Surgical macular dynamics visualized with the intraoperative OCT in a monkey model for RPE replacement

Session Details

Session Title: Free Paper Session 13: Vitreoretinal Surgery IV

Session Date/Time: Friday 08/09/2017 | 14:30-16:00

Paper Time: 14:54

Venue: Room 117

First Author: : G.Tan SINGAPORE

Co Author(s): :    E. Wong   Z. Liu   T. Ilmanrinen   V. Barathi   H. Skottman   B. Stanzel              

Abstract Details

Purpose:

The macula is an attractive target for cell and gene therapies. However, surgical protocols and an understating for associated iatrogenic complications are largely unknown. Here we visualize several implantation protocols with intraoperative optical coherence tomography (iOCT) in a monkey model for retinal pigment epithelium (RPE) replacement with monolayer grafts.

Setting:

In-vivo Animal study

Methods:

Human embryonic stem cell derived RPE were transplanted on translucent cell carriers. Fourteen eyes of monkeys (n= 14) underwent vitrectomy with removal of posterior cortical vitreous. Several modes to create a bleb retinal detachment (bRD) with subretinal BSS injection near the fovea were explored, and included 1) machine- or syringe- based injection, 2) BSS, Air or PFC tamponade, 3) Calcium-free BSS intravitreal infusion for 20 minutes before creating bRD. A retinotomy was created to allow subretinal access. The RPE under the bRD was removed surgically . The RPE monolayer transplant was maneuvered into the subretinal space using custom instrumentation. A fluid air exchange flattened the bRD. All surgical steps were monitored and/or guided with the iOCT. The primary outcome measure was foveal integrity after bRD, secondary outcomes were subfoveal placement of the RPE graft and safety.

Results:

All key surgical steps could be imaged with iOCT. The initial subretinal BSS injection was either from a superotemporal or inferonasal location at the temporal vascular arcades or about 1 disc diameter (DD) from temporal to the macula at IOP set to 5mmHg. In most of these maneuvers (12/14) the subretinal fluid wave “stopped” at the fovea. With the iOCT we were able to distinguish formation of full thickness micro-macular hole (about 10um diameter), BSS-induced cystoid macular edema with or without foveal de-roofing and complete foveal detachment. A combination of starting the fluid wave from 2DD inferonasal to the fovea under PFC resulted in the most controllable detachment of neurosensory retina. Calcium free BSS infusion resulted in a macular hole and massive lens opacification thus compromising safety of the procedure. The iOCT was critical in identifying the location of the implant across opaque retina and confirming subfoveal placement. iOCT controlled visualization of subretinal fluid drainage after fluid air exchange greatly facilitated complete retinal reattachment and confirmed absence of implant movements during this maneuver.

Conclusions:

The iOCT was essential in visualization of surgical sub-macular dynamics for RPE replacement strategies. The (monkey) fovea appears very vulnerable to surgical maneuvers, with anatomical disruption that may only be apparent on iOct. Further work is necessary to minimize iatrogenic damage for subfoveal RPE monolayer transplants.

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