A Novel Tissue Identification Framework in Cataract Surgery Using an Integrated Bioimpedance-Based Probe and Machine Learning Algorithms.

OBJECTIVE: The objective of this work was to develop and experimentally validate a bioimpedance-based framework to identify tissues in contact with the surgical instrument during cataract surgery. METHODS: This work introduces an integrated hardware and software solution based on the unique bioimpedance of different intraocular tissues. The developed hardware can be readily integrated with commonly used surgical instruments. The proposed software framework, which encompasses data acquisition and a machine-learning classifier, is fast enough to be deployed in real-time surgical interventions. The experimental protocol included bioimpedance data collected from 31 ex vivo pig eyes targeting four intraocular tissues: Iris, Cornea, Lens, and Vitreous. RESULTS: A classifier based on a support vector machine exhibited an overall accuracy of 91% across all trials. The algorithm provided substantial performance in detecting the intraocular tissues with 100% reliability and 95% sensitivity for the lens, along with 88% reliability and 94% sensitivity for the vitreous. CONCLUSION: The developed impedance-based framework demonstrated successful intraocular tissue identification. SIGNIFICANCE: Clinical implications include the ability to ensure safe operations by detecting posterior capsule rapture with 94% probability and improving surgical efficacy through lens detection with 100% reliability.

[Optical coherence tomography biomarkers in epimacular membranes and vitreomacular traction syndrome]. / Optische Kohärenztomographie-Biomarker bei epimakulären Membranen und vitreomakulärem Traktionssyndrom.

Using high-resolution imaging, such as optical coherence tomography (OCT), the different layers of the retina as well as the vitreoretinal interface and its alterations can be very clearly differentiated. This includes the morphological characteristics of tractive maculopathies, such as epiretinal gliosis and vitreomacular traction syndrome. Additionally, structural alterations of the various layers of the neurosensory retina as a result of traction due to these pathologies can be demarcated. The latter have been investigated in clinical trials and evaluated as OCT biomarkers with respect to their prognostic and predictive value. In this review we would like to present and discuss various OCT biomarkers in the context of epimacular membranes and vitreomacular traction syndrome.

Towards automatic detection of abnormal retinal capillaries in ultra-widefield-of-view retinal angiographic exams.

Retinal capillary abnormalities include small, leaky, severely tortuous blood vessels that are associated with a variety of retinal pathologies. We present a prototype image-processing system for detecting abnormal retinal capillary regions in ultra-widefield-of-view (UWFOV) fluorescein angiography exams of the human retina. The algorithm takes as input an UWFOV FA frame and returns the candidate regions identified. An SVM classifier is trained on regions traced by expert ophthalmologists. Tests with a variety of feature sets indicate that edge features and allied properties differentiate best between normal and abnormal retinal capillary regions. Experiments with an initial set of images from patients showing branch retinal vein occlusion (BRVO) indicate promising area under the ROC curve of 0.950 and a weighted Cohen's Kappa value of 0.822.

Robot-assisted intraocular surgery: development of the IRISS and feasibility studies in an animal model.

PURPOSE: The aim of this study is to develop a novel robotic surgical platform, the IRISS (Intraocular Robotic Interventional and Surgical System), capable of performing both anterior and posterior segment intraocular surgery, and assess its performance in terms of range of motion, speed of motion, accuracy, and overall capacities. PATIENTS AND METHODS: To test the feasibility of performing 'bimanual' intraocular surgical tasks using the IRISS, we defined four steps out of typical anterior (phacoemulsification) and posterior (pars plana vitrectomy (PPV)) segment surgery. Selected phacoemulsification steps included construction of a continuous curvilinear capsulorhexis and cortex removal in infusion-aspiration (I/A) mode. Vitrectomy steps consisted of performing a core PPV, followed by aspiration of the posterior hyaloid with the vitreous cutter to induce a posterior vitreous detachment (PVD) assisted with triamcinolone, and simulation of the microcannulation of a temporal retinal vein. For each evaluation, the duration and the successful completion of the task with or without complications or involuntary events was assessed. RESULTS: Intraocular procedures were successfully performed on 16 porcine eyes. Four eyes underwent creation of a round, curvilinear anterior capsulorhexis without radialization. Four eyes had I/A of lens cortical material completed without posterior capsular tear. Four eyes completed 23-gauge PPV followed by successful PVD induction without any complications. Finally, simulation of microcannulation of a temporal retinal vein was successfully achieved in four eyes without any retinal tears/perforations noted. CONCLUSION: Robotic-assisted intraocular surgery with the IRISS may be technically feasible in humans. Further studies are pending to improve this particular surgical platform.

Evaluation of the motion of surgical instruments during intraocular surgery.

PURPOSE: Robot assistance in ocular microsurgery could improve precision, dexterity, save time or prevent complications by task automation, and provide access to ocular surgery in undeserved countries by teleoperation. However, to design robotic devices, the range of motion of surgical instruments needs to be precisely quantified. METHODS: An electromagnetic tracking system was developed for intraocular surgery in order to quantify the movements of ophthalmic surgeons. Kinematics of surgical steps during phacoemulsification and pars plana vitrectomy procedures were determined by measuring the maximum translation and angular range of motion of intraocular surgical tools in the three planes. CONCLUSION: Important variations in amplitudes of rotation and translation were measured between both hands and between surgical tasks. These parameters may be used to develop a robotic intraocular surgical system or to improve training.

Improving vessel segmentation in ultra-wide field-of-view retinal fluorescein angiograms.

Vessel segmentation on ultra-wide field-of-view fluorescein angiogram sequences of the retina is a challenging problem. Vessel appearance undergoes severe changes, as different portions of the vascular structure become perfused in different frames. This paper presents a method for segmenting vessels in such sequences using steerable filters and automatic thresholding. We introduce a penalization stage on regions with high vessel response in the filtered image, improving the detection of peripheral vessels and reducing false positives around the optic disc and in regions of choroidal vessels and lesions. Quantitative results are provided, in which the penalization stage improves the segmentation precision segmentation by 11.84%, the recall by 12.98% and the accuracy by 0.40%. To facilitate further evaluation, usage, and algorithm comparison, the algorithm, the data set used, the ground truth, and the results are made available on the internet.

'The Microhand': a new concept of micro-forceps for ocular robotic surgery.

PURPOSE: To test the feasibility of retinal manipulations using a new micromanipulator (Microhand) for ocular robotic microsurgery. METHODS: Pneumatically actuated four-finger microhands were developed at UCLA with micro electromechanical systems (MEMS) technology to mimic a human hand for small object manipulation. Microhands with four 4 mm finger lengths were used for this study to lift caliper weights and fresh retinal tissue of porcine cadaver eyes to find the maximum force at a given pressure and feasibility of the microhands for retinal manipulation in real surgery. RESULTS: A full closure of the microhand used for caliper weight lifting was achieved under 65 psi (448 kPa) of air pressure. The four-fingered microhand was able to develop about 20 mN of total lifting force and 5 mN per finger at 80 psi (551 kPa), and was strong enough to displace and lift the retina of pig eyes. CONCLUSIONS: The microhand is able to apply calibrated forces to ocular tissues and is suitable for ocular microsurgical procedures. This new tool would be useful in the development of robotic microsurgery.

Robotic microsurgery: corneal transplantation.

BACKGROUND: Robotic ocular microsurgery including corneal suturing has been proven to be feasible in porcine eyes. AIM: To determine whether or not bimanual teleoperated robotic penetrating keratoplasty (PK) can be performed in porcine and human eyes. METHODS: Three arms of the da Vinci surgical robot were loaded with a dual-channel video and two, 360 degrees -rotating, 8 mm, wrested-end effector instruments and placed over porcine eyes or over a human cadaver head. The surgeon remotely performed mechanical trephination, cardinal sutures, continuous 10.0 nylon sutures and suture adjustments on both eyes. The procedures were documented with still and video photography. RESULTS: Using the da Vinci robot, penetrating keratoplasty procedures were successfully performed on both porcine eyes and human eyes in natural anatomical conditions. The precise placement of continuous sutures was facilitated by the wrested-end forceps. Orbital rims and nose did not limit surgical motions. CONCLUSION: Teleoperated robotic penetrating keratoplasty is technically feasible in humans. Further studies are pending to implement the procedure with femtosecond laser and other automated steps.

Combined 25- and 23-gauge surgery: a new sutureless vitrectomy technique.

The 25- and 23-gauge sutureless vitrectomy techniques decrease the surgical trauma and improve patients' postoperative comfort. The disadvantages of the 25-gauge system include pliable instrument and slower gel removal. The 23-gauge system provides faster speed of vitrectomy and the instruments have stiffer shafts, but it requires a larger incision. To circumvent some of these limitations, a new sutureless transconjunctival vitrectomy technique that combines 23- and 25-gauge cannulas and instruments was studied. Fifty-three patients underwent vitreoretinal surgery using two 25-gauge ports for the infusion and light probe and one 23-gauge port for the vitreous cutter and various instruments. No intraoperative or postoperative complications were noted and no cases required conversion to another technique.

[Comparison of different vitrectomy systems]. / Comparaison des différents systèmes de vitrectomie.

INTRODUCTION: The vitrectomy systems in use today have greatly improved from a technical point of view since the introduction of this surgical technique in the 1970s. The TSV 25 (Transconjunctival Standard vitrectomy) using 25-gauge vitrectomy probes and the high-speed vitrectomy module is one of the latest significant advances. This new system does a complete vitrectomy without opening or closing the conjunctiva. MATERIAL AND METHOD: At the present time, three different aspiration modes (venturi, peristaltic and concentrix), two different probe diameters (20- and 25-gauge) and two cutting modes (pneumatic and high-speed) are available. The author assessed and compared the efficacy of the two different probe diameters and the two different cutting modes available with the venturi pump on the Millennium (Millennium Microsurgical system, Bausch & Lomb, Saint Louis, MO). RESULTS AND CONCLUSION: These estimates highlighted the better efficacy of the high-speed cutting mode in comparison to the pneumatical mode. Regarding the probe diameters, the 25-gauge probe is less efficient than the 20-gauge probe. Nevertheless, the flow difference between the two is minimal in comparison to its clinical benefit.

[Surgical follow-up and importance of information and consent on behalf of patients undergoing esthetic blepharoplasty]. / Suites opératoires et importance de l'information et du consentement éclairé des patients dans les blépharoplasties esthétiques.

INTRODUCTION: Plastic surgery of the eyelids aims to improve the cosmetic aspect while correcting either an excess of palpebral skin, or an orbital septum dehiscence with fat porf2p4on in the palpebral spaces, after evaluation of horizontal and vertical palpebral laxity. PATIENTS AND METHODS: The authors describe follow-up of upper and lower lid blepharoplasty by cutaneous and conjunctival approaches respectively, with case descriptions and a review of the literature. RESULTS: A "calendar" is made of the different phases of healings, to the final aesthetic aspect desired. DISCUSSION: The patients wishes as to technique and results of blepharoplasty must be discussed and understood. The surgeon must forewarn of eventual per and postoperative complications (hemorrhage, infection), but also the usual follow-up (hematoma, edema, scarring ...). This allows to avoid aggravation of the patients "legitimate" worrying when he/she looks in the mirror! CONCLUSION: The authors underline the importance of patient information concerning the pre and postoperative aspects of aesthetic blepharoplasty.

The short-wavelength mechanisms of Stiles in age-related macular degeneration.

Clinical measurements by the increment-threshold technique of W.S. Stiles are reported in five cases of age-related macular degeneration. Measurements were made on a modified Tübingen perimeter using 1 degree, short-wavelength targets presented on a red field.