Postoperative vision loss due to bilateral vitreous hemorrhage after robot-assisted laparoscopic hysterectomy: A case report.

Purpose: To report a case of bilateral vitreous hemorrhage (VH) resulting in postoperative vision loss (POVL) after robot-assisted laparoscopic hysterectomy in a 71-year-old female patient. Observations: At initial presentation, best-corrected visual acuity was hand motion at 20 cm in the right eye and 20/666 in the left eye. VH in both eyes and preretinal hemorrhage in the left eye was observed. As the hemorrhage gradually resolved, a full-thickness macular hole was discovered in the right eye, for which the patient did not agree with a surgical treatment. Conclusions and importance: This report describes a rare incidence of bilateral VH as a cause of POVL after non-ophthalmic surgery, which may be related to Trendelenburg positioning, CO2 pneumoperitoneum, and a long surgical duration. Given that POVL can cause severe visual impairment, consultation with ophthalmologists is crucial.

Encircling continuous suture technique for the management of extensive traumatic cyclodialysis: A case report.

PURPOSE: To report a surgical technique of cyclopexy, wherein two laps of encircling continuous sutures are placed around the limbus to treat refractory extensive cyclodialysis. METHODS: Color fundus photography, swept-source optical coherence tomography (OCT) for the anterior segment, and spectral-domain OCT for the macula. RESULTS: Previous attempts, including indirect cyclopexy and direct external cyclopexy with gas injection, failed to successfully resolve the severe cyclodialysis and associated hypotonic maculopathy. In the third surgery, two laps of encircling continuous sutures were placed around the limbus at the distances of 2-3 mm and 3-4 mm, along with phacoemulsification, intraocular lens implantation, and capsular tension ring placement. Following the surgery, hypotony and hypotonic maculopathy were effectively resolved, resulting in a significant improvement in visual acuity, that has been maintained over a year. CONCLUSION: The described surgical technique of encircling continuous sutures may be a viable option for the treatment of severe cyclodialysis.

RECENT TRENDS IN THE CUMULATIVE INCIDENCE AND INTERVENTION PATTERNS OF RETINOPATHY OF PREMATURITY IN JAPAN: A Multicenter Analysis, 2011-2020.

PURPOSE: To investigate recent trends in the cumulative incidence and treatment patterns of retinopathy of prematurity (ROP) in Japan. METHODS: A retrospective multicenter cohort was conducted from 2011 to 2020 using the Diagnosis Procedure Combination inpatient database. Preterm newborns with birth weight <2,500 g were categorized by birth weight. The cumulative incidence of ROP, treatment patterns, and association between treatment and birth weight were investigated. RESULTS: A total of 82,683 preterm infants were identified, of whom 9,335 (11.3%) were diagnosed with ROP. The cumulative incidence of ROP increased by 15% in those with birth weight <500 g over the study period. Among the ROP infants, 20.2% received treatment, including laser photocoagulation (94.8%), intravitreal injection (3.8%), or both (1.8%). The proportion receiving laser photocoagulation decreased followed by an increase in intravitreal injection. This shift in intervention pattern was most conspicuous for those with birth weight 750 to 1,249 g. The risk ratio of receiving laser and intravitreal injection for those weighing <500 g was 24.7 (95% confidence interval, 10.5-58.2) and 28.4 (5.8-138.1), respectively, as compared with infants weighing >1,500 g. CONCLUSION: The cumulative incidence of ROP increased in infants with birth weight <500 g. A shift from laser photocoagulation to intravitreal injection was observed in the more recent years.

Navigated direct photocoagulation with a 30-ms short-pulse laser for treating microaneurysms in diabetic macular edema exhibits a high closure rate.

This study carried out direct photocoagulation for treating microaneurysms (MAs) in diabetic macular edema (DME) using a navigation laser system with a 30-ms pulse duration. The MA closure rate after 3 months was investigated using pre and postoperative fluorescein angiography images. MAs primarily inside the edematous area based on optical coherence tomography (OCT) maps were selected for treatment, and leaking MAs (n = 1151) were analyzed in 11 eyes (eight patients). The total MA closure rate was 90.1% (1034/1151), and the mean MA closure rate in each eye was 86.5 ± 8.4%. Mean central retinal thickness (CRT) decreased from 471.9 ± 73.0 µm to 420.0 ± 87.5 µm (P = 0.049), and there was a correlation between the MA closure rate and the CRT reduction rate (r = 0.63, P = 0.037). There was no difference in the MA closure rate depending on the degree of edema thickness based on a false-color topographic OCT map image. Direct photocoagulation for DME with a short pulse using the navigated photocoagulator resulted in a high MA closure rate in just 3 months and a corresponding improvement in retinal thickness. These findings encourage the use of a new therapeutic approach for DME.

Microperimetric analysis of diabetic macular edema after navigated direct photocoagulation with short-pulse laser for microaneurysms.

BACKGROUND: Focal laser photocoagulation is an important treatment option for diabetic macular edema (DME). This study aimed to examine the retinal sensitivity (RS) and morphological changes at the coagulated site after direct photocoagulation of microaneurysms (MAs) in patients with DME using a navigated laser photocoagulator with a short-pulse duration of 30 ms. METHODS: Images of early-phase fluorescein angiography were merged with images from the optical coherence tomography (OCT) map with 9 Early Treatment Diabetic Retinopathy Study grid circles, and MAs inside the edema area were selected for direct photocoagulation. The best-corrected visual acuity (BCVA), parameters of the OCT map including central retinal thickness and retinal thickness in edema range, central RS, and RS in the edema area were assessed at 1 and 3 months after the laser treatment. The RS points that overlapped with the laser spots were identified by merging the Navilas' digital treatment reports and the microperimetry images. RESULTS: Seventeen eyes from 14 patients were studied. The mean retinal thickness in the edema range decreased at 3 months compared with pretreatment (P = 0.042), but the BCVA, central retinal thickness, central RS, and RS in the edema area remained unchanged. Overall, 32 of 400 sensitivity points overlapped with the laser-coagulated spots. The mean RS at these spots were 22.4 ± 5.3 dB at 1 month and 22.5 ± 4.8 dB at 3 months, with no significant change from the baseline of 22.7 ± 3.5 dB. CONCLUSIONS: Retinal thickness improved in the coagulated edema area without a decrease in RS after direct photocoagulation of MAs with a short 30-ms pulse using Navilas. This promising therapeutic strategy for DME is effective and minimally invasive.

Optical coherence tomography findings after surgery for sub-inner limiting membrane hemorrhage due to ruptured retinal arterial macroaneurysm.

Ruptured retinal arterial macroaneurysm (RAM) can cause sub-inner limiting membrane (ILM) hemorrhage, leading to acute vision loss in the elderly. Vitrectomy has been established as an effective treatment to remove hemorrhage and facilitate visual recovery. Although optical coherence tomography (OCT) is useful for the diagnosis of sub-ILM hemorrhage before surgery, little is known about the postoperative OCT findings. Here, we retrospectively investigated the records of nine eyes of nine patients who underwent surgery for sub-ILM hemorrhage due to RAM rupture. On postoperative OCT, hyperreflectivity throughout the full thickness of the central fovea was observed in eight eyes (88.9%), and disruption of the ellipsoid/interdigitation zone (EZ/IZ) was observed in seven out of eight eyes (87.5%). The widths of the hyperreflectivity and EZ disruption gradually decreased. Visual recovery was least favorable in two eyes, in which the EZ line continuation did not recover until the final follow-up. The OCT findings corresponded to the hemorrhagic staining identified on fundus photographs in at least four eyes; as per the fundus photographs the findings persisted even after the hemorrhage was absorbed. In contrast, the OCT findings resembled the appearance before the development of a full-thickness macular hole, suggesting fragility caused by the RAM rupture.

A force measurement platform for a vitreoretinal surgical simulator using an artificial eye module integrated with a quartz crystal resonator.

To provide quantitative feedback on surgical progress to ophthalmologists practicing inner limiting membrane (ILM) peeling, we developed an artificial eye module comprising a quartz crystal resonator (QCR) force sensor and a strain body that serves as a uniform force transmitter beneath a retinal model. Although a sufficiently large initial force must be loaded onto the QCR force sensor assembly to achieve stable contact with the strain body, the highly sensitive and wide dynamic-range property of this sensor enables the eye module to detect the slight forceps contact force. A parallel-plate strain body is used to achieve a uniform force sensitivity over the 4-mm-diameter ILM peeling region. Combining these two components allowed for a measurable force range of 0.22 mN to 29.6 N with a sensitivity error within -11.3 to 4.2% over the ILM peeling area. Using this eye module, we measured the applied force during a simulation involving artificial ILM peeling by an untrained individual and compensated for the long-term drift of the obtained force data using a newly developed algorithm. The compensated force data clearly captured the characteristics of several types of motion sequences observed from video recordings of the eye bottom using an ophthalmological microscope. As a result, we succeeded in extracting feature values that can be potentially related to trainee skill level, such as the mean and standard deviation of the pushing and peeling forces, corresponding, in the case of an untrained operator, to 122.6 ± 95.2 and 20.4 ± 13.2 mN, respectively.

Bionic eye system mimicking microfluidic structure and intraocular pressure for glaucoma surgery training.

Among increasing eye diseases, glaucoma may hurt the optic nerves and lead to vision loss, the treatment of which is to reduce intraocular pressure (IOP). In this research, we introduce a new concept of the surgery simulator for Minimally Invasive Glaucoma Surgery (MIGS). The concept is comprised of an anterior eye model and a fluidic circulatory system. The model made of flexible material includes a channel like the Schlemm's canal (SC) and a membrane like the trabecular meshwork (TM) covering the SC. The system can monitor IOP in the model by a pressure sensor. In one of the MIGS procedures, the TM is cleaved to reduce the IOP. Using the simulator, ophthalmologists can practice the procedure and measure the IOP. First, considering the characteristics of human eyes, we defined requirements and target performances for the simulator. Next, we designed and manufactured the prototype. Using the prototype, we measured the IOP change before and after cleaving the TM. Finally, we demonstrated the availability by comparing experimental results and target performances. This simulator is also expected to be used for evaluations and developments of new MIGS instruments and ophthalmic surgery robots in addition to the surgical training of ophthalmologists.

Differential gene expression analysis using RNA sequencing: retinal pigment epithelial cells after exposure to continuous-wave and subthreshold micropulse laser.

PURPOSE: Subthreshold micropulse laser (SMPL) is more clinically efficient for the treatment of diabetic macular edema (DME) than the conventional continuous-wave (CW) laser. We aimed to characterize transcriptome changes after the application of these lasers and to compare the transcripts. METHODS: Human pluripotent stem cell-derived retinal pigment epithelial cells were exposed to laser irradiation. Differentially expressed genes (DEGs), distribution of heat shock protein (Hsp) family, gene expression profile, and gene ontology (GO) enrichment analysis based on RNA sequencing data were investigated at 3 h and 24 h after irradiation. RESULTS: CW laser induced more DEGs than SMPL (1771 vs. 520 genes). The expression of the Hsp family was confirmed in both groups: however, the induction patterns was different for different genes. GO enrichment analysis revealed that CW laser upregulated the expression of DEGs involved in vasculature development (GO: 0001944), related to apoptosis and repair after cell injury whereas SMPL upregulated the expression of DEGs involved in photoreceptor cell maintenance (GO: 0045494), photoreceptor cell development (GO: 0042461), and sensory perception of light stimuli (GO: 0050953). CONCLUSIONS: The results provide insights into the genetic responses and may contribute to the understanding of the molecular mechanisms of laser-induced thermal effects.

More Accurate Diagnosis of Vitreoretinal Lymphoma Using a Combination of Diagnostic Test Results: A Prospective Observational Study.

PURPOSE: To establish diagnostic criteria for vitreoretinal lymphoma (VRL) using cytology and laboratory tests from vitreous samples: interleukin (IL)-10/IL-6 ratio, immunoglobulin (Ig) H gene rearrangement, and clonal B-cells on flow cytometry. METHODS: Fifty-six patients with and 39 without VRL were included. We assessed the sensitivity and specificity of each test and those of diagnostic criteria based on combinations of these tests. RESULTS: The sensitivity values for malignant cytology, IL-10/IL-6 > 1, IgH gene rearrangement, and flow cytometry were 0.554, 0.821, 0.732, and 0.625 with specificity of 1.000, 1.000, 0.846, and 0.974, respectively. When the diagnostic criteria were set at malignant cytology or at two or more of of four tests (atypical cells, IL-10/IL-6 > 1, IgH gene rearrangement, and flow cytometry), the sensitivity and specificity values for accurate diagnosis were 0.929 and 1.00, respectively. CONCLUSION: Malignant cytology or positive results for two or more of four tests may be adequate for VRL diagnosis.

Changes in entropy on polarized-sensitive optical coherence tomography images after therapeutic subthreshold micropulse laser for diabetic macular edema: A pilot study.

PURPOSE: To investigate the dynamics of the healing process after therapeutic subthreshold micropulse laser (SMPL) for diabetic macular edema (DME) using polarization-sensitive optical coherence tomography (PS-OCT). METHODS: Patients with treatment-native or previously-treated DME were prospectively imaged using PS-OCT at baseline, 1, 2, 3, and 6 months. The following outcomes were evaluated: changes in the entropy value per unit area (pixel2) in the retinal pigment epithelium (RPE) on the B-scan image; changes in the entropy value in each stratified layer (retina, RPE, choroid) based on the ETDRS grid circle overlaid with en face entropy mapping, not only the whole ETDRS grid area but also a sector irradiated by the SMPL; and the relationship between edema reduction and entropy changes. RESULTS: A total of 11 eyes of 11 consecutive DME patients were enrolled. No visible signs of SMPL treatment were detected on PS-OCT images. The entropy value per unit area (pixel2) in the RPE tended to decrease at 3 and 6 months from baseline (35.8 ± 17.0 vs 26.1 ± 9.8, P = 0.14; vs 28.2 ± 18.3, P = 0.14). Based on the en face entropy mapping, the overall entropy value did not change in each layer in the whole ETDRS grid; however, decrease of entropy in the RPE was observed at 2, 3, and 6 months post-treatment within the SMPL-irradiated sectors (P < 0.01, each). There was a positive correlation between the change rate of retinal thickness and that of entropy in the RPE within the SMPL-irradiated sector at 6 months (r2 = 0.19, P = 0.039). CONCLUSION: Entropy measured using PS-OCT may be a new parameter that facilitates objective monitoring of SMPL-induced functional changes in the RPE that could not previously be assessed directly. This may contribute to a more promising therapeutic evaluation of DME. CLINICAL TRIAL: This clinical study was registered in UMIN-CTR (ID: UMIN000042420).

Surgical Treatment for a Full-Thickness Macular Hole That Developed on a Large Drusenoid Pigment Epithelial Detachment.

Full-thickness macular hole (FTMH) and age-related macular degeneration (AMD) can affect the same eyes in the older population. Previously reported phenotypes of AMD concurrent with FTMH include early/intermediate AMD and serous pigment epithelial detachment (PED). A 68-year-old woman presented to our clinic with decreased vision due to a cataract and a large drusenoid PED in both eyes. After ruling out choroidal neovascularization, she underwent cataract surgery. Three days after the cataract surgery, an FTMH was found in the left eye. Although the FTMH was not closed after the initial pars plana vitrectomy (PPV) with the inner limiting membrane (ILM) peeling and air tamponade, it was closed after reoperation with additional ILM peeling, retinal massage, and SF6 gas tamponade. Best-corrected visual acuity (BCVA) was improved from 20/60 before the first PPV to 20/40 at six months after the reoperation. Some large soft drusen in the macula were fused after surgeries in the operated eye, but not in the fellow eye. An FTMH concurrent with a large drusenoid PED is rare. It can be closed surgically, and postoperative visual function can improve.

Fovea-Sparing as Opposed to Total Peeling of Internal Limiting Membrane for Myopic Foveoschisis: A Systematic Review and Meta-analysis.

TOPIC: The effectiveness of fovea-sparing (FS) peeling of internal limiting membrane (ILM) to treat myopic foveoschisis (MF) has not been understood fully. The present meta-analysis aimed to compare postoperative visual and anatomic outcomes between FS peeling and total peeling (TP) of ILM in pars plana vitrectomy for the treatment of MF. CLINICAL RELEVANCE: Postoperative macular hole (MH) development is not uncommon and is a serious complication after surgery for MF, with poor visual prognosis. Fovea-sparing peeling of ILM is expected to reduce the risk of postoperative MH; however, no statistically significant evidence exists to prove this hypothesis. In addition, its effect on postoperative visual acuity has not been clear. METHODS: MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE were reviewed systematically, and studies that compared FS with total ILM peeling in MF surgery were retrieved. The protocol was registered in International Prospective Register of Systematic Reviews (identifier, CRD42020201675). Primary outcome measures were the postoperative best-corrected visual acuity (BCVA) and frequency of postoperative MH development. Certainty of evidence was evaluated by the Grading of Recommendations Assessment, Development and Evaluation system. RESULTS: Eight studies with 300 eyes from 289 patients were included. All studies were nonrandomized and observational. The postoperative BCVA was significantly better in eyes treated with FS (mean difference [MD], -0.15 logarithm of the minimum angle of resolution [logMAR]; 95% confidence interval [CI], -0.24 to -0.05 logMAR; P = 0.002). The risk of postoperative MH was significantly lower in the FS group (odds ratio, 0.19; 95% CI, 0.06-0.56; P = 0.003). No significant difference was found in postoperative central foveal thickness (MD, 12.59 µm; 95% CI, -2.8 to 28.0 µm; P = 0.11). The certainty of evidence regarding lower frequency of postoperative MH after FS peeling was considered moderate, whereas the certainty regarding better postoperative BCVA after FS peeling was judged to be low. DISCUSSION: Fovea-sparing peeling may contribute to better visual acuity outcome and lower risk of postoperative MH development in eyes with MF.

Continued smoking and posterior vitreous adhesion in the elderly evaluated on swept-source optical coherence tomography.

In this cross-sectional study including 1150 eyes of 681 volunteers ≧ 65 years old without retinal pathology, factors affecting the progression of posterior vitreous detachment (PVD) were investigated. PVD stages were diagnosed based on swept-source optical coherence tomography (SS-OCT). Linear mixed effect model was used to determine whether age, gender, diabetes mellitus (DM), hypertension (HT), dyslipidemia (DL), and smoking status were associated with various stages of PVD. As a result, the multivariable analysis disclosed that the associations between older age and higher PVD stages (estimate [95% CI], 0.031 [0.020 to 0.042]; P < 0.0001), and current smokers and lower PVD stages (estimate [95% CI], - 0.24 [- 0.43 to - 0.056]; P = 0.011) were statistically significant. In contrast, female gender was not an independent factor affecting PVD stages in the elderly. Our analysis indicated that higher PVD stages observed in female eyes may be due to confounding effect, in which current smokers were predominantly males (i.e., 12.6% among males vs. 3.9% among females, P < 0.0001). In conclusion, our findings suggest that continuous smoking is associated with an adherent vitreoretinal interface in the elderly.

Posterior vitreous detachment and macular microvasculature in the elderly.

PURPOSE: To investigate the association between different stages of posterior vitreous detachment (PVD) and macular microvasculature in the elderly. METHODS: Swept-source optical coherence tomography (OCT), OCT angiography, and color fundus images of 490 eyes without retinal pathologies of 322 participants aged ≥65 years were evaluated. PVD was classified using enhanced vitreous visualization mode as no apparent PVD (stage 0/1), vitreous adhesions at the fovea and optic disc (stage 2), adhesion at the optic disc (stage 3), or complete PVD (stage 4). Microvascular parameters, including foveal avascular zone (FAZ) and vessel density (VD), were analyzed for their associations with complete PVD. Additionally, the association between PVD and central retinal thickness (CRT) was also addressed. RESULTS: Overall, 80, 31, 31, and 349 eyes were categorized into stages 0/1, 2, 3, and 4, respectively. Using multivariate mixed-effects model, the mean superficial FAZ area was smaller in stage 4 compared with stages 0-3 (0.29 vs. 0.32 mm2; P = 0.014), and the mean superficial VD was lower in stage 4 compared with stages 0-3 (34.96% vs. 35.24%; P = 0.0089). However, PVD was not significantly associated with deep macular microvascular parameters or CRT. CONCLUSIONS: Complete PVD was associated with smaller FAZ area and lower VD in superficial macular microvasculature, while it was not associated with central retinal thickness.

Correlation between anterior chamber flare changes and diabetic macular edema after intravitreal injection of ranibizumab and aflibercept.

PURPOSE: To evaluate aqueous flare change patterns following anti-vascular endothelial growth factor therapy for diabetic macular edema (DME) and investigate the relationship between changes in flare values and central macular thickness (CMT). STUDY DESIGN: Retrospective, interventional case series METHODS: A total of 84 eyes of 62 patients with DME received either intravitreal ranibizumab (IVR; n = 62) or aflibercept (IVA; n = 22). A laser flare photometer (Kowa FM500, Kowa Company, Ltd) was used to measure flare values, and CMT was assessed using optical coherence tomography. Flare values and CMT were measured prior to injection (baseline) and at, 1, 7 and 14 days after injection. RESULTS: Flare values in the IVR group decreased significantly at day 14 (P = 0.001), whereas the IVA group showed a significant increase in flare values at day 1 (P < 0.001). In the IVA group, the baseline flare values were significantly higher in the CMT reduction group than in the non-CMT reduction group (P = 0.035). There was no correlation between changes in flare values and CMT either in the IVA or IVR group. CONCLUSIONS: Flare value changes in patients treated with IVR decreased at day 14 post-injection. This may indicate when the most anti-inflammatory effect was obtained. There was no correlation between changes in flare values and CMT either in the IVA or IVR group; nevertheless, our research suggests that the baseline flare value is a predictive factor for the efficacy of IVA in DME.

Prospective evaluation of visual function in patients with ocular diseases after robot-assisted laparoscopic prostatectomy.

OBJECTIVES: To investigate intraocular pressure and visual function in patients with ocular diseases undergoing robot-assisted laparoscopic prostatectomy. METHODS: We carried out a prospective clinical study of patients undergoing robot-assisted laparoscopic prostatectomy for localized prostate cancer at The University of Tokyo Hospital from December 2015 to March 2017. An ophthalmologist measured intraocular pressure, and carried out visual field testing at 0-2 months before and 7 days after robot-assisted laparoscopic prostatectomy. During the surgery, an anesthesiologist measured intraocular pressure at specified time points. RESULTS: A total of 110 patients were enrolled and 98 eligible patients were analyzed; 37 were diagnosed with ocular diseases before robotic-assisted laparoscopic prostatectomy (17 with glaucoma, 20 with other ocular diseases). Intraocular pressure significantly increased during robot-assisted laparoscopic prostatectomy. Transient postoperative visual field defect was detected in 24 eyes of 17 patients, including six patients with ocular diseases at 7 days after surgery. At 3 months after surgery, one of 34 glaucomatous eyes and one of 40 eyes with non-glaucomatous ocular diseases continued to show visual field defect, although visual field defect in the remaining patients recovered to preoperative conditions within 3 months. CONCLUSIONS: Our findings suggest that robot-assisted laparoscopic prostatectomy can be safely carried out in patients with ocular diseases, even those with glaucoma, after precautionary consultation with an ophthalmologist.

Ursodeoxycholic Acid Attenuates the Retinal Vascular Abnormalities in Anti-PDGFR-ß Antibody-Induced Pericyte Depletion Mouse Models.

As a clinical manifestations of diabetic retinopathy (DR), pericytes (PCs) loss from the capillary walls is thought to be an initial pathological change responsible for the breakdown of the blood-retinal barrier (BRB). This study was performed to investigate the effects of ursodeoxycholic acid (UDCA) in PC depletion mice by injection of an antibody against platelet-derived growth factor reception-ß (PDGFR-ß clone APB5). To assess the integrity of the retinal vessels, their density, diameters, vessel branching points, and number of acellular capillaries were evaluated. While all types of retinal vessels became enlarged in APB5-induced mice, treatment with UDCA rescued the vasculature; the vessel density, diameter of the veins and capillaries, and vessel branching points were significantly lower in mice treated with UDCA. Although APB5-induced mice displayed progressive exacerbation of retinal edema, whole retinal thickness upon treatment with UDCA was significantly decreased. Additionally, UDCA reduced the expression of F4/80+ macrophages in the APB5-induced retina according to immunofluorescent labeling. UDCA also reduced the increased expression of angiogenic factors and inflammatory mediators (vascular endothelial growth factor, intercellular adhesion molecule-1, and monocyte chemotactic protein-1). These findings suggest that UDCA can be used to prevent the progression of and treat DR.

Development of a Spherical Model with a 3D Microchannel: An Application to Glaucoma Surgery.

Three-dimensional (3D) microfluidic channels, which simulate human tissues such as blood vessels, are useful in surgical simulator models for evaluating surgical devices and training novice surgeons. However, animal models and current artificial models do not sufficiently mimic the anatomical and mechanical properties of human tissues. Therefore, we established a novel fabrication method to fabricate an eye model for use as a surgical simulator. For the glaucoma surgery task, the eye model consists of a sclera with a clear cornea; a 3D microchannel with a width of 200-500 µm, representing the Schlemm's canal (SC); and a thin membrane with a thickness of 40-132 µm, representing the trabecular meshwork (TM). The sclera model with a clear cornea and SC was fabricated by 3D molding. Blow molding was used to fabricate the TM to cover the inner surface of the sclera part. Soft materials with controllable mechanical behaviors were used to fabricate the sclera and TM parts to mimic the mechanical properties of human tissues. Additionally, to simulate the surgery with constraints similar to those in a real operation, the eye model was installed on a skull platform. Therefore, in this paper, we propose an integration method for fabricating an eye model that has a 3D microchannel representing the SC and a membrane representing the TM, to develop a glaucoma model for training novice surgeons.

Autonomous Positioning of Eye Surgical Robot Using the Tool Shadow and Kalman Filtering.

Vitreoretinal surgery is one of the most difficult surgical operations, even for experienced surgeons. Thus, a master-slave eye surgical robot has been developed to assist the surgeon in safely performing vitreoretinal surgeries; however, in the master-slave control, the robotic positioning accuracy depends on the surgeon's coordination skills. This paper proposes a new method of autonomous robotic positioning using the shadow of the surgical instrument. First, the microscope image is segmented into three regions-namely, a micropipette, its shadow, and the eye ground-using a Gaussian mixture model (GMM). The tips of the micropipette and its shadow are then extracted from the contour lines of the segmented regions. The micropipette is then autonomously moved down to the simulated eye ground until the distance between the tips of micropipette and its shadow in the microscopic image reaches a predefined threshold. To handle possible occlusions, the tip of the shadow is estimated using a Kalman filter. Experiments to evaluate the robotic positioning accuracy in the vertical direction were performed. The results show that the autonomous positioning using the Kalman filter enhanced the accuracy of robotic positioning.