Do Donated Corneas Become Transplanted Corneas? The Causes of Discard in Southern Brazil

Factors associated with the quality of corneas retrieved for transplantation by Eye Banks: a scoping review protocol

INTRODUCTION

The cornea is an avascular and transparent layer of connective tissue crucial to retinal image quality. Diseases can impair its quality, affecting vision. Keratoplasty is the only therapy capable of restoring vision quality in severe corneal involvement. Despite the established practice of transplantation, access to corneal tissue is limited in many places, and the quality of retrieved corneas is not always adequate, resulting in disqualification. Not all factors affecting tissue quality are fully understood due to the multifactorial nature of processes and variations in procedures globally.

OBJECTIVE

The objective is to map the global literature to establish the factors associated with the clinical and sociodemographic conditions of donors, and the conditions inherent in the processing of corneas that can influence the quality of this tissue for transplantation purposes.

METHODS AND ANALYSIS

A scoping review will be developed based on the methodological framework of the Joanna Briggs Institute. The scientific report will follow the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension checklist for Scoping Reviews. Searches will be conducted in 30 indexed and 12 grey literature databases, without time or location restrictions. The selection of studies will be carried out in three distinct phases: screening, eligibility and inclusion. After defining the sample, data from the selected studies will be systematically extracted into an electronic spreadsheet. The results will be presented descriptively through tables and graphs of absolute and relative frequency. In addition, the PRISMA Scoping Review flow chart will be presented to present the process of searching, including and excluding articles and documents.

ETHICS AND DISSEMINATION

This scoping review study does not require prior ethical approval as it uses publicly available and already published studies. The research protocol is registered in the Open Science Framework (osf.io/bw6r7). The findings will be submitted for publication in peer-reviewed scientific journals and presented at ophthalmology and/or transplantation conferences through oral presentations or posters.

Donut-shaped Corneal Allogeneic Intrastromal Segment as an Alternative to Deep Anterior Lamellar Keratoplasty in Advanced Keratoconus

PURPOSE

The aim of this study was to describe a new technique of selective corneal stromal transplantation for keratoconus treatment, donut-shaped CAIRS (corneal allogeneic intrastromal ring segment).

METHODS

A donut-shaped corneal graft is obtained using a double-bladed trephine. Descemet membrane, endothelium, and epithelium are all removed from the graft. Only stromal tissue is transplanted. A wide 360-degree intrastromal tunnel is created using the femtosecond laser, with a 30-degree angulation. The diameter is from 5.4 mm to 8 mm optical zone. After dehydration, the corneal graft is inserted into the tunnel. We report the clinical and tomographic outcomes after the procedure in 3 patients.

RESULTS

The mean follow-up time after donut-shaped CAIRS was 6.01 ± 1.02 months. In case 1, best spectacle-corrected visual acuity improved from 20/150 to 20/40. In case 2, it improved from 20/400 to 20/40, and in case 3 from 20/200 to 20/40. The mean preoperative K was 57.3 ± 4.5 D and reduced to 44.2 ± 2.5 D after donut-shaped CAIRS. The mean spherical equivalent decreased from -9.8 ± 3.2 preoperatively to -3.2 ± 2.2 postoperatively. No intraoperative or postoperative complications were observed. Anterior segment OCT showed a mid-stroma implant, fusiform in shape, equidistant from the epithelium and endothelium.

CONCLUSIONS

Donut-shaped CAIRS is a variation of the traditional CAIRS technique and showed to be an alternative option for keratoconus treatment, especially in moderate to advanced cases with a central clear cornea without scars. The technique is minimally invasive, and the visual axis remains untouched.

Gomes J, Güell JL, Casaroli-Marano RP. Corneal Endothelial Cell Cultures from Organotypic Preservation of Older Donor Corneas Are Suitable for Advanced Cell Therapy

INTRODUCTION

The purpose of this work was to evaluate the in vitro growth capacity and functionality of human corneal endothelial cells (hCEC) expanded from corneas of elderly (>60 years) donors that were preserved using an organotypic culture method (>15 days, 31°C) and did not meet the clinical criteria for keratoplasty.

METHODS

Cell cultures were obtained from prior descemetorhexis (≥10 mm) and a controlled incubation with collagenase type I followed by recombinant trypsin. Cells were seeded on coated plates (fibronectin-albumin-collagen I) and cultures were expanded using the dual supplemented medium approach (maintenance medium and growth medium), in the presence of a 10 μm Rho-associated protein kinase inhibitor (Y-27632). Cell passages were obtained at culture confluency (∼2 weeks). A quantitative colorimetric WST-1 cell growth assay was performed at different time points of the culture. Morphometric analysis (area assessment and circularity), immunocytochemistry (ZO-1, Na+/K+-ATPase α, Ki67), and transendothelial electrical resistance (TEER) were performed on confluent monolayers.

RESULTS

There was no difference between the cell growth profiles of hCEC cultures obtained from corneas older than 60 years, whether preserved cold or cultivated organotypic corneas. Primary cultures were able to maintain a certain cell circularity index (around 0.8) and morphology (hexagonal) similar to corneal endothelial mosaic. The ZO-1 and Na+/K+-ATPase pump markers were highly positive in confluent cell monolayers at 21 days after isolation (passage 0; P0), but significantly decreased in confluent monolayers after the first passage (P1). A weak expression of Ki67 was observed in both P0 and P1 monolayers. The P0 monolayers showed a progressive increase in TEER values between days 6 and 11 and remained stable until day 18 of culture, indicating a state of controlled permeability in monolayers. The P1 monolayers also showed some functional ability but with decreased TEER values compared to monolayers at P0.

CONCLUSIONS

Our results indicate that it is possible to obtain functional hCEC cultures in eye banks, using simplified and standardized protocols, from older donor corneas (>60 years of age), previously preserved under organotypic culture conditions. This tissue is more readily available in our setting, due to the profile of the donor population or due to the low endothelial count (<2,000 cells/mm2) of the donated cornea.

Penetrating Keratoplasty: Indications and Graft Survival by Geographic Region

Corneal transplantation, or penetrating keratoplasty (PK), is the most common form of solid-organ transplantation performed worldwide. Here, we evaluated the indications for PK and rates of transplant survival around the world by geographic region. We conducted a literature search of PubMed, MEDLINE, and Google Scholar databases and identified 155 relevant studies from 41 countries published between 1987 and 2021. The most common indications for PK were keratoconus in Europe, Africa, the Middle East, Australia, New Zealand, and Central and South America, bullous keratopathy in North America, and corneal scarring in Asia. The overall global mean graft survival rates at 1-, 2-, 3-, 5-, and 10-years were 88.6%, 81.2%, 78.9%, 72.8%, and 61.2%, respectively. Through this systematic analysis of PK by region, we hope to bring a new perspective to the corneal transplantation literature and to potentially highlight global differences and unmet needs in patient care.

Donation Process and Evaluation of Corneal Tissue in a Slit Lamp

BACKGROUND

The process of capturing and classifying the viability of corneal tissue for corneal transplantation is complex. The biomicroscopic examination is one of the techniques used to evaluate the quality of corneal tissues. The aim of this study was to analyze the relationship between the evaluation criteria used in biomicroscopic examination using a slit lamp and the classification of the quality of corneal tissue.

METHODS

This is a longitudinal, retrospective cohort study, performed at the Human Ocular Tissue Bank in the state of Rio Grande do Norte, Brazil. The sample consisted of 419 corneas donated between 2005 to 2016.

RESULTS

After the evaluation, the 419 corneas were classified as excellent (8 -1.91%), good (217 - 51.79%), regular (85 - 20.29%), and bad (109 - 26.01%). The classification of corneal quality attributed by ophthalmologists considered 13 criteria: senile arch, scars, epithelial defect, epithelial exposure, stromal infiltrate, subepithelial opacity, pterygium, Descemet's folds, stromal edema, stromal streak, cornea guttata, specular reflex, and cell loss endothelial. The quality of the cornea classified as excellent and good showed a statistically significant association (P value < .05) with senile arch, scar, epithelial defect, epithelial exposure, Descemet's folds, stromal edema, stromal streak, cornea guttata, specular reflex, and losses of endothelial cells; they had evaluated criteria that were absent or slightly present.

CONCLUSIONS

The evaluation of the corneal quality for corneal transplantation should involve the implementation of reliable techniques and trained, qualified professionals. There is a need to create evaluation instruments that consider the criteria according to their degree of interference in the quality of corneal tissue.

Effect of Donor Age and Corneal Endothelial Cell Density on Non-utilization of Donor Corneal Tissues: A Study From Indian Eye Banks

PURPOSE

To study the causes of non-utilization of donor corneas and assess whether non-utilized tissues differ from utilized tissues with regard to age and endothelial cell density (ECD).

METHODS

Aretrospective, cross-sectional analyses of all donor corneas collected from a network of 4 eye banks of a tertiary eye care institute in India during a 1-year period (January to December 2019) was conducted. All donor corneas were assessed for tissue quality by slit lamp evaluation, donor age, and specular microscopy. The causes of non-utilization and effect of donor age and ECD on tissue utilization were studied.

RESULTS

A total of 10,969 corneas were harvested during the study period; 4618 (42.1%) tissues were discarded. The main causes of non-utilization were poor tissue quality accounting for 86.16% (n = 3979) of all discarded corneas. The mean donor age was 50.7 ± 2.9 years and 63.3 ± 2.3 years for used and discarded corneas, respectively (P < 0.0001). The mean ECD of donor tissues was significantly (P < 0.0001) higher in the utilization group (2787.3 ± 77.4 cells/mm2) than that in the non-utilization group (2394.4 ± 82.5 cells/mm2). Donor age and ECD and their interaction were significant (P < 0.001) predictors of tissue utilization rate.

CONCLUSIONS

Donor age and ECD and their interaction were significantly associated with the rate of utilization of donor corneal tissues.

Analyse von Einflussfaktoren auf die Eignung von kornealem Spendergewebe in der LIONS Hornhautbank Saar-Lor-Lux, Trier/Westpfalz von 2006 bis 2016

Hintergrund und Ziel der Studie Vor dem Hintergrund des Missverhältnisses zwischen Hornhautverfügbarkeit und -bedarf war das Ziel der Studie, signifikante Einflussfaktoren auf die Eignung sowie die Verwerfungsgründe von kornealem Spendergewebe zu eruieren und damit die Rate verworfener Hornhäute langfristig zu reduzieren.

Patienten und Methoden 4140 Hornhäute von 2083 Spendern wurden zwischen 2006 und 2016 analysiert. Die untersuchten Einflussgrößen umfassten das Alter, das Geschlecht und die medizinische Vorgeschichte der Spender und Prozessierungsfaktoren wie die Post-mortem-Zeit. Die Daten wurden in eine Microsoft-Access-Datenbank übertragen und mittels logistischer Regressionsanalysen mit SPSS 20.0 statistisch ausgewertet. In einem multiplen Regressionsmodell wurden 6 Einflussfaktoren auf die Eignung des Spendergewebes analysiert. Alle Hornhäute, die nicht für eine elektive Keratoplastik infrage kamen, galten hierbei als ungeeignet.

Ergebnisse Ein hohes Spenderalter > 80 Jahre erwies sich im Vergleich zur Referenzgruppe der Spender < 40 Jahre als signifikant negative Einflussgröße auf die Eignung der Hornhaut (p = 0,001). Auch eine vorangegangene Kataraktoperation minderte signifikant die Eignung (p < 0,001). Männliche Hornhäute waren signifikant weniger geeignet als weibliche Hornhäute (p = 0,028). Ein Hypertonus in der Spendervorgeschichte (p = 0,612), eine vorangegangene Chemotherapie (p = 0,745) oder ein Diabetes mellitus (p = 0,321) zeigten keinen Einfluss auf die Eignung. Sepsis (p = 0,026) und Multiorganversagen (MOV; p < 0,001) als Todesursachen des Spenders resultierten in signifikant höheren Verwerfungsraten aufgrund von Kontamination des Kulturmediums. Hornhäute, bei denen die Blutentnahme mehr als 12 h seit Versterben des Spenders zurücklag, mussten signifikant häufiger wegen einer positiven Spenderserologie verworfen werden (p < 0,001).

Schlussfolgerungen Faktoren wie eine vorangegangene Kataraktoperation und ein hohes Spenderalter verringerten die Eignung des Spendergewebes. Ein Diabetes, ein Hypertonus und eine Chemotherapie in der Spendervorgeschichte zeigten keinen statistisch signifikanten Einfluss auf die Eignung. Todesursachen wie Sepsis und Multiorganversagen erhöhten die Kontaminationsrate des Kulturmediums. Eine postmortale Blutentnahme nach mehr als 12 h geht mit einem erhöhten Risiko für ein positives Serologieergebnis einher.