Advantages of subretinal delivery by robotic assistance over a manual approach

Purpose: Robotics provides high positional stability as well as micrometer precision and accuracy in XYZ. It also removes any time constraint on drug delivery within the subretinal space. Hence, the delivery procedure can be analyzed and optimized using appropriate imaging techniques and its performance compared to manual surgery.Materials and Methods: Freshly harvested porcine eyes were used for the initial studies. A standard pars plana vitrectomywith IOP control was performed under microscopic visualization through a Zeiss Rescan 700. Subsequently, subretinal injection using a 41G Teflon needle, was executed with or without the Preceyes Surgical System (PSS). The following parameters were recorded: absence of a Bruch’s membrane breech, initiation success and duration to subretinal bleb creation. Surgical iOCT and microscopic recording where analyzed and categorized after completion of the surgery. Surgical success was defined as a creation of a subretinal bleb confirmed by intraoperative oct, while avoiding reflux.Results: No breech of Bruch’s membrane was observed using either manual or robotic assistance. While static positioning was possible manually in the subretinal space, repeated contact with Bruch’s was observed due to physiologic hand tremor. There was no motion while using the PSS. Surgical success was achievedin 80% of PSS assisted surgeries (blebs creation in 100%, with leakage in 20% at the time of retraction). With manual surgery, leakage was observed in all cases, in only 40% of cases could a bleb be successfully created. Leakage was observed at all stages of bleb initiation, injection and retraction of the needle. Time involved in bleb generation was longer while using the PSS which may have bearing on the success.Conclusions: Robotics allows for a more controlled access to the subretinal space, minimizes the risk of reflux, during the injection process or on retraction of the needle. PSS also allowed for realtime use of an iOCT to guide the injection process.