A new storage medium containing amphotericin B versus Optisol-GS for preservation of human donor corneas

A Comprehensive Review of Donor Corneal Preservation Strategies

ABSTRACT

Successful corneal transplantation relies on the viability of the corneal endothelium. Although various preservation systems have been developed in the field of eye banking, long-term storage of the corneal endothelium poses challenges and is costly. Optisol-GS in the past has been the most commonly used solution for intermediate-term corneal storage in the United States. However, disruptions in the availability of Optisol-GS, caused by rising costs and supply shortages, have necessitated alternative methods of corneal preservation. Previously described preservation methods include hypothermia (2-8°C) for short-term storage (7-14 days), organ culture (28-37°C) for intermediate storage (4-7 weeks), and cryopreservation for longer-term storage. In this review, we examine standard practice and alternative methods for corneal storage.

Culturing Limbal Epithelial Cells of Long-term Stored Corneal Donors (Organ Culture) In Vitro - A Stepwise Linear Regression Algorithm

PURPOSE

To assess various potential factors on human limbal epithelial cell (LEC) outgrowth in vitro using corneal donor tissue following long-term storage (organ culture) and a stepwise linear regression algorithm.

METHODS

Of 215 donors, 304 corneoscleral rings were used for our experiments. For digestion of the limbal tissue and isolation of the limbal epithelial cells, the tissue pieces were incubated with 4.0 mg/mL collagenase A at 37 °C with 95% relative humidity and a 5% CO2 atmosphere overnight. Thereafter, limbal epithelial cells were separated from limbal keratocytes using a 20-µm CellTricks filter. The separated human LECs were cultured in keratinocyte serum-free medium medium, 1% penicillin/streptomycin (P/S), 0.02% epidermal growth factor (EGF), and 0.3% bovine pituitary extract (BPE). The potential effect of donor age (covariate), postmortem time (covariate), medium time (covariate), size of the used corneoscleral ring (360°, 270°180°, 120°, 90°, less than 90°) (covariate), endothelial cell density (ECD) (covariate), gender (factor), number of culture medium changes during organ culture (factor), and origin of the donor (donating institution and storing institution, factor) on the limbal epithelial cell outgrowth was analyzed with a stepwise linear regression algorithm.

RESULTS

The rate of successful human LEC outgrowth was 37.5%. From the stepwise linear regression algorithm, we found out that the relevant influencing parameters on the LEC growth were intercept (p < 0.001), donor age (p = 0.002), number of culture medium changes during organ culture (p < 0.001), total medium time (p = 0.181), and size of the used corneoscleral ring (p = 0.007), as well as medium time × size of the corneoscleral ring (p = 0.007).

CONCLUSIONS

The success of LEC outgrowth increases with lower donor age, lower number of organ culture medium changes during storage, shorter medium time in organ culture, and smaller corneoscleral ring size. Our stepwise linear regression algorithm may help us in optimizing LEC cultures in vitro.

Assessment of performance and safety of Corneal Chamber hypothermic storage medium and PSS-L corneal rinsing solution in human and porcine corneas

PURPOSE

To prove the safety and performance of the hypothermic corneal storage medium "Corneal Chamber" and the rinsing solution "PSS-L" in support of the new Conformité Européenne (CE) certification process in accordance with the Medical Device Regulation.

METHODS

Fifteen (n=15) human donor corneas and 11 (n=11) porcine corneas were evaluated for the following parameters: endothelial cell density (ECD) and mortality, percentage of hexagonal cells (HEX%), coefficient of cellular area variation (CV%) and corneal transparency at Day 0 and after 14±1 days of storage in Corneal Chamber medium at 2-8°C. Then, the same parameters were assessed after rinsing of corneas in PSS-L for 1 min at room temperature. Evaluation of gentamicin sulfate carryover after corneal storage and PSS-L rinsing was performed by ultra-high performance liquid chromatography analysis on human corneas homogenates.

RESULTS

Human and porcine corneas stored in Corneal Chamber medium showed a good overall quality of the tissue according to the quality parameters evaluated. In particular, mean ECD, HEX% and CV% did not show statistically significant changes at the end of storage and endothelial mortality increased to 3.1±3.3 and 7.8±3.5% in human and porcine corneas, respectively. Tissue rinsing with PSS-L did not affect the quality parameters evaluated before and gentamicin sulfate residues were absent in human corneas.

CONCLUSIONS

Corneal preservation in Corneal Chamber medium at 2-8°C for 14 days and the corneal rinse with PSS-L are safe and effective procedures allowing the preservation of the corneal quality parameters as well as the complete elimination of gentamicin sulfate from the tissues before transplantation.Cite Now.

Comparison of corneal endothelial cell density and morphology with Optisol GS and Life4C storage media in the eye bank: a 5-year retrospective analysis

Purpose

Optisol GS and Life4C are corneal storage media used by eye banks worldwide. We sought to determine if either solution was associated with superior corneal endothelial cell density (ECD) or morphology in a large cohort of donor corneas.

Methods

From January 2016 through December 2020, 10,316 corneas from 5,624 unique donors were acquired and analyzed at Rocky Mountain Lions Eye Bank. In April 2019, Life4C replaced Optisol GS as the sole storage medium. We compared ECD and morphology before and after April 2019, and excluded corneas processed within the transition period. Univariable and multivariable regression analyses accounted for age, sex, tobacco use, heavy alcohol use, and diabetes. Only right corneas were analyzed to account for the correlation between eyes.

Results

Of 5042 right corneas analyzed, 3486 were stored in Optisol GS and 1556 in Life4C. There was no significant difference in ECD across groups (2794 vs. 2793 cells/mm2 in Optisol GS and Life4C, p=0.88). In multivariate analyses, there was no significant difference in corneal ECD (0.6 cells/mm2 higher with Life4C, p=0.96) or hexagonality (0.22% higher with Life4C, p=0.31). However, the coefficient of variation was significantly lower in the Life4C group (-0.0039, p=0.03). After adjustment for above factors, corneas in Life4C demonstrated a 3.1% decreased likelihood of exhibiting CV values greater than 0.40 (p=0.009).

Conclusions

This study demonstrates comparable and favorable outcomes using both storage media and confirms their overall efficacy. The decreased CV in Life4C is not of clinically significant magnitude, but merits further research in clinical and long-term settings.

Prospective In Vitro Comparison of Kerasave and Optisol-GS Corneal Storage Solutions

PURPOSE

The aim of this study was to compare the performance of Kerasave and Optisol-GS for hypothermic corneal storage for 14 days.

METHODS

This study was a prospective laboratory investigation. Mate corneas were recovered into Kerasave or Optisol-GS (27 pairs) and stored at 2°C to 8°C for 14 days. Corneas were evaluated by trained eye bank technicians, and study parameters were compared between the initial and final evaluations. Endothelial cell density (ECD), hexagonality (HEX), and coefficient of variation (CV) were evaluated by specular microscopy, and central corneal thickness (CCT) was examined by optical coherence tomography after 1, 3, 7, and 14 days of storage. Corneal transparency was scored using slit lamp examination at days 1 and 14.

RESULTS

Average ECD, HEX, and CV for the Kerasave (2653 ± 303 cells/mm 2 , 57 ± 4%, and 36 ± 3%) and Optisol-GS (2623 ± 306 cells/mm 2 , 57 ± 5%, and 36 ± 4%) groups were not significantly different at day 1. There was also no difference at any other study time points (all P > 0.05). ECD did not significantly change from day 1 to day 14 in either group ( P > 0.05), but a statistically significant change in HEX and CV was observed between day 1 and day 14 in both groups ( P < 0.01). Average CCT measured at day 1 for corneas stored in Kerasave was 622 ± 49 μm and those stored in Optisol-GS was 580 ± 35 μm ( P < 0.01). The difference in CCT measurements was not significantly different at day 14 (Kerasave: 674 ± 46 μm vs. Optisol-GS: 647 ± 58 μm, P > 0.05). Corneal transparency was not significantly different between the 2 groups at day 1 or day 14.

CONCLUSIONS

The corneal quality and clinically relevant parameters including ECD, endothelial morphometry, and corneal transparency were not different in corneas stored in Kerasave or Optisol-GS for 14 days. The initial difference in CCT between the 2 groups decreased at day 14. These results demonstrated that Kerasave corneal storage solution preserves the corneal endothelium similarly to Optisol-GS.

Donor related corneal graft infection: a review of literature and preventive strategies

PURPOSE

Donor-related infections are a serious threat to patient safety after corneal transplantation. We provide a concise review of literature from the last decade on donor-related graft infections, sources of contamination and means to reduce the contamination of donor tissue and preservation media.

METHODS

We reviewed 50 papers from year 2005 to 2021 related to donor-related graft infections. We included 14 studies related to the risk factors associated with post-keratoplasty infection and preventive methods.

RESULTS

Incidence of post-keratoplasty infections has been reported to be approximately 0.2%-0.77% for endophthalmitis and 6.5%-10.5% for microbial keratitis. We analyzed six important studies regarding the risk factors related to donor contamination. It was observed that younger donor age, increased death to retrieval time, warming cycles and increased eye bank processing time and positive corneo-scleral rim cultures were important risk factors for donor-related infections post keratoplasty. Eye banks have adapted newer protocols over the time period for prevention of donor-related contamination. Recommended preventive strategies were published in about eight important studies over the past decade. In addition to meticulous donor screening, rapid warming cycles, double contact with povidone iodine during retrieval and addition of antifungals like amphotericin B, Voriconazole and cycloheximide have been suggested over the last decade although their use is still in debate with regard to the efficacy, toxicity and cost-effectiveness.

CONCLUSION

The last decade has witnessed a relative rise of fungal infections and multidrug resistant bacterial infections post-keratoplasty. Eye bank prepared corneas for lamellar surgeries are at increased risk for donor contamination due to increased exposure to the higher temperatures during their processing. Addition of antifungals and broad spectrum antibiotics to the hypothermic preservation media needs to be considered in the new era of increasing trends of lamellar keratoplasty.

Cold Storage Media versus Optisol-GS in the Preservation of Corneal Quality for Keratoplasty: A Systematic Review

Optisol-GS is the most widely used pharmaceutical composition to preserve corneas for transplantation. This systematic review investigated the effects of different cold corneal storage media (CCSM) compared with Optisol-GS on the quality of stored corneas. The literature was searched throughout May 2022 on six databases and grey literature. Studies including corneas (population) exposed to distinct cold storage media (exposure) and Optisol-GS (comparison) that reported qualitative and/or quantitative parameters of cornea quality (outcome) were included. Methodological quality was assessed using ToxRTool. From 4520 identified studies, fourteen were included according to the eligibility criteria, comprising 769 evaluated cornea samples comparing Optisol-GS with commercial and noncommercial media. All studies showed good methodological quality. Experimental times ranged from 1–28 days, mainly using 4 °C as the preservation temperature. Viable endothelial cell density (ECD) and endothelial cell morphology (EC) were the most assessed parameters. ECD results for Cornisol were higher than Optisol-GS in 10 days (p = 0.049) and favored Cornea ColdTM up to 4 weeks (p < 0.05), which also showed better qualitative results. While the standardization of test protocols could improve comparisons, evidence indicates that most CCSM present similar performances on cornea preservation for transplantation at seven days, while some formulations may increase preservation at extended times.

Killing efficacy of a new hypothermic corneal storage medium against the micro-organisms frequently found in human donor cornea intended for transplantation

Objective

To study the in vitro killing efficacy of Kerasave (AL.CHI.MI.A Srl), a medium provided with amphotericin B tablet for hypothermic storage of human donor corneas, against relevant contaminants associated with postkeratoplasty infections.

Methods and Analysis

The antimicrobial activity of Kerasave was determined after 0, 3 and 14 days of incubation at 2°C-8°C, inoculating Kerasave and the control medium with 10⁵-10⁶ colony forming units (CFU) of Candida albicans (CA), Fusarium solani (FS), Aspergillus brasiliensis (AB), Staphylococcus aureus (SA), Enterococcus faecalis (EF), Bacillus subtilis spizizenii (BS), Pseudomonas aeruginosa (PA), Enterobacter cloacae (EC) and Klebsiella pneumoniae (KP). Log₁₀ reductions at different time intervals were determined by assessing the number of viable CFU using the serial dilution plating technique.

Results

After 3 days, Kerasave induced the highest log₁₀ decrease in the concentrations of KP, PA, CA and EC (5.37, 4.15, 2.97 and 2.67, respectively; all p<0.001). The log₁₀ decreases of SA and EF were 2.27 and 2.11, respectively (all p<0.001). The lowest log₁₀ decrease was observed in BS, AB and FS concentrations (0.25, 0.30 and 0.67, respectively; p<0.001 for BS and AB and p=0.004 for FS). After 14 days, the microbial count of CA, FS, SA, EF, PA and EC further decreased (p=0.006 for FS; p<0.001 for the others).

Conclusion

Kerasave effectively reduced or kept unchanged the microbial concentration of almost all tested strains after 3 days. Thus, this novel medium represents a valuable tool to control the microbial contamination of human donor corneas during hypothermic storage for up to 14 days before transplantation.