A custom virtual reality training solution for ophthalmologic surgical clinical trials

Abstract

We present a summary of the development and clinical use of two custom designed high-fidelity virtual-reality simulator training platforms. This simulator development program began in 2016 to support the phase III clinical trial Archway (ClinicalTrials.gov identifier, NCT03677934) intended to evaluate the Port Delivery System (PDS) developed by Genentech Inc. and has also been used to support additional clinical trials. The two simulators address two specific ophthalmic surgical procedures required for the successful use of PDS and provide state-of-the-art physical simulation models and graphics. The simulators incorporate customized active haptic feedback input devices that approximate different hand pieces including a custom hand piece specifically designed for PDS implantation. We further describe the specific challenges of the procedure and the development of corresponding training strategies realized within the simulation platform.

Conflict of interest statement

The custom simulator development described was a collaborative effort of Genentech Inc. and VRmagic GmbH. All authors are employees of either VRmagic GmbH or Genentech Inc.

Figures

Fig. 1

The implantation procedure requires the surgeon to perform a dissection of the conjunctiva as well as the attached Tenon’s capsule (a) and then mark the end points of the scleral dissection on the sclera (b). This is necessary as the scleral dissection (c) must have a length of exactly 3.5 mm with little margin for error. Afterwards, the well perfused pars plana tissue underlying the sclera needs to be coagulated (d) to ensure that the following pars plana incision (e) does not result in vitreous hemorrhage. Finally, using a special implantation tool, the Port Delivery System implant is inserted (f) into the globe and released from the tool (g). In a final step, the conjunctiva and Tenon’s capsule are closed and sutured (h)

Fig. 2

The pictures to the left and in the middle illustrate the concept of the refill-exchange procedure. A correct execution requires the full penetration of the special vented refill needle into the self-sealing septum of the PDS implant. This can only be achieved if the entry point of the needle is centralized within the septum surface and the needle is perpendicularly aligned with the implant. The picture to the right shows a simulator screenshot and illustrates the use of abstract guidance elements to help the user understand the geometric challenges of the procedure

Fig. 3

The simulator platform for the implant insertion procedure (left picture) approximates a setup in which the user sits in an OR environment and performs surgery on the virtual patient from a frontal position. Only about one quadrant of the virtual patient’s head is actually realized as a physical model, roughly modeling the part from the brow ridge to the top, which is necessary as a hand rest for the user. The simulator platform for the refill-exchange procedure (right picture) enables the user to stand next to the virtual patient who is positioned sitting in an inclined ophthalmic chair

Fig. 4

The pictures above show graphical renderings from all four training modules of the implant insertion simulator. All relevant physical effects are simulated in real time including the fluid dynamics of blood, supra choroidal fluids, and vitreous, the elastic instrument interaction with the sclera tissue, the ablation effects of the laser, and the dissection of sclera and pars plana tissue. The pictures also illustrate some of the VR guidance elements that instruct the user during training. During scleral dissection, a heads-up display (HUD) shows a profile illustrating the cut depth and length (top-left picture). During pars plana ablation, a heat map can be shown either in the periphery of the field-of-view (top-right picture) or directly over the pars plana tissue (see Fig. 5). During pars plana incision, a cross section of the supra-temporal eye quadrant illustrates the penetration depth and angle of the slit knife and its proximity to intra-ocular structures (bottom-left picture)

Fig. 5

A homogeneous application of the laser to the pars plana tissue is paramount and thus the user needs to understand the visual cues that indicate the current state of ablation. The pictures above show actual renderings from the implant insertion simulator that illustrate how the laser ablation changes the appearance of the pars plana tissue. The first few laser shots provide distinct localized deformation and discoloration of the tissue. Further ablation results in the expression of a fine granular texture as well as further darkening of the tissue. Eventually, perforation of the pars plana tissue will occur and result in percolation of thick vitreous or a prolapse of liquefied vitreous. The VR simulation is sufficiently accurate to compute a heat map illustrating the degree of ablation with a high-spatial resolution and thus allows the user to train its perception of the state of ablation and ensure a homogeneous application