Four-dimensional microscope-integrated optical coherence tomography (4D MIOCT) guidance in subretinal surgery

Abstract

Purpose : Subretinal (SR) delivery of stem cells and gene therapy vectors have become increasingly promising treatment options. The surgical techniques and visualization are currently evolving. We investigate the utility of 4-dimensional (volumes over time) microscope-integrated optical coherence tomography (4D MIOCT) to guide such SR maneuvers.

Methods : Our swept-source 4D MIOCT images live surgery at up to 10 volumes/second and displays the data through the microscope oculars in near real time using stereoscopic heads-up display. The surgeon controls the volumetric rendering perspective using a foot pedal. In freshly enucleated porcine eyes, we imaged ex-vivo surgical maneuvers including: 1) SR injection of fluid, 2) SR injection of retinal pigment epithelium (RPE) cell suspension, 3) retinotomy creation and 4) SR insertion of polyester (PET) membranes with an RPE cell monolayer.

Results : High quality 4D MIOCT images were visible to the surgeons while performing the 4 maneuvers. Surgeons monitored the extent of the induced retinal detachment (bleb) and assessed the need for further injection with 4D MIOCT images. 4D MIOCT visualization was essential to guide the cannula tip in the SR space and to identify efflux of RPE cells into the vitreous cavity. There was clear visualization of retinotomy scissors in the SR space, their configuration (open/closed) and position with respect to native RPE. Interactions between PET, retina and RPE were not detectable on the conventional microscope view but obvious with 4D MIOCT (Figure 1). 4D MIOCT views allowed adjustment by the surgeon to avoid complications such as scissors touching RPE, or PET-related retinal deformation.

Conclusions : 4D MIOCT is useful for continuous monitoring of model SR surgery maneuvers. In performing specific SR maneuvers, 4D MIOCT-guidance is a useful addition to the conventional microscope view that may help avoid technique-related complications. 4D MIOCT can contribute to the advancement of SR delivery of therapies under development.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Figure 1: Conventional microscope view (A) with simultaneous 4D MIOCT video excerpts (B: volume, C: B-scan) show PET membrane (green arrow) with RPE cells (A,B: tan color) heaped up (A-C: white arrow) before insertion. Vessel pattern is noticeable beneath PET (A,B). Tip of PET is bent on the surface of retina, pressing against and lifting up retina (B,C: blue arrow, not appreciated in A).