Cooperative robot assistant for vitreoretinal microsurgery: development of the RVRMS and feasibility studies in an animal model.

PURPOSE: The purpose of the study was to describe the development of a robotic aided surgical system named RVRMS (robotic vitreous retinal microsurgery system) and to evaluate the capability for using it to perform vitreoretinal surgery. METHODS: The RVRMS was designed and built to include the key components of two independent arms. End-effectors of each arm fix various surgical instruments and perform intraocular manipulation. To evaluate properly the RVRMS, robot-assisted 23-gauge surgical tasks including endolaser for retinal photocoagulation, pars plana vitrectomy (PPV), retinal foreign body removal and retinal vascular cannulation were performed in two different sizes of an animal model. Endolaser was performed in the eye of a living Irish rabbit and the other tasks were done in a harvested porcine eye. For each evaluation, the duration and the successful completion of the task was assessed. RESULTS: Robot-assisted vitreoretinal operations were successfully performed in nine rabbit eyes and 25 porcine eyes without any iatrogenic complication such as retinal tear or retinal detachment. In the task of using an endolaser, three rows of burns around the induced retinal hole were performed in nine rabbit eyes with half size intervals of laser spots. Nine procine eyes underwent PPV followed by successful posterior vitreous detachment (PVD) induction assisted with triamcinolone acetonide (TA). Nine porcine eyes completed removal of a fine stainless steel wire, which was inserted into prepared retinal tissue. Finally, retinal vascular cannulation with a piece of stainless steel wire (6mm length, 45 µm pipe diameter and one end cut to ∼30° slope) was successfully achieved in seven porcine eyes. The average duration of each procedure was 10.91±1.22 min, 11.68±2.11min, 5.90±0.46 min and 13.5±6.2 min, respectively. CONCLUSIONS: Maneuverability, accuracy and stability of robot-assisted vitreoretinal microsurgery using the RVRMS were demonstrated in this study. Wider application research of robotic surgery and improvement of a robotic system should be continued.

Non-contact wide-field viewing system-assisted scleral buckling surgery for retinal detachment in silicone oil-filled eyes.

AIM: To evaluate scleral buckling (SB) surgery using a non-contact wide-field viewing system and 23-gauge intraocular illumination for the treatment of rhegmatogenous retinal detachment in silicone oil (SO)-filled eyes. METHODS: Totally 9 patients (9 eyes) with retinal detachment in SO-filled eyes were retrospectively analyzed. All patients underwent non-contact wide-field viewing system-assisted buckling surgery with 23-gauge intraocular illumination. SO was removed at an appropriate time based on recovery. The patients were followed up for at least 3mo after SO removal. Retinal reattachment, complications, visual acuity and intraocular pressure (IOP) before and after surgery were observed. RESULTS: Patients were followed up for a mean of 8.22mo (3-22mo) after SO removal. All patients had retinal reattachment. At the final follow-up, visual acuity showed improvement for 8 patients, and no change for 1 patient. The IOP was high in 3 patients before surgery, but it stabilized after treatment; it was not affected in the other patients. None of the patients had infections, hemorrhage, anterior ischemia, or any other complication. CONCLUSION: This new non-contact wide-field viewing system-assisted SB surgery with 23-gauge intraocular illumination is effective and safe for retinal detachment in SO-filled eyes.

Characteristics of macular microvasculature before and after idiopathic macular hole surgery.

AIM: To evaluate the macular microvasculature before and after surgery for idiopathic macular hole (MH) and the association of preoperative vascular parameters with postoperative recovery of visual acuity and configuration. METHODS: Twenty eyes from 20 patients with idiopathic MH were enrolled. Optical coherence tomography angiography (OCTA) images were obtained before, 2wk, 1, and 3mo after vitrectomy with internal limiting membrane peeling. Preoperative foveal avascular zone (FAZ) area and perimeter and regional vessel density (VD) in both layers were compared according to the 3-month best-corrected visual acuity (BCVA). RESULTS: The BCVA improved from 0.98±0.59 (logMAR, Snellen 20/200) preoperatively to 0.30±0.25 (Snellen 20/40) at 3mo postoperatively. The preoperative deep VD was smaller and the FAZ perimeter was larger in the 3-month BCVA<20/32 group (all P<0.05). A significant reduction was observed in FAZ parameters and all VDs 2wk postoperatively. Except for deep perifoveal VD, all VDs recovered only to their preoperative values. The postoperative FAZ parameters were lower during follow-up. Decreases in preoperative deep VDs were correlated with worse postoperative BCVA (Pearson's r=-0.667 and -0.619, respectively). A larger FAZ perimeter (Spearman's r=-0.524) and a lower deep perifoveal VD preoperatively (Pearson's r=0.486) were associated with lower healing stage. CONCLUSION: The status of the deep vasculature may be an indicator of visual acuity in patients with a closed MH. Except for the deep perifoveal region, VD recovers only to preoperative levels.

Combining robot-assisted surgical system and 3D visualization system for teaching minimally invasive vitreoretinal surgery.

AIM: To investigate the feasibility of teaching minimally invasive vitreoretinal surgery with a robot-assisted surgical system and a three-dimensional (3D) visualization system. METHODS: Enucleated porcine eyes were established as an animal model for removing foreign bodies. Forty medical students were recruited to remove foreign bodies to compare the traditional microscope and the 3D system. One junior resident performed the surgical task with manual and robot-assisted operations on 20 porcine eyes for each group. One senior surgeon evaluated the retinal invasion by a graded injury degree. The learning curve for minimally invasive vitreoretinal surgery was described. RESULTS: Compared with the robot-assisted group, the injury degree was higher in the manual group. For the first ten surgeries, the manual and robot-assisted groups had injuries of 2.60±1.35 (4 to 0) and 1.80±1.62 (4 to 0), respectively. For the last ten surgeries, the injury degrees were 1.90±1.20 (3 to 0) and 0.80±0.42 (1 to 0). Considering the manual and robot-assisted groups together, 95%, 75% and 60% of the students considered surgical manipulation with the 3D visualization system to be more comfortable, easier and clearer, respectively. CONCLUSION: The robot-assisted surgical system and 3D visualization system may have value in teaching minimally invasive vitreoretinal surgery.

Comparison of persistent submacular fluid in different preoperative macular status after vitrectomy for rhegmatogenous retinal detachment.

AIM: To compare the incidence of persistent submacular fluid (SMF) and visual outcome after pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment (RRD) in different preoperative macular status according to optical coherence tomography (OCT). METHODS: A non-randomized, retrospective review was performed for patients who underwent successful PPV for RRD. OCT exams were taken preoperatively and 1mo after surgery, until SMF disappeared. According to the preoperative macular status on OCT, patients were divided into two groups: macula-off RRD (Group A) and macula-on RRD (Group B). In Group A, there were two subgroups: macula partly detached (Group A1) and macula totally detached (Group A2). The main outcome measures were the presence of SMF on OCT 1mo after surgery, and the preoperative and postoperative best corrected visual acuities (BCVA), among the different groups and depending on the presence or absence of persistent SMF. RESULTS: A total of 139 eyes of 139 patients were included in the study. Persistent SMF at 1mo after surgery was 15.8% (22/139), all occurring in Group A (22/101); Group B had no SMF at 1mo after surgery (0/38, P=0.002). The incidence of persistent SMF at 1mo after surgery in Group A1 was 50% (14/28), and in Group A2 was 11.0% (8/73, P<0.001). Significant differences were shown between the presence and absence of persistent SMF on foveola-off RRD, the preoperative BCVA, the 1mo postoperative BCVA, and the degree of the BCVA improvement from 1mo postoperatively to the final follow-up (P<0.05). However, there were no significant differences in the final BCVA (P>0.05). CONCLUSION: Persistent SMF after PPV for retinal detachment is associated with preoperative macular status. Macula-uninvolving RRD shows no persistent SMF after PPV. Macular partly detached RRD has a higher incidence of SMF than macula totally detached RRD after PPV. The persistence of SMF may be responsible for the delayed visual recovery, whereas there were no significant differences in the final visual acuity.

Effect of intravitreal conbercept treatment before vitrectomy in proliferative diabetic retinopathy.

AIM: To evaluate the safety and efficacy of intravitreal conbercept (IVC) injections as pretreatment for pars plana vitrectomy (PPV) in severe proliferative diabetic retinopathy (PDR). METHODS: This was a retrospective chart review of all patients who underwent PPV for PDR from January 2014 to October 2016. Patients who underwent IVC injection before PPV were assigned to the IVC group; the others were assigned to the control group. The IVC was performed 3-7d before surgery in the IVC group. All the eyes in the two groups were operated by the same doctor to complete the vitrectomy. Intraoperative complications and the changes in best-corrected visual acuity (BCVA) before and after surgery were compared between the two groups. RESULTS: A total of 68 eyes of 63 patients (22 eyes in the IVC group and 46 eyes in the control group) were examined. The risk of intraoperative bleeding was lower in the IVC group (2/22) than in the control group (25/46, P=0.000). Furthermore, the use of endodiathermy was significantly lower in the IVC group (1/22) than in the control group (12/46, P=0.047). The surgical time in the IVC group (112.64±34.52min) was significantly shorter than in the control group (132.85±40.04min, P<0.05). Compared to the BCVA before surgery, the mean BCVA was significantly improved after surgery for both groups (P<0.05). CONCLUSION: PPV is an effective treatment and can improve vision in patients with PDR. Preoperative intravitreal injection of conbercept could reduce the chances of intraoperative bleeding and the use of endodiathermy and shorten the operative time, which are beneficial in the management of PDR.

Feasibility study on robot-assisted retinal vascular bypass surgery in an ex vivo porcine model.

PURPOSE: To describe a new robot-assisted surgical system for retinal vascular bypass surgery (RVBS) and to compare the success rate with freehand RVBS. METHODS: A robot-assisted system for retinal microsurgery was constructed to include two independent robotic arms. A 23-gauge light probe and an intraocular forceps were affixed to the arm end effectors to perform the intraocular manipulation. Harvested porcine eyes were introduced to be established animal models of closed-sky eyeballs after that pars plana vitrectomy using temporary keratoprosthesis was performed by a skilful surgeon. Retinal vascular bypass surgery (RVBS) was performed by an inexperienced ophthalmologist to test the ease of use. A stainless steel wire (45-µm pipe diameter) was used as an artificial vessel. Before RVBS, the wires were prepositioned at the retinal surface of the eyes. The Control group (n = 20) underwent freehand RVBS, and the Experimental group (n = 20) underwent robot-assisted RVBS. To create the simulated bypass, the distal end of the wire was inserted into the selected vessel and advanced ~4 mm away from the optic disc. If successful, then the proximal wire end was inserted and advanced ~2 mm towards the optic disc. The difference in the success rate for the freehand and robot-assisted procedures was analysed by the chi-square test. RESULTS: The success rate for the freehand RVBS was 5% (1/20 eyes). In contrast, the robot-assisted success rate was 35% (7/20) of eyes (p < 0.05). CONCLUSION: This study demonstrated the feasibility of robot-assisted RVBS in ex vivo porcine eyes. The robotic system increased the accuracy and stability of manipulation by eliminating freehand tremor, leading to a higher surgical success rate.