Preliminary study of rabbits as an animal model of mammalian eye transplantation and literature review / Estudo preliminar de coelhos como modelo animal para transplante de olho em mamíferos e revisão da literatura

ABSTRACT Purpose: To describe an innovative animal model of eye transplantation used in rabbits. Methods: six Dutch-belted male rabbits were submitted to lateral orbitotomy in the right eye, wide retrobulbar anatomy exposure, dissection of the structures, identification and distal section of the optic nerve followed by anastomosis either by vicryl (group 1) or fibrin glue (group 2). Electroretinography recording was performed before the section of the optic nerve and every 30 seconds after, to monitor the function of retina. Left eye was used as control group. Results: After optic nerve resection and anastomosis, stable ERG amplitude of the right eye was lost after 302 seconds in group 1 and after 296 seconds on group 2. Left eye kept longer stable ERG amplitude curves. Conclusions: The animal model of whole eye transplantation was effective in describing a novel technique to be used in rabbits, with success of the anatomic procedure. Further studies will clarify the best anastomosis methods and maintenance of function of the receptor organ. Translational relevance: this animal model of whole eye transplantation provides a novel perspective for blind patients and the research models, since we describe a novel mammal animal model. This model can be used as basis of a human model of whole eye transplantation in future studies.

RESUMO Objetivo: Descrever uma técnica cirúrgica inovadora para transplante de olho em um modelo animal em coelhos. Métodos: Seis coelhos machos com Dutch Belted foram submetidos à orbitotomia lateral do olho direito, com ampla exposição da anatomia retrobulbar, dissecção do cone muscular, exposição e secção distal do nervo óptico seguida de anastomose por vicryl (Grupo 1) ou cola de fibrina (Grupo 2). O registro da eletrorretinografia foi realizado antes da secção do nervo óptico e a cada 30 segundos após, para monitorar a função da retina. O olho esquerdo foi usado como grupo controle. Resultados: Após a ressecção do nervo óptico, a estabilidade da amplitude da eletrorretinografia foi perdida no olho direito após 302 segundos no Grupo 1 e após 296 segundos no Grupo 2. O olho esquerdo manteve eletrorretinografia estável por períodos mais longos. Conclusão: O modelo animal de transplante total de olho foi eficaz em descrever uma nova técnica cirúrgica para ser utilizada em laboratório com coelhos, com sucesso do procedimento anatômico. Novos estudos esclarecerão os melhores métodos de anastomose e manutenção da função do órgão receptor.

Awareness Regarding Eye Donation and Effects of COVID-19 on Its Perception: A Community-Based Cross-Sectional Study From India.

OBJECTIVES: This study aimed to assess awareness toward eye donation and the effects of COVID-19 on perceptions about eye donation in an urban community of West Bengal, India. MATERIALS AND METHODS: Eligible adults residing in the area under study were chosen by simple random sampling and interviewed using a predesigned and pretested data collection schedule to assess awareness and perception. Based on their total awareness score, the participants were classified as having good awareness or poor awareness toward eye donation. RESULTS: Among 423 participants, 52.0% were male, 34.0% were 18 to 30 years old, 38.3% were educated up to secondary level, and 85.6% had eye disease in their family. Of total participants, 70.2% had heard about eye donation, with 59.9% of this group having knowledge of eye donation only after death and 57.9% having knowledge that donation must occur within 6 hours of death. In addition, 52.9% were aware about donation from home, 30.6% said only the cornea is transplantable, and 52.2% knew it can be preserved. Participants with higher education, higher socioeconomic status, and outside of the house occupational engagement had significantly higher chance of good eye donation awareness. Of total participants, 32.0% said that COVID-19 could be transmitted through eye donation, with 58.2% of participants opining that the pandemic was not a suitable time to consider donation of eyes. CONCLUSIONS: COVID-19 has had a negative impact on eye donation perceptions. Although most of our participants had heard about eye donation, their awareness regarding important aspects about eye donation were still lacking, thus calling for a more focused action plan and implementation of the same.

Meibomian Gland Dysfunction in Ocular Graft vs. Host Disease: A Need for Pre-Clinical Models and Deeper Insights

Despite decades of experience with hematopoietic stem cell transplantation, we are still faced with the delicate equipoise of achieving stable ocular health post-transplantation. This is because ocular graft-versus-host disease (oGvHD) following hematopoietic stem cell transplantation frequently occurs (≥50%) among transplant patients. To date, our understanding of the pathophysiology of oGvHD especially the involvement of the meibomian gland is still limited as a result of a lack of suitable preclinical models among other. Herein, the current state of the etiology and, pathophysiology of oGvHD based on existing pre-clinical models are reviewed. The need for additional pre-clinical models and knowledge about the involvement of the meibomian glands in oGvHD are emphasized.

Development of a New Large-Animal Model for Composite Face and Whole-Eye Transplantation: A Novel Application for Anatomical Mapping Using Indocyanine Green and Liquid Latex.

BACKGROUND: Recent advances in the field of vascularized composite allotransplantation have revolutionized reconstructive surgery and demonstrated opportunity for restoration of orbital content and perhaps vision. The development of an animal model that would facilitate study of surgical technique, nerve regeneration, vision restoration, and immunosuppression is needed. The aim of this study is to describe three different large-animal cadaveric models suitable for composite face and whole-eye transplantation. In addition, the authors introduce a novel colored liquid latex and indocyanine green mixture for vasculature identification and visualization. METHODS: The authors studied three different flap designs using cadaveric Yorkshire swine and modified them for face and whole-eye transplant harvest. Flaps harvested included a chimeric flap, a monobloc flap, and a bipedicled free flap. The authors injected selected vasculature with colored latex to better delineate vascular anatomy supplying the orbit and face. Indocyanine green was added to the latex solution to allow for visualization of the vascular supply using near-infrared imaging. RESULTS: Colored latex and indocyanine green injections were successfully visualized in all cadaveric dissections. All three modified flap designs showed a well-defined and consistent vascular network within each face and whole-eye transplantation flap using laser-assisted near-infrared imaging. CONCLUSIONS: The authors present the feasibility of composite face and whole-eye transplantation models using a novel mixture of liquid latex and indocyanine green in a porcine cadaver. Further study in large animals is needed to appraise the surgical feasibility of this procedure and potential for clinically relevant outcomes, including vision restoration. The authors believe this study establishes a foundation for translation into live animal models for optic nerve regeneration.

Knowledge and attitude towards eye donation among health professionals of northern India.

Background: We aimed to assess the knowledge and attitude of health professionals towards eye donation at an apex tertiary care centre of northern India. Methods: We interviewed 600 health professionals, comprising doctors, nurses, medical as well as nursing students, social workers and allied paramedical staff. A structured questionnaire (12 questions for assessing knowledge and 5 questions for assessing attitude) was used to estimate the awareness of eye donation and willingness to pledge eyes for donation. The responses pertaining to knowledge were graded as 'excellent', 'good' and 'poor' and those pertaining to attitude were grouped into 'positive' and 'negative'. Results: Of the 600 participants, 138 participants (23%) had 'excellent' knowledge and 234 participants (39%) had 'good' knowledge about eye donation. Awareness of eye donation was positively related to the level of literacy (odds ratio [OR] 8.5 [2.30-31.2]; p<0.001). Medical social workers and health supervisors had better knowledge about eye donation (OR 2.01 [1.08-3.72]; p=0.026) than other professional groups. Knowledge of eye donation had no significant association with age, gender, religion, family type and marital status of the respondent. Willingness to pledge eyes for donation was observed in only 6% of the participating health professionals. Pledging of eyes for donation was higher among older participants (OR 7.8 [2.67-22.77]; p<0.001). Conclusion: Our study shows that there is sufficient knowledge about eye donation, but an alarmingly low willingness to pledge eyes for donation among health professionals. Concerted efforts are required to alter their attitude to strengthen the Hospital Cornea Retrieval Programme.

Immunological considerations and concerns as pertinent to whole eye transplantation.

PURPOSE OF REVIEW: The advent of clinical vascularized composite allotransplantation (VCA), offers hope for whole eye transplantation (WET) in patients with devastating vison loss that fails or defies current treatment options. Optic nerve regeneration and reintegration remain the overarching hurdles to WET. However, the realization of WET may indeed be limited by our lack of understanding of the singular immunological features of the eye as pertinent to graft survival and functional vision restoration in the setting of transplantation. RECENT FINDINGS: Like other VCA, such as the hand or face, the eye includes multiple tissues with distinct embryonic lineage and differential antigenicity. The ultimate goal of vision restoration through WET requires optimal immune modulation of the graft for successful optic nerve regeneration. Our team is exploring barriers to our understanding of the immunology of the eye in the context of WET including the role of immune privilege and lymphatic drainage on rejection, as well as the effects ischemia, reperfusion injury and rejection on optic nerve regeneration. SUMMARY: Elucidation of the unique immunological responses in the eye and adnexa after WET will provide foundational clues that will help inform therapies that prevent immune rejection without hindering optic nerve regeneration or reintegration.

Demonstration of technical feasibility and viability of whole eye transplantation in a rodent model.

INTRODUCTION: Whole eye transplantation (WET) holds promise for vision restoration in devastating/disabling visual loss (congenital or traumatic) not amenable to surgical or neuroprosthetic treatment options. The eye includes multiple tissues with distinct embryonic lineage and differential antigenicity. Anatomically and immunologically, the eye is unique due to its avascular (cornea) and highly vascular (retina) components. Our goal was to establish technical feasibility, demonstrate graft viability, and evaluate histologic changes in ocular tissues/adnexae in a novel experimental model of WET that included globe, adnexal, optic nerve (ON), and periorbital soft tissues. METHODS: Outbred Sprague-Dawley rats (n = 5) received heterotopic vascularized WET from donors. Each WET included the entire globe, adnexa, ON, and periorbital soft tissues supplied by the common carotid artery and external jugular vein. Viability and perfusion were confirmed by clinical examination, angiography and magnetic resonance imaging (MRI). Globe, adnexal, and periorbital tissues were analyzed for histopathologic changes, and the ON was examined for neuro-regeneration at study endpoint (30 days) or Banff Grade 3 rejection in the periorbital skin (whichever was earlier). RESULTS: Gross examination confirmed transplant viability and corneal transparency. Average operative duration was 64.0 ±â€¯5.8 min. Average ischemia time was 26.0 ±â€¯4.2 min. MRI revealed loss of globe volume by 36.0 ±â€¯2.8% after transplantation. Histopathology of globe and adnexal tissues showed unique and differential patterns of inflammatory cell infiltration. The ON revealed a neurodegeneration pattern. CONCLUSION: The present study is the first in the literature to establish an experimental model of WET. This model holds significant potential in investigating mechanistic pathways, monitoring strategies or developing management approaches involving ocular viability, immune rejection, and ON regeneration after WET.

The Barcelona Principles: An Agreement on the Use of Human Donated Tissue for Ocular Transplantation, Research, and Future Technologies©.

PREAMBLE: The Barcelona Principles: An Agreement on the use of human donated tissue for ocular transplantation, research, and future technologies (Agreement) is a global bioethical framework (GBF), developed by the eye bank and ophthalmic communities, to inform on the management of altruistic and voluntary donations; their subsequent utility within ophthalmology and research; their retention as a public resource for the shared benefit of all; and their accessibility by waiting recipients.The Agreement is the result of global sector engagement over a 12-month period-led by the Global Alliance of Eye Bank Associations. Its aim is to provide leadership, guidance and recommendations that inform and support sound policy, and sector wide strategic planning and implementation at local, national, regional, and international levels.Inspired by the Declaration of Istanbul on Organ Trafficking and Transplant Tourism, this Agreement affirms the importance of the missions of the United Nations Sustainable Development Goals (Transforming our World: the 2030 Agenda for Sustainable Development); Universal Declaration of Human Rights; World Medical Association's Declaration of Helsinki-Ethical Principles for Medical Research Involving Human Subjects, and their Statement on Organ and Tissue Donation; The Council for International Organizations of Medical Science's International Ethical Guidelines for Health-related Research Involving Humans 2016; and accords with the World Health Organization's 2010 Guiding principles on human cell, tissue, and organ transplantation-WHA63.22.With millions waiting for a corneal transplant at any given moment-and the majority residing in lower resource locations, a significant component of this Agreement promotes equitable allocation systems for waiting recipients, and the development of self-sufficient services. It recognises important instruments, such as the International Council of Ophthalmology 2017 Position Statement: Donation, Processing, Allocation, Advocacy, and Legislation Supporting Human Corneal Tissue for Ocular Transplant; the World Health Organization's Universal Eye Health-Global Action Plan 2014 to 2019, and the mission of the International Agency for the Prevention of Blindness.Future biological innovations/technologies are also addressed within the Agreement, promoting research and development that seek to improve donation utility, reduce burden, and improve therapeutic options for recipients, without ethical compromise.The Agreement has been developed by the Global Alliance of Eye Bank Associations in conjunction with the International Council of Ophthalmology, International Agency for the Prevention of Blindness, The Corneal Society, Asian Eye Bank Association, European Eye Bank Association, Eye Bank Association of America, Eye Bank Association of Australia and New Zealand, Eye Bank Association of India, the Pan American Association of Eye Banks, and in countries and regions without eye bank organizations, their ophthalmic societies-such as the Ophthalmological Society of the West Indies, and the Pacific Eye Care Society.Finally, we endorse the current international consensus that prohibits trafficking and transplant tourism.

Self-organization and progenitor targeting generate stable patterns in planarian regeneration.

During animal regeneration, cells must organize into discrete and functional systems. We show that self-organization, along with patterning cues, govern progenitor behavior in planarian regeneration. Surgical paradigms allowed the manipulation of planarian eye regeneration in predictable locations and numbers, generating alternative stable neuroanatomical states for wild-type animals with multiple functional ectopic eyes. We used animals with multiple ectopic eyes and eye transplantation to demonstrate that broad progenitor specification, combined with self-organization, allows anatomy maintenance during regeneration. We propose a model for regenerative progenitors involving (i) migratory targeting cues, (ii) self-organization into existing or regenerating eyes, and (iii) a broad zone, associated with coarse progenitor specification, in which eyes can be targeted by progenitors. These three properties help explain how tissues can be organized during regeneration.

A New Composite Eyeball-Periorbital Transplantation Model in Humans: An Anatomical Study in Preparation for Eyeball Transplantation.

BACKGROUND: Vascularized composite allotransplantation offers a new hope for restoration of orbital content and perhaps vision. The aim of this study was to introduce a new composite eyeball-periorbital transplantation model in fresh cadavers in preparation for composite eyeball allotransplantation in humans. METHODS: The composite eyeball-periorbital transplantation flap borders included the inferior border, outlined by the infraorbital rim; the medial border, created by the nasal dorsum; the lateral border, created by the lateral orbital rim; and the superior border, created by the superior part of the eyebrow. The pedicle of the flap included the facial artery, superficial temporal artery, and external jugular vein. The skin and subcutaneous tissues of the periorbital region were dissected and the bony tissue was reached. A coronal incision was performed and the frontal lobe of the brain was reached by means of frontal osteotomy. Ophthalmic and oculomotor nerves were also included in the flap. After a "box osteotomy" around the orbit, the dissection was completed. Methylene blue and indocyanine green injection (SPY Elite System) was performed to show the integrity of the vascular territories after facial flap harvest. RESULTS: Adequate venous return was observed within the flap after methylene blue dye injection. Laser-assisted indocyanine green angiography identified a well-defined vascular network within the entire composite eyeball-periorbital transplantation flap. CONCLUSIONS: For the first time, a novel composite eyeball-periorbital transplantation model in human cadavers was introduced. Good perfusion of the flap confirmed the feasibility of composite eyeball-periorbital transplantation in the clinical setting. Although harvesting of the flap is challenging, it introduces a new option for reconstruction of the periorbital region including the eyeball.

Distribution of potential eye and tissue donors within an Australian teaching hospital.

Eye and Tissue donation has the capacity to transform lives, yet the vast majority of potential in-hospital donors are not recognised. Studies which describe the relative importance of specific units or wards in determining the size of the donor pool are limited. The aim of this study was to map the distribution of potential Eye and Tissue donors within the study hospital. A 12-month retrospective analysis of all patient deaths at the study hospital was undertaken. The ability to donate corneal, heart valve, bone and skin tissue was investigated. Patients were classified as potential donors if they met specific age criteria and had an absence of contraindications based on electronic database search. There were 985 deaths during the study period. Deaths occurred under the care of 26 separate clinical units, and within 28 unique wards and treatment spaces. Four hundred and forty nine (45.6%) patients were identified as potential eye or tissue donors. The majority of potential donors occurred in ICU, Emergency and palliative care units. Of the subset of 328 deaths ≤ 70 years, the frequency of potential tissue donors was 55% (n = 181). ED and ICU had significantly higher frequencies of potential donor than other wards (86 and 77%, p < 0.01). The current study has identified the ED, ICU and PCUs are being important sites for potential Eye and Tissue Donors within our hospital. These will provide an important focus for future interventions to improve the rate of eye and tissue donation.

Histological, immunohistochemical and clinical considerations on amniotic membrane transplant for ocular surface reconstruction.

Amniotic membrane (AM) transplantation has been used successfully worldwide in ophthalmology plastic surgery for over 100 years. This review presents the histological and the immunohistochemical features of AM compared to those of the conjunctiva and discusses the techniques of processing and preservation, its mechanism of action in ocular reconstruction, its clinical ophthalmic indications, but also advantages and limitations of grafting with this biomaterial.

Development of national system performance metrics for tissue donation, production, and distribution activity.

Canada's federal, provincial, and territorial governments gave Canadian Blood Services a mandate for organ and tissue donation and transplantation, including system performance, data and analytics. In 2012 Canadian Blood Services facilitated an eye and tissue banking workshop focused on standardized specifications and practices. At the workshop, the Canadian tissue community directed Canadian Blood Services to facilitate the development and implementation of a national data stream and analytics. Prior to this no national data was prospectively collected or collated on tissue donation, production or distribution activity. An eye and tissue data committee was formed with representation from eye and tissue banks in all Canadian jurisdictions. A minimum data set, standardized definitions, a data submission form and a quality assurance process was developed. Training was provided to data personal identified by each eye and tissue bank. Data collection was initiated January 1, 2013; with quarterly data submitted to Canadian Blood Services via excel spreadsheet. Data was submitted by sixteen Canadian eye and tissue banks, located in eight of Canada's thirteen provinces and territories, representing a census of activity. Annual data reports, with trend analysis, are generated and distributed to the tissue community to inform operational strategy and system performance improvement. This report provides an overview of the data process and provides visibility to the Canadian tissue donation, production and distribution activities for 3 years; January 1, 2013 to December 31, 2015.

[Artificial organs]. / Les organes artificiels.

Research has been fighting against organ failure and shortage of donations by supplying artificial organs for many years. With the raise of new technologies, tissue engineering and regenerative medicine, many organs can benefit of an artificial equivalent: thanks to retinal implants some blind people can visualize stimuli, an artificial heart can be proposed in case of cardiac failure while awaiting for a heart transplant, artificial larynx enables laryngectomy patients to an almost normal life, while the diabetic can get a glycemic self-regulation controlled by smartphones with an artificial device. Dialysis devices become portable, as well as the oxygenation systems for terminal respiratory failure. Bright prospects are being explored or might emerge in a near future. However, the retrospective assessment of putative side effects is not yet sufficient. Finally, the cost of these new devices is significant even if the advent of three dimensional printers may reduce it.

Whole-eye transplantation: a look into the past and vision for the future.

Blindness afflicts ~39 million people worldwide. Retinal ganglion cells are unable to regenerate, making this condition irreversible in many cases. Whole-eye transplantation (WET) provides the opportunity to replace diseased retinal ganglion cells, as well as the entire optical system and surrounding facial tissue, if necessary. Recent success in face transplantation demonstrates that this may be a promising treatment for what has been to this time an incurable condition. An animal model for WET must be established to further enhance our knowledge of nerve regeneration, immunosuppression, and technical aspects of surgery. A systematic review of the literature was performed to evaluate studies describing animal models for WET. Only articles in which the eye was completely enucleated and reimplanted were included. Study methods and results were compared. In the majority of published literature, WET can result in recovery of vision in cold-blooded vertebrates. There are a few instances in which mammalian WET models demonstrate survival of the transplanted tissue following neurovascular anastomosis and the ability to maintain brief electroretinogram activity in the new host. In this study we review in cold-blooded vertebrates and mammalian animal models for WET and discuss prospects for future research for translation to human eye transplantation.

Total Human Eye Allotransplantation: Developing Surgical Protocols for Donor and Recipient Procedures.

BACKGROUND: Vascularized composite allotransplantation of the eye is an appealing, novel method for reconstruction of the nonfunctioning eye. The authors' group has established the first orthotopic model for eye transplantation in the rat. With advancements in immunomodulation strategies together with new therapies in neuroregeneration, parallel development of human surgical protocols is vital for ensuring momentum toward eye transplantation in actual patients. METHODS: Cadaveric donor tissue harvest (n = 8) was performed with orbital exenteration, combined open craniotomy, and endonasal approach to ligate the ophthalmic artery with a cuff of paraclival internal carotid artery, for transection of the optic nerve at the optic chiasm and transection of cranial nerves III to VI and the superior ophthalmic vein at the cavernous sinus. Candidate recipient vessels (superficial temporal/internal maxillary/facial artery and superficial temporal/facial vein) were exposed. Vein grafts were required for all anastomoses. Donor tissue was secured in recipient orbits followed by sequential venous and arterial anastomoses and nerve coaptation. Pedicle lengths and calibers were measured. All steps were timed, photographed, video recorded, and critically analyzed after each operative session. RESULTS: The technical feasibility of cadaveric donor procurement and transplantation to cadaveric recipient was established. Mean measurements included optic nerve length (39 mm) and caliber (5 mm), donor artery length (33 mm) and caliber (3 mm), and superior ophthalmic vein length (15 mm) and caliber (0.5 mm). Recipient superficial temporal, internal maxillary artery, and facial artery calibers were 0.8, 2, and 2 mm, respectively; and superior temporal and facial vein calibers were 0.8 and 2.5 mm, respectively. CONCLUSION: This surgical protocol serves as a benchmark for optimization of technique, large-animal model development, and ultimately potentiating the possibility of vision restoration transplantation surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

Clinical Considerations for Vascularized Composite Allotransplantation of the Eye.

Vascularized composite allotransplantation represents a potential shift in approaches to reconstruction of complex defects resulting from congenital differences as well as trauma and other acquired pathology. Given the highly specialized function of the eye and its unique anatomical components, vascularized composite allotransplantation of the eye is an appealing method for restoration, replacement, and reconstruction of the nonfunctioning eye. Herein, we describe conventional treatments for eye restoration and their shortcomings as well as recent research and events that have brought eye transplantation closer to a potential clinical reality. In this article, we outline some potential considerations in patient selection, donor facial tissue procurement, eye tissue implantation, surgical procedure, and potential for functional outcomes.

Estimation of the potential eye and tissue donor pool in an Australian emergency department.

OBJECTIVE: EDs have long been considered a potential source of eye and tissue donors, but no specific evidence to support this was identified in the Australian setting. The present study aims to bridge that knowledge gap, by analysing medical and social histories of those who have died over a 5 year period so as to determine donation eligibility in this population. METHODS: A retrospective audit was undertaken of all patients who died within the Royal Melbourne Hospital ED between 2010 and 2014. ED records, pharmacy records and electronic medical histories were audited for the presence of eye and tissue donation exclusion criteria and the distribution of these criteria within the target population. RESULTS: Over the 5 year period, of 326 deaths that occurred in the ED, one third was suitable for eye donation (n = 106) and one in seven (n = 45) for tissue donation. Of the age appropriate patients, five criteria were identified that excluded up to 85% of the population not eligible to donate. These were: haematological malignancies, neurodegenerative conditions, non-haematological malignancies, chronic renal failure and eye disease. CONCLUSION: The present study has identified a large pool of potential eye and tissue donors; a pool mostly unrecognised by emergency clinicians. An extensive list of exclusion criteria restricts donor potential. However, the present study has identified that only five fundamentally limit donation in the ED population. Utilisation of this knowledge will allow for the development of clinical triggers that will improve identification, and increase realisation, of potential donors.

Ethical Considerations of Whole-Eye Transplantation.

Whole eye transplantation (WET) remains experimental. Long presumed impossible, recent scientific advances regarding WET suggest that it may become a clinical reality. However, the ethical implications of WET as an experimental therapeutic strategy remain largely unexplored. This article evaluates the ethical considerations surrounding WET as an emerging experimental treatment for vision loss. A thorough review of published literature pertaining to WET was performed; ethical issues were identified during review of the articles.