[The 2021 Activity Report of the Tissue Transplantation and Biotechnology Section of the German Ophthalmological Society]. / Aktivitäten der Sektion Gewebetransplantation und Biotechnologie der Deutschen Ophthalmologischen Gesellschaft: Leistungsbericht 2021.

The Section on Tissue Transplantation and Biotechnology of the German Ophthalmologic Society presented its 11th annual report for the year 2021. The number of corneal samples has still risen in comparison to former years. Nevertheless, there is still a need for import of transplants from abroad. Therefore, the transplant bottleneck has not yet been eliminated.

Comparison of Total Immunoglobulin G in Ante- and Postmortem Blood Samples from Tissue Donors.

BACKGROUND: A serology testing for infectious diseases (HIV, hepatitis B and C, syphilis) is mandatory in tissue donors. In many donors postmortem blood is the only sample available. Even though serological tests and nucleic acid amplification tests (NAT) used are validated for postmortem blood, a characterization of those blood samples is not yet established. We therefore investigated the total immunoglobulin G (IgG) content in postmortem blood of tissue donors and compared it to a corresponding antemortem blood sample. METHODS: Ante- and postmortem blood samples were obtained from 100 consecutive tissue donors. The total IgG of all samples was measured using an immune-turbidometric test on the AU 480 Chemistry Analyzer (Beckman Coulter). RESULTS: The mean total IgG concentration of antemortem blood samples from all 100 donors was 8.9 g/L ± 3.7 g/L (median 8.9 g/L, range 1.5 to 23.8 g/L). In 80 donors the IgG concentration in the antemortem blood sample was within the normal range with values ≥6 g/L (mean 10.0 g/L ± 3.3 g/L, median 9.3 g/L,). The total IgG concentration of the postmortem blood samples was lower with 7.2 g/L ± 3.2 g/L (median 6.7 g/L, range 0.6 to 18.2 g/L). The difference between the values of the antemortem and postmortem blood samples was 1.7 g/L ± 2.6 g/L (16.3%) (median 1.6 g/L, range -7.7 to 10.1 g/L). In 36 donors this difference was less than 10%, in 23 it was between 10 and 25%, in 33 between 26 and 50%, and in 8 over 50%. In 57 donors the total IgG in the postmortem blood sample was within the normal range with ≥6 g/L, in 53 of them also the value of the antemortem blood sample was within the normal range. No correlation for total IgG was found regarding the donor characteristics (age, sex, disease) and the sample characteristics (hemolysis, postmortem time). CONCLUSION: Total IgG values in antemortem samples were below the lower limit of 6 g/L in 20% of the cases. Total IgG was significantly lower in the postmortem samples compared to the antemortem samples, while 57% were still above the lower limit. No correlation with the postmortem time could be found. This lowered IgG levels should be payed attention to when using postmortem blood for infectious serology testing. Additional NAT testing should be considered.

SARS-CoV-2: Impact on, Risk Assessment and Countermeasures in German Eye Banks.

INTRODUCTION: Since the beginning of the COVID-19 pandemic there has been some debate regarding the risk of transmission through tissue transplantation and tissue banking processes. AIM OF THE STUDY: To analyze the changes that SARS-CoV-2 has caused regarding the harvesting of corneal donor tissue and eye bank activities in Germany. METHODS: A questionnaire was provided to 26 eye banks in Germany, consisting of questions about adaptations made in the screening of potential donors and the harvesting of corneal tissue following the pandemic spread of SARS-CoV-2. RESULTS: Eighteen eye banks actively reduced recruitment of donors and two banks ceased all activity. Additional diagnostic screening was performed in eight banks, using conjunctival swabs and/or nasopharyngeal swabs. In six eye banks, additional protective measures, such as FFP2 masks and/or facial shields, were implemented. Overall, a mean reduction in the number of obtained donor tissues of 17% was observed. DISCUSSION: Conjunctival and/or nasopharyngeal swabs of donors have been implemented by a minority. Reasons for not performing additional tests may be moderate sensitivity and lack of validation for postmortem use of RT-PCR testing. Also, the hazard of SARS-CoV-2 entering the corneal donor pool with subsequent transmission might be perceived as theoretical. Face shields provide a sufficient barrier against splash and splatter contamination but may be insufficient against aerosols. Additional face masks would provide support against aerosols, but it remains debatable if corneal harvesting can be considered an aerosol-producing procedure. In the future we expect to see changes in current guidelines because of a surge in scientific activities to improve our understanding of the risks involved with cornea donation in the COVID-19 pandemic, and because current practice may reduce the availability of donor corneas due to new exclusion criteria while the demand remains unchanged.

Pseudophakic corneal donor tissue in Descemet membrane endothelial keratoplasty (DMEK): implications for cornea banks and surgeons.

OBJECTIVE: Increasingly, cornea banks are recovering donor tissue from pseudophakic donors. Little is known about their suitability for Descemet membrane endothelial keratoplasty (DMEK) surgery in terms of endothelial cell density (ECD) and preparation failure. METHODS AND ANALYSIS: We explored ECD during donor tissue preparation in 2076 grafts. Preparation failure was analysed in 1028 grafts used in DMEK surgery at our clinic. To monitor ECD and functional results, we matched 86 DMEK patients who received pseudophakic donor grafts with similar recipients of phakic donor grafts and followed them up for 36 months. RESULTS: At recovery, mean ECD in pseudophakic donor grafts was 2193 cells/mm2 (SD 28.7) and 2364 cells/mm2 (SD 15.7) in phakic donor grafts (p<0.001). After cultivation, the difference increased as pseudophakic donor grafts lost 14% of ECD while phakic lost only 6% (p<0.001). At transplantation, mean ECD in pseudophakic donor grafts was 2272 cells/mm2 (SD 250) and 2370 cells/mm2 (SD 204) in phakic donor grafts (p<0.001). After transplantation, the difference in ECD increased as pseudophakic donor grafts lost 27.7% of ECD while phakic donor grafts lost only 13.3% (p<0.001). The risk of preparation failure in pseudophakic donor grafts was higher than in phakic donor grafts (OR 4.75, 95% CI 1.78 to 12.67, p=0.02). Visual acuity increased in both groups similarly. CONCLUSIONS: Pseudophakic donor grafts have a lower ECD, are more prone to endothelial cell loss during recovery and surgery and are associated with a higher risk of preparation failure. Cornea banks and surgeons should consider this in the planning of graft preparation and transplantation.

Investigation of Visual System Involvement in Spinocerebellar Ataxia Type 14.

Spinocerebellar ataxia type 14 (SCA-PRKCG, formerly SCA14) is a rare, slowly progressive disorder caused by conventional mutations in protein kinase Cγ (PKCγ). The disease usually manifests with ataxia, but previous reports suggested PRKCG variants in retinal pathology. To systematically investigate for the first time visual function and retinal morphology in patients with SCA-PRKCG. Seventeen patients with PRKCG variants and 17 healthy controls were prospectively recruited, of which 12 genetically confirmed SCA-PRKCG patients and 14 matched controls were analyzed. We enquired a structured history for visual symptoms. Vision-related quality of life was obtained with the National Eye Institute Visual Function Questionnaire (NEI-VFQ) including the Neuro-Ophthalmic Supplement (NOS). Participants underwent testing of visual acuity, contrast sensitivity, visual fields, and retinal morphology with optical coherence tomography (OCT). Measurements of the SCA-PRKCG group were analyzed for their association with clinical parameters (ataxia rating and disease duration). SCA-PRKCG patients rate their vision-related quality of life in NEI-VFQ significantly worse than controls. Furthermore, binocular visual acuity and contrast sensitivity were worse in SCA-PRKCG patients compared with controls. Despite this, none of the OCT measurements differed between groups. NEI-VFQ and NOS composite scores were related to ataxia severity. Additionally, we describe one patient with a genetic variant of uncertain significance in the catalytic domain of PKCγ who, unlike all confirmed SCA-PRKCG, presented with a clinically silent epitheliopathy. SCA-PRKCG patients had reduced binocular vision and vision-related quality of life. Since no structural retinal damage was found, the pathomechanism of these findings remains unclear.

Increased sensitivity of microbiological testing of cornea organ culture medium by additional resin treatment.

OBJECTIVE: This validation study investigates the treatment of cornea organ culture medium (Modified Eagle Medium, Biochrom GmbH, Berlin, Germany) with RESEP, a new medical device for antibiotics removal, before microbiological testing with BACTEC TM blood culture bottles. METHODS AND ANALYSIS: 10-100 colony forming units of Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Bacillus subtillis, Aspergillus brasiliensis, Clostridium sporogenes, Enterobacter cloacae and Staphylococcus epidermidis were inoculated in 9mL of cornea organ culture medium. In group A, the medium was withdrawn with RESEP and treated for 20 min at room temperature, and then inoculated in BACTEC Plus Aerobic/F/Anaerobic/F blood culture bottles. In group B, the medium, spiked by the inoculation of microorganism, was injected directly. For each strain, a growth control was performed, by direct inoculation of the microorganisms in BACTECTMvials (positive control). All samples were incubated in the automated BACTECTMblood culture system at 36°C ±1°C for maximum of 14 days or until a positive reading. The elimination of antibiotics from the medium by RESEP was determined by high-performance liqiud chromatography. RESULTS: After 20 min of RESEP treatment, 100% (n=9) of streptomycin, 100% (n=9) of amphotericin B and 99.7% (n=9) of penicillin G were eliminated. In group A, all microorganisms were detected within 3 days of incubation with a sensitivity of 100% (n=99) and showed no significant delay compared with the positive controls. In group B, the overall sensitivity was 67.9% (n=96) with a significant delay until detection of microbial growth for all tested microorganisms except for A. brasiliensis. CONLCLUSION: The use of RESEP to eliminate the antibiotics from cornea organ culture medium increases the sensitivity of the microbiological testing with BACTECTMPlus blood culture bottles significantly and fulfils the requirements of the European Pharmacopoeia method suitability test.

Primary Descemet's Membrane Endothelial Keratoplasty for Fuchs Endothelial Dystrophy versus Bullous Keratopathy: Histopathology and Clinical Results.

PURPOSE: To investigate functional and anatomical results up to 12 months after Descemet's membrane endothelial keratoplasty (DMEK) for Fuchs' endothelial dystrophy (FED) versus bullous keratopathy (BK) in consideration of morphologic characteristics on host's endothelium-Descemet's membranes (EDM). METHODS: In a prospective consecutive case series, 119 eyes underwent a primary DMEK for FED or BK. Intraoperatively obtained EDM were investigated immunohistologically. Clinical and morphological parameters were compared between FED and BK. RESULTS: Overall, the 12-months best-corrected visual acuity (BCVA) was 0.14 logMAR, and 0.10 logMAR in eyes without vision-limiting comorbidities; thereby no differences were revealed between eyes with FED and BK up to 12 months postoperative (p = 0.186 and p = 0.095, respectively). Correspondingly, the mean central corneal thickness (CCT) measured 520 vs. 529 µm and the mean endothelial cell density (ECD) was 1743 vs. 1457 cells/mm2 for FED and BK, 12 months postoperative. Regarding CCT and ECD, no differences were observed between the groups (p = 0.181 and p = 0.112, respectively). The overall detachment rate was 40% (48/119). Comparing FED and BK the detachment rates did not differ, which were 41% vs. 39% and 43% vs. 35%, in pseudophakic eyes (p = 0.554 and p = 0.601, respectively). Yet, the distribution of recurring graft detachments differed between FED and BK; secondary re-detachments were more frequent in the FED group (7 cases). Regarding histologic investigations, a lower ECD was found in specimens with BK, no differences were revealed for EDM and anterior banded layer thicknesses. Immunohistologically, differences in the distribution of fibronectin and cytokeratin were observed. A rarification of matrix proteins was found in EDM complexes with FED. CONCLUSIONS: DMEK produces similar results for FED and BK. However, the postoperative course may differ with regard to the recurrence of secondary graft detachments that may be associated by histopathologic particularities.

FUNDUS AUTOFLUORESCENCE FINDINGS IN EARLY CHLOROQUINE MACULOPATHY.

BACKGROUND/PURPOSE: Toxic maculopathy is a rare but severe complication of chloroquine intake. Although the phenotype of established maculopathy was analyzed in detail, few data exist on the ophthalmologic findings in the early stage. METHODS: The authors present 4 female patients with unequivocal signs of chloroquine maculopathy (bilateral [peri-]central scotoma in the visual fields, structural alterations of the macula in the optical coherence tomography) but normal or atypical findings as to fundus autofluorescence imaging. RESULTS: In all patients, optical coherence tomography showed perifoveal thinning and subtle alterations of the outer retinal layers. In one patient, the latter was limited to the pericentral region, whereas it showed a more diffuse distribution in two other patients. One patient showed a combination of pericentral and diffuse damage. Multifocal electroretinography was recorded in three patients and revealed the typical (peri-)central amplitude reductions. CONCLUSION: A normal fundus autofluorescence does not rule out toxic maculopathy. Optical coherence tomography and multifocal electroretinography seem to be more sensitive in the early stage of the disease. In case of typical complaints and visual fields, the optical coherence tomography has to be evaluated for subtle alterations of the outer retina. Their presence justifies the cessation of the drug. Multifocal electroretinography may be of special value in these problematic cases.