Total Human Eye Allotransplantation (THEA): Preclincal Cadaveric Studies

Abstract

Purpose : It is estimated that approximately 40 million suffer from blindness globally. Whole eye transplantation offers the opportunity to provide viable retinal ganglion cells and an entire optical system to recipients with vision loss. Our 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 in ensuring momentum towards eye transplantation in patients.

Methods : Preserved injected human cadaveric heads (n=8) underwent donor and recipient procedures. Bilateral transplants were performed between two cadavers in each surgical session, for a total of 4 transplants between 2 cadavers. A globe and periorbita model was adopted. Donor procurement required orbital exenteration with combined endonasal and transcranial approach to decompress the orbital apex. Transection of cranial nerves II-VI and superior ophthalmic vein was performed at the cavernous sinus transcranially and the ophthalmic artery with carotid artery stem was ligated in the paraclival space to deliver the donor specimen. Candidate recipient vessels (superficial temporal, internal maxillary and facial artery and superficial temporal and facial vein) were exposed. All required vein grafting. Donor tissue was secured in recipient orbits followed by sequential arterial and venous anastomoses and nerve coaptation with standard microsurgical techniques. Pedicle lengths and calibers were measured. All steps were timed, photographed, video recorded and analyzed after each operative session.

Results : Technical feasibility of cadaveric donor procurement and transplantation to cadaveric recipient was established. Mean donor ophthalmic artery pedicle length and caliber were 13.5 and 1mm but with a stem of paraclival internal carotid artery were 33 and 2mm. Mean optic nerve was 25mm from orbital apex to annulus of Zinn and 14 mm from annulus of Zinn to optic chiasm. Cranial nerves III-VI had mobile pedicle lengths of 10-14mm. Candidate recipient vessels required vein grafting.

Conclusions : 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.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.