Three dimensional microscopy of ocular tissues using full-field OCT: application to transplantation of tissues and cells for eye diseases – MicroEye

Over the past decade, there has been significant development of noninvasive optical imaging techniques, capable of providing in-depth images of biological tissue without slicing (i.e. «optical biopsy«). These new high resolution imaging tools intend to improve diagnosis and resection procedures. Full-field optical coherence tomography (FF-OCT) offers 3D micrometric resolution over the whole corneal or retinal thickness, producing images similar to histology, but on fresh, whole tissue specimen. It combines attributes of confocal and OCT techniques (both commonly used in ophthalmology practice) to provide both high resolution «en face« and cross sectional views in a single instrument. Studies have shown that FFOCT imaging reveals corneal conditions that are currently difficult to identify in eye banks (eg keratoconus, refractive surgery), allows quantification of cells and cell layers in artificial cornea, and gives unprecedented views of retinal structures and lens fibers.

High resolution non-invasive FFOCT imaging of ocular tissues is expected to 1: allow assessment of each cell layer of donor corneas leading to improved donor to recipient matching and improved graft success rates; 2: allow evaluation over time of bio-engineered corneas and assess suitability for transplantation; 3: give retinal surgeons crucial, timely information about ablated tissues; 4: contribute to basic science knowledge of ocular tissue structures and pathologies. Adoption of the technology by eye banks and surgeons presents a significant market for the associated industrial partner.

«It is foreseen that the project will potentially significantly modify and improve current clinical practice. FFOCT is expected to replace current quality control techniques for preoperative corneal graft assessment. The intrinsic digital nature of FFOCT images is already compatible with telemedicine approaches and intraoperative procedures. High-resolution 3D images of surgically removed tissues paves the way for better understanding of the surgical gesture and further advanced clinical study.
«

Publication accepted 2014 Current Eye Research. 3 publications on FFOCT imaging of ocular tissues in 2004, 2005 by members of the MicroEye research team. Patents on FFOCT technology registered to LLTech SAS. Intent to publish and present new results over the course of the project.

The MicroEye project aims to transfer to the ophthalmology practice the innovative technique of full-field optical coherence tomography (FF-OCT), a breakthrough technology enabling nondestructive histology on fresh, unstained tissues. We hypothesize that the examination of ophthalmic tissue using FF-OCT will represent a major and significant improvement of clinical processes in the field. A research institute (The Vision Institute) and two health institutions (CIC 503 at the CHNO Quinze-Vingts Hospital and Etablissement Français du Sang) collaborate in this study. Three applications are envisioned: preoperative examination of grafts and amniotic membranes for corneal surgery (Task 1); evaluation of bioengineered tissues (Task 2); and analysis of human ocular tissues extracted during surgery (Task 3).

Task 1: Currently, preoperative evaluation of tissue grafts (cornea and amniotic membranes) is very limited, and the extent to which their histological characteristics influence the long-term outcome of the graft (aside from endothelial counts) remains unknown. With the collaboration of the Etablissement Français du Sang, we will thoroughly evaluate the 3D structure of corneal and amniotic membrane grafts using FF-OCT, in conditions as close as possible to the current workflow, and at the same time evaluate receiver corneas. This will provide us with a catalog of corneal optical histopathology. We expect that preoperative FF-OCT will become a standard procedure for eye banks, and that novel quality criteria will emerge from this study.

Task 2: Corneal surgery has been a pioneering area for bioengineering, with the development of cell cultures of the ocular surface and the development of artificial corneas. Here, we will develop a sample analysis approach similar to task 1 yet upstream of future clinical applications. At the Vision Institute, we will use FF-OCT to evaluate the optical characteristics of bioengineered tissue, namely cultured limbal cells and artificial cornea. FF-OCT and conventional evaluation will be done in parallel. A specific goal will be to characterize in the living tissue the cell colonization of artificial corneas.

Task 3: Retinal surgery implicates the dissection of delicate tissues that are barely visible to the naked eye. FF-OCT could therefore be of considerable help to identify the structure ablated by the surgeon, and in particular determine if adjacent structures have been damaged. Here, we plan to use FF-OCT for the examination of fresh tissue fragments extracted during surgery, primarily the internal limiting membrane, in order in particular to identify if neuronal elements are present which could account for postoperative retinal damage. Analysis of vitreous and lens fragments will be conducted as well.

This project will be an important step toward the first application of high-resolution noninvasive microscopy to ophthalmological practice. In return, the scientific body of knowledge would benefit from this innovative approach since it provides a unique view of very delicate structures. This will indeed give an opportunity to better characterize their 3D structure, which is tedious by conventional methods; moreover, ocular tissues in general are very sensitive to post-mortem decay. The partners already have experience of the application of FF-OCT to corneal and retinal tissues, including several years of collaboration with the inventors and then manufacturers of devices, and the geographical proximity of the different sites of the research (including the manufacturer) will ensure optimal interaction between participants.