzed for correlation with rebubbling rate, postoperative ECL, and graft failure. Further, subgroup analyses of the cause of death, donor sex, DtPT (median value, 3.5 h), and indications were performed. Multiple regression and receiver operating characteristics (ROC) analysis were used to determine the independent risk factors for graft failure. Results: This study included 114 eyes that underwent DMEK for bullous keratopathy (BK; 64%) and for Fuchs’ endothelial corneal dystrophy (FECD; 36%). The graft failure percentage was the only parameter that was higher in patients with DtPT > 3.5 h (p=0.047) than those with shorter DtPT. The probability of graft failure was seven times higher in eyes with DtPT > 3.5 h than with shorter DtPT (odds ratio 7.36, 95% confidence interval CI 1.34‒40.53) and 10 times higher in eyes with BK than those with FECD (odds ratio 10.29, 95% CI 1.01‒104.54). Conclusion:. DtPT and recipients with BK diagnosis were found to be independent risk factors for graft failure. Therefore, surgeons should consider DtPT for DMEK in eyes with BK.

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.

Keratitis following descemet's stripping endothelial keratoplasty (DSEK): Clinical features and outcome in early vs late presentation

OBJECTIVE

To compare the clinical presentation, risk factors, causative organisms, and final outcome of early- and late- onset microbial keratitis following Descemet's Stripping Endothelial Keratoplasty (DSEK).

MATERIALS AND METHODS

In a retrospective, comparative, case series, twenty-three (10 early-onset keratitis, 13 late-onset keratitis) cases were included for analysis from a single centre tertiary eye care setup. Data about demography, indication, clinical features, and outcome were collected for both the groups. Comparison of clinical presentation, risk factors, microbiology and final outcome were carried out.

RESULTS

The most common indication was failed graft. While all patients with late-onset keratitis presented with ulcerative keratitis, 60% of early-onset keratitis presented with ulcerative keratitis. Four patients in the early-onset group had interface keratitis. Associated endophthalmitis was more in the early-onset compared to the late-onset group. Early-onset interface keratitis cases are mostly associated with donor-related infection. Gram-positive bacteria were the most common organisms isolated from both early- and late- onset infection. Major surgical procedures in both early- and late- onset keratitis included lenticule removal (n = 4) and therapeutic penetrating keratoplasty (n = 5).

CONCLUSIONS

Failed graft is a major risk factor in post-DSEK keratitis. Interface keratitis and endophthalmitis are commonly observed in early-onset keratitis. A majority of the patients need surgical intervention.

Primary Graft Failure, Infection, and Endothelial Cell Density in Corneal Transplants With Increased Death-to-Preservation Time

PURPOSE

To ascertain whether death-to-preservation time (DPT) is associated with donor endothelial cell density (ECD), primary graft failure (PGF), and infection.

METHODS

Donor corneas aged older than 10 years with ECD 2000 to 4500 cells/mm2 were procured between 2011 and 2018 by a single eye bank. Donor corneas were analyzed retrospectively for the main outcome measures of PGF, infection, and ECD. Means and proportions of study parameters were compared between corneas with long and short DPT, defined as greater or less than 14 hours, respectively, excluding corneas with a history of intraocular surgery or diabetes. Multivariate analyses were performed using logistic regression, adjusting for donor age at time of death, history of diabetes mellitus, and history of cataract surgery.

RESULTS

Among 12,015 corneas, those with long DPT had a statistically but not clinically significant higher ECD than that of corneas with short DPT (2754 vs. 2724 cells/mm2, P < 0.01). There was no difference in PGF and infections in corneas with long versus short DPT (0.28% vs. 0.26%, P = 0.86; 0.43% vs. 0.29%, P = 0.51, respectively).

CONCLUSIONS

Longer DPT is not associated with a clinically meaningful reduction in donor ECD, PGF, or infection.

Effect of different human tissue processing techniques on SARS-CoV-2 inactivation-review

The safety of the tissue transplant recipient is a top priority for tissue banks, and the emergence of the new coronavirus SARS-CoV-2 has raised significant concerns about the risks of releasing tissue for clinical use. In the present study, we conducted a literature review about the potential infectivity of SARS-CoV-2 in different biological tissues and the influence of various tissue processing and sterilization procedures on viral inactivation. The search revealed that SARS-CoV-2 binds to the human angiotensin-converting enzyme receptor to penetrate human cells. These receptors are present in skin cells, musculoskeletal tissue, amniotic membranes, cardiovascular tissue and ocular tissues, including the cornea. In general, we found that coronaviruses are stable at low temperatures, and inactivated upon exposure to extreme heat and pH. Notably, gamma irradiation, which has already been employed to inactivate SARS and MERS, could be useful for sterilizing skin, amnion and musculoskeletal tissues against SARS-CoV-2. We conclude that due to the limited information about the effects of physical and chemical tissue processing methods on viral neutralization, rigorous donor screening is still essential for tissue transplant recipient safety.

Cornea Procurement and Processing up to 72 Hours: No Risk for Cornea Transplant Quality

Background

The realization of tissue donations is bound to a tight timeframe. Depending on the type of tissue, time limits are specified within which the donation must be procured and processed. Otherwise, there is a risk of tissue quality loss with increasing time intervals from cardiovascular arrest. According to the European Directorate for the Quality of Medicines and HealthCare (EDQM) guide, cornea must be procured and processed within 72 h after death. The question arises whether this time interval has an influence on the quality of transplanted tissues and how it affects the accomplishment of tissue donations.

Methods

In order to obtain information on this, the numbers of tissue donations in the network of the German Society for Tissue Transplantation (DGFG) were evaluated as a function of the death to retrieval time (DRT) as well as the death to preservation time (DPT). For this purpose, 21,454 database entries of cornea donations made in the period from 2014 to 2018 were included.

Results

The results show that nearly 50% of donations realized in the DGFG network could be processed only 48 h or later after cardiovascular death due to the opt-in regulation in Germany. For these donations, there seems to be a higher discard rate compared to donations taken earlier. Nevertheless, there is a transplantation rate for these grafts of more than 65%, which is comparable to average transplantation rates stated in the literature.

Conclusion

All corneas finally selected for transplantation must meet the specified quality parameters. Since this naturally also applies to transplants that could only be procured at later time points, it can be concluded that DPT up to 72 h for corneal tissue is adequate and has no influence on the quality of corneas that are ultimately transplanted.