Force and Velocity Based Puncture Detection in Robot Assisted Retinal Vein Cannulation: In-Vivo Study.

OBJECTIVE: Retinal vein cannulation is a technically demanding surgical procedure and its feasibility may rely on using advanced surgical robots equipped with force-sensing microneedles. Reliable detection of the moment of venous puncture is important, to either alert or prevent the clinician from double puncturing the vessel and damaging the retinal surface beneath. This paper reports the first in-vivo retinal vein cannulation trial on rabbit eyes, using sensorized metal needles, and investigates puncture detection. METHODS: We utilized total of four indices including two previously demonstrated ones and two new indices, based on the velocity and force of the needle tip and the correlation between the needle-tissue and tool-sclera interaction forces. We also studied the effect of detection timespan on the performance of detecting actual punctures. RESULTS: The new indices, when used in conjunction with the previous algorithm, improved the detection rate form 75% to 92%, but slightly increased the number of false detections from 37 to 43. Increasing the detection window improved the detection performance, at the cost of adding to the delay. CONCLUSION: The current algorithm can supplement the surgeons' visual feedback and surgical judgment. To achieve automatic puncture detection, more measurements and further analysis are required. Subsequent in-vivo studies in other animals, such as pigs with their more human like eye anatomy, are required, before clinical trials. SIGNIFICANCE: The study provides promising results and the criteria developed may serve as guidelines for further investigation into puncture detection in in-vivo retinal vein cannulation.

Chorioretinal Anastomosis for Central Retinal Vein Occlusion: A Review of Its Development, Technique, Complications, and Role in Management.

Treatments for central retinal vein occlusion (CRVO) have improved dramatically with the advent of intravitreal agents aimed at blocking the effects of the dominant hypoxia-induced upreglulated cytokine, which is vascular endothelial growth factor (VEGF). This cytokine breaks down the capillary endothelial barriers and is a major component of the macular edema in this condition. These treatments although impressive only address some of the sequelae of CRVO and have no effect on the underlying cause which is an obstruction to venous outflow leading to retinal blood flow stagnation and an elevation of the retinal central venous pressure (CVP). The creation of a laser-induced chorioretinal anastomosis (L-CRA) between the obstructed high pressure retinal venous circulation and the unobstructed low pressure choroidal venous circulation is a means addressing the causal pathology. The L-CRA will help lower the elevated CVP, which has been up until now an unaddressed component of the macular edema in this condition.This article reviews the preclinical and clinical development of the L-CRA and the results of the studies into its effect on the natural history of CRVO. It now can be used in combination with existing anti-VEGF treatments with the intravitreal agents addressing the component of the CRVO-induced macular edema due to the cytokine dysregulation, and the L-CRA addressing the component due to the elevated CVP and retinal venous stagnation. Improvements in laser technology have led to higher success rates in L-CRA creation and potential complications are now minimized and better controlled. The combination of L-CRA with intravitreal anti-VEGF agents offers the potential of a permanent cure with a significant reduction in the burden of therapy and improved visual outcomes in this condition.

Evaluation of a Force-Sensing Handheld Robot for Assisted Retinal Vein Cannulation.

Approximately 16.4 million people are affected by retinal vein occlusion (RVO) resulting from hypercoagulability, low blood flow or thrombosis in the central or the branched retinal veins. Most common current treatments for RVO aim to limit the damage. In recent years, an experimental procedure, retinal vein cannulation (RVC) has been studied in animal models as well as human eye models. RVC is a procedure for targeted delivery of a therapeutic agent into the occluded retinal vein for dissolving the thrombi. Although effective treatment has been demonstrated via RVC, performing this procedure manually still remains at the limits of human skills. RVC requires to precisely insert a thin cannula into a delicate thin retinal vein, and to maintain it inside the vein throughout the infusion. The needle-vein interaction forces are too small to sense even by an expert surgeon. In this work, we present an evaluation study of a handheld robotic assistant with a force-sensing microneedle for RVC. The system actively cancels hand tremor, detects venous puncture based on detected tool-tissue forces, and stabilizes the needle after venous puncture for reduced trauma and prolonged infusion. Experiments are performed cannulating the vasculature in fertilized chicken eggs. Results show 100% success in venous puncture detection and significantly reduced cannula position drift via the stabilization aid of the robotic system.

In-Human Robot-Assisted Retinal Vein Cannulation, A World First.

Retinal Vein Occlusion (RVO) is a blinding disease caused by one or more occluded retinal veins. Current treatment methods only focus on symptom mitigation rather than targeting a solution for the root cause of the disorder. Retinal vein cannulation is an experimental eye surgical procedure which could potentially cure RVO. Its goal is to dissolve the occlusion by injecting an anticoagulant directly into the blocked vein. Given the scale and the fragility of retinal veins on one end and surgeons' limited positioning precision on the other, performing this procedure manually is considered to be too risky. The authors have been developing robotic devices and instruments to assist surgeons in performing this therapy in a safe and successful manner. This work reports on the clinical translation of the technology, resulting in the world-first in-human robot-assisted retinal vein cannulation. Four RVO patients have been treated with the technology in the context of a phase I clinical trial. The results show that it is technically feasible to safely inject an anticoagulant into a [Formula: see text]-thick retinal vein of an RVO patient for a period of 10 min with the aid of the presented robotic technology and instrumentation.

Ocular Hypertension/Glaucoma in Minipigs: Episcleral Veins Cauterization and Microbead Occlusion Methods.

Two methods to induce elevation of the intraocular pressure (experimental glaucoma) are described in the present chapter. The first method is based on increasing the post-trabecular resistance to aqueous outflow by cauterizing the episcleral veins (EVC). This method allows the observation of ultrastructural changes in the trabecular meshwork (TM) without interfering with any structure within the eye such as TM, ciliary body, and/or the Retina. The second method is the multiple injection of microbeads into the anterior chamber, as a pre and intra-trabecular method that induce secondary effects on the TM cells. Both methods lead to an increase in IOP.

Towards Robot-Assisted Retinal Vein Cannulation: A Motorized Force-Sensing Microneedle Integrated with a Handheld Micromanipulator †.

Retinal vein cannulation is a technically demanding surgical procedure where therapeutic agents are injected into the retinal veins to treat occlusions. The clinical feasibility of this approach has been largely limited by the technical challenges associated with performing the procedure. Among the challenges to successful vein cannulation are identifying the moment of venous puncture, achieving cannulation of the micro-vessel, and maintaining cannulation throughout drug delivery. Recent advances in medical robotics and sensing of tool-tissue interaction forces have the potential to address each of these challenges as well as to prevent tissue trauma, minimize complications, diminish surgeon effort, and ultimately promote successful retinal vein cannulation. In this paper, we develop an assistive system combining a handheld micromanipulator, called "Micron", with a force-sensing microneedle. Using this system, we examine two distinct methods of precisely detecting the instant of venous puncture. This is based on measured tool-tissue interaction forces and also the tracked position of the needle tip. In addition to the existing tremor canceling function of Micron, a new control method is implemented to actively compensate unintended movements of the operator, and to keep the cannulation device securely inside the vein following cannulation. To demonstrate the capabilities and performance of our uniquely upgraded system, we present a multi-user artificial phantom study with subjects from three different surgical skill levels. Results show that our puncture detection algorithm, when combined with the active positive holding feature enables sustained cannulation which is most evident in smaller veins. Notable is that the active holding function significantly attenuates tool motion in the vein, thereby reduces the trauma during cannulation.

[Treatment of Retinal Vein Occlusion - Is There Still a Role for Vitreoretinal Surgery?] / Behandlung des retinalen Venenverschlusses ­ Welche Rolle spielt die Vitrektomie heute noch?

Surgical manoeuvres for the treatment of retinal vein occlusion peaked at the turn of the century. The first overwhelming reports could not be confirmed in prospective studies. Furthermore, the functional success was never comparable to intravitreal drug therapy, and the manoeuvres are no longer used in clinical routine. The procedures, the surgical theory and the criticism on vitrectomy, radial optic neurotomy (RON), retinal endovascular fibrinolysis (REVL) and arteriovenous dissection (AVD) will be discussed in this paper. Surgical manoeuvres for the treatment of retinal vein occlusion had a peak by the end of the last and the beginning of the present century. The first overwhelming reports could not be confirmed in prospective studies. Furthermore, the functional success was never comparable to the intravitreal drug therapy and the manoeuvres are no longer used in clinical routine. The procedures, the surgical theory and the criticism on vitrectomy, radial optic neurotomy (RON), retinal endovascular fibrinolysis (REVL), and arteriovenous dissection (AVD) will be discussed in this paper.

Robot-assisted retinal vein cannulation in an in vivo porcine retinal vein occlusion model.

PURPOSE: To evaluate the feasibility of robot-assisted retinal vein cannulation for retinal vein occlusion. METHODS: Prospective experimental study performed in in vivo porcine eyes. A standard three port pars plana vitrectomy was followed by laser-induced branch retinal vein occlusion. Consequently, a retinal vein cannulation with the help of a surgical robot and a microneedle was performed. Complete success was defined as a stable intravenous position of the needle tip confirmed by blood washout for at least 3 min. Secondary outcomes were the occurrence of intra-operative complications and technical failures. RESULTS: Cannulation was successful in 15 of 18 eyes with a complete success rate (duration of infusion of more than 3 min) of 73% after exclusion of two eyes from analysis due to failure in establishing a blood clot. There were no technical failures regarding the robotic device. The intravessel injections of ocriplasmin in two of two eyes led to a clot dissolution. In a subset of five eyes, a second cannulation attempt at the border of the optic disc resulted in a stable intravessel position and infusion during 362 (±138) seconds. CONCLUSION: Robot-assisted retinal vein cannulation with prolonged infusion time is technically feasible. Human experiments are required to analyse the clinical benefit of this new therapy.

TECHNIQUE OF LASER CHORIORETINAL ANASTOMOSIS CREATION IN CENTRAL RETINAL VEIN OCCLUSION AND SUCCESS RATE WITH A NEW PHOTOCOAGULATOR SYSTEM.

PURPOSE: To evaluate the success rate of laser chorioretinal anastomosis (L-CRA) creation with a new laser photocoagulator system capable of 5 watts (W) power in patients with central retinal vein occlusion (CRVO). METHODS: Patients with a treatment-naive CRVO were enrolled as part of an ongoing trial combining L-CRAs with anti-vascular endothelial growth factor treatment. RESULTS: Thirty-three patients were treated with an L-CRA developing in 29 (88%). Mean power was 2.7 W and mean time for development was 1.8 months. Each patient had two potential sites created. Eighteen patients developed 2 L-CRAs and the remaining 11 patients, one each. Of the 66 potential sites, successful L-CRAs developed at 47 sites (71%). Additional Nd:YAG laser applications were used in 39% of sites. Mean follow-up was 23 months and no significant complications were seen. CONCLUSION: An L-CRA as a means of permanently bypassing the obstruction to venous outflow in CRVO may become more relevant as not all patients respond well to intravitreal therapy. The limitation to this technique in the past has been lack of availability of a laser system with the power necessary to create the L-CRA. The success rate with the new system has improved to 88% representing a significant improvement over our original success rate of 33%.

Intraocular metallic foreign body causing branch retinal vein occlusion.

We report a case of a 40-year-old man with post-traumatic cataract and an intraocular metallic foreign body (IOFB) lying on the retinal surface causing a superotemporal branch retinal vein occlusion. The case was managed using lens aspiration with pars plana vitrectomy and IOFB removal. We only found two previous reports of such a foreign body causing a vascular occlusion. The possibility of a vascular occlusion occurring due to a foreign body within or close to the optic disc is highlighted.

Robot-assisted retinal vein cannulation with force-based puncture detection: Micron vs. the steady-hand eye robot.

Retinal vein cannulation is a demanding procedure where therapeutic agents are injected into occluded retina veins. The feasibility of this treatment is limited due to challenges in identifying the moment of venous puncture, achieving cannulation and maintaining it throughout the drug delivery period. In this study, we integrate a force-sensing microneedle with two distinct robotic systems: the handheld micromanipulator Micron, and the cooperatively controlled Steady-Hand Eye Robot (SHER). The sensed tool-to-tissue interaction forces are used to detect venous puncture and extend the robots' standard control schemes with a new position holding mode (PHM) that assists the operator hold the needle position fixed and maintain cannulation for a longer time with less trauma on the vasculature. We evaluate the resulting systems comparatively in a dry phantom, stretched vinyl membranes. Results have shown that modulating the admittance control gain of SHER alone is not a very effective solution for preventing the undesired tool motion after puncture. However, after using puncture detection and PHM the deviation from the puncture point is significantly reduced, by 65% with Micron, and by 95% with SHER representing a potential advantage over freehand for both.

In Vivo Retinal Vein Bypass Surgery in a Porcine Model.

PURPOSE: To evaluate the feasibility of retinal vein bypass surgery for induced branch retinal-vein occlusion (BRVO) in the living porcine eye. METHODS: Fifteen minipigs were used in the study. Seven days before vascular surgery, hyaluronidase and plasmin were intravitreally injected for induction of posterior vitreous detachment. Aspirin and warfarin were oral administered daily starting 5 d prior to vascular surgery for anti-coagulation. The minipigs were anethetized with an intraperitoneal injection of 300 mg/kg chloral hydrate for intravitreal injection procedure and vascular surgery. Temporary keratoprosthesis vitrectomy was performed, and intraoperative video fluorescein angiography (VFA) was possible. The central and posterior vitreous was removed together with the posterior hyaloid membrane to facilitate vascular maneuvers. BRVO was induced by bipolar diathermy on the vein at the main vein's first branching. Polyimide tubes (50.8-µm internal diameter and 7.6-µm wall thickness) were used as artificial vessels. Vascular manipulation was performed in a bimanual manner. Both end of a prepared tubing was inserted into venous lumen by puncturing and catheterization, and the vein bypass bridging the occlusion was created. Then, the patency of the bypass graft was assessed by intraoperative VFA. RESULTS: The retinal vein bypass surgery was surgically accomplished in 33% (5/15) of the eyes, and the immediate graft patency was confirmed by intraoperative VFA only in one eye. We observed and recorded fluorescein flow from the branch vein to the main vein through the bypass graft which bridging the occlusive vein segment. CONCLUSIONS: We demonstrated the feasibility of retinal vein bypass for induced BRVO in the living porcine eye, and the immediate graft patency was successfully evaluated by intraoperative VFA. Despite the potential, there are still some significant hurdles in vivo retinal vein bypass surgery, and modification of both surgical instruments and maneuvers is needed for further study.

Macular hole formation following intravitreal injection of ranibizumab for branch retinal vein occlusion: a case report.

BACKGROUND: Macular hole formation after anti-vascular endothelial growth factor therapy is a rare complication. We report macular hole formation after intravitreal ranibizumab injection for branch retinal vein occlusion. CASE PRESENTATION: A 63-year-old Asian male was treated with intravitreal ranibizumab injection for chronic macular edema with branch retinal vein occlusion in his right eye. Before treatment, best-corrected visual acuity in his right eye was 20/200. Nine days after injection, a full thickness macular hole developed with reduction of macular edema. After pars plana vitrectomy combined with cataract surgery, the macular hole was successfully closed, and the best-corrected visual acuity in his right eye improved to 20/40. CONCLUSION: The possibility of an infrequent complication like macular hole should be considered for intravitreal ranibizumab for macular edema with branch retinal vein occlusion.

Quantitative assessment of manual and robotic microcannulation for eye surgery using new eye model.

BACKGROUND: Microcannulation, a surgical procedure for the eye that requires drug injection into a 60-90 µm retinal vein, is difficult to perform manually. Robotic assistance has been proposed; however, its effectiveness in comparison to manual operation has not been quantified. METHODS: An eye model has been developed to quantify the performance of manual and robotic microcannulation. The eye model, which is implemented with a force sensor and microchannels, also simulates the mechanical constraints of the instrument's movement. Ten subjects performed microcannulation using the model, with and without robotic assistance. RESULTS: The results showed that the robotic assistance was useful for motion stability when the drug was injected, whereas its positioning accuracy offered no advantage. CONCLUSIONS: An eye model was used to quantitatively assess the robotic microcannulation performance in comparison to manual operation. This approach could be valid for a better evaluation of surgical robotic assistance.