Microscope-integrated Optical Coherence Tomography Research Articles

Glaucoma surgery experiments using digital microscope-integrated optical coherence tomography and OCT-compatible instruments

There is a certain failure rate in traditional glaucoma surgery because of the lack of depth information in microscope images. In this work, we present a digital microscope-integrated optical coherence tomography (MIOCT) system and several custom-made OCT-compatible instruments for glaucoma surgery. Sixteen ophthalmologists were asked to perform trabeculectomy and canaloplasty on live porcine eyes using the system and instruments. After surgery, a subjective feedback survey about the user experience was taken. The experiment results showed that our system can help surgeons easily locate important tissue structures during surgery. The custom-made instruments also solved the shadowing problem in OCT imaging. Surgeons preferred to use the system in their future practice.

Microscope-integrated optical coherence tomography for in vivo human brain tumor detection with artificial intelligence.

It has been shown that optical coherence tomography (OCT) can identify brain tumor tissue and potentially be used for intraoperative margin diagnostics. However, there is limited evidence on its use in human in vivo settings, particularly in terms of its applicability and accuracy of residual brain tumor detection (RTD). For this reason, a microscope-integrated OCT system was examined to determine in vivo feasibility of RTD after resection with automated scan analysis. Healthy and diseased brain was 3D scanned at the resection edge in 18 brain tumor patients and investigated for its informative value in regard to intraoperative tissue classification. Biopsies were taken at these locations and labeled by a neuropathologist for further analysis as ground truth. Optical OCT properties were obtained, compared, and used for separation with machine learning. In addition, two artificial intelligence-assisted methods were utilized for scan classification, and all approaches were examined for RTD accuracy and compared to standard techniques. In vivo OCT tissue scanning was feasible and easily integrable into the surgical workflow. Measured backscattered light signal intensity, signal attenuation, and signal homogeneity were significantly distinctive in the comparison of scanned white matter to increasing levels of scanned tumor infiltration (p < 0.001) and achieved high values of accuracy (85%) for the detection of diseased brain in the tumor margin with support vector machine separation. A neuronal network approach achieved 82% accuracy and an autoencoder approach 85% accuracy in the detection of diseased brain in the tumor margin. Differentiating cortical gray matter from tumor tissue was not technically feasible in vivo. In vivo OCT scanning of the human brain has been shown to contain significant value for intraoperative RTD, supporting what has previously been discussed for ex vivo OCT brain tumor scanning, with the perspective of complementing current intraoperative methods for this purpose, especially when deciding to withdraw from further resection toward the end of the surgery.

Visualization of Cataract Surgery Steps With 4D Microscope-Integrated Swept-Source Optical Coherence Tomography in Ex Vivo Porcine Eyes.

To investigate the visualization capabilities of high-speed swept-source optical coherence tomography (SS-OCT) in cataract surgery. Cataract surgery was simulated in wet labs with ex vivo porcine eyes. Each phase of the surgery was visualized with a novel surgical microscope-integrated SS-OCT with a variable imaging speed of over 1 million A-scans per second. It was designed to provide four-dimensional (4D) live-volumetric videos, live B-scans, and volume capture scans. Four-dimensional videos, B-scans, and volume capture scans of corneal incision, ophthalmic viscosurgical device injection, capsulorrhexis, phacoemulsification, intraocular lens (IOL) injection, and position of unfolded IOL in the capsular bag were recorded. The flexibility of the SS-OCT system allowed us to tailor the scanning parameters to meet the specific demands of dynamic surgical steps and static pauses. The entire length of the eye was recorded in a single scan, and unfolding of the IOL was visualized dynamically. The presented novel visualization method for fast ophthalmic surgical microscope-integrated intraoperative OCT imaging in cataract surgery allowed the visualization of all major steps of the procedure by achieving large imaging depths covering the entire eye and high acquisition speeds enabling live volumetric 4D-OCT imaging. This promising technology may become an integral part of routine and advanced robotic-assisted cataract surgery in the future. We demonstrate the visualization capabilities of a cutting edge swept-source OCT system integrated into an ophthalmic surgical microscope during cataract surgery.

Comparing Three-Dimensional Digitally Enabled Intraoperative OCT With Conventional Microscope-Integrated OCT in Vitreoretinal Surgery: A Post Hoc Analysis of the DISCOVER Study.

This study compared the surgeon experience between conventional microscope-integrated intraoperative optical coherence tomography (iOCT) and digitally enabled microscope-integrated iOCT in vitreoretinal surgery. This is a post hoc case-control analysis of the DISCOVER study. Conventional microscope-integrated iOCT (Rescan 700, Zeiss) was compared with digitally enabled iOCT (Artevo 800, Zeiss). Compared variables included surgical field-based visualization (ie, ocular heads-up display in the conventional group; three-dimensional screen-based visualization in the digital iOCT group) and non-surgical field-based visualization (ie, review on the external two-dimensional monitor). A total of 200 patients were included. Surgical field-based visualization of iOCT was significantly higher in the digitally enabled group (P < 0.0001). Required endoillumination level was significantly lower in the digital iOCT group (P < 0.0001). Surgeons reported "significant" back discomfort and headache more frequently when using conventional iOCT (P = 0.003 and P = 0.001, respectively). Digitally enabled iOCT resulted in greater surgical visualization efficiency, appeared to require a lower illumination level, and may provide advantages for ergonomic-related discomfort. [Ophthalmic Surg Lasers Imaging Retina 2024;55:270-277.].

NOVEL METHOD FOR VISUALIZING PERIPHERAL RETINAL STRUCTURES WITH MICROSCOPE-INTEGRATED OPTICAL COHERENCE TOMOGRAPHY.

Visualization of peripheral retinal structures with optical coherence tomography (OCT) can be challenging but can offer valuable clinical information. We describe a method for intraoperative OCT of the peripheral retina. An investigational microscope-integrated OCT system with real-time 4D volumetric imaging was used in conjunction with a Goldmann style mirrored contact lens intraoperatively to capture peripheral images in three patients. We identified retinoschisis, a retinal break, and areas of focal retinal detachment using our peripheral OCT method. Use of a Goldmann lens in conjunction with intraoperative OCT offers surgeons the ability to resolve peripheral pathology that cannot be easily evaluated with OCT otherwise.

Posterior Segment Optical Coherence Tomography in Uncooperative Paediatric Patients Using Exo-Illumination and Microscope-Integrated Optical Coherence Tomography.

To describe a non-invasive technique for the acquisition of retinal optical coherence tomography (OCT) scans in paediatric patients undergoing examination under general anaesthesia (EUA) using microscope-integrated OCT (MIOCT). Prospective observational study Methods and Material: The study included 10 paediatric patients undergoing EUA for posterior segment pathology. These patients underwent OCT using MIOCT. No sclerotomy was made during imaging. The fundus was externally illuminated with a 25 gauge endoilluminator probe placed at the limbus and directed towards the posterior pole to aid in image acquisition by MIOCT (exo-illumination). Imaging for all patients was done by two trained vitreoretinal surgeons independently. Acquisition time was recorded for each surgeon. Interobserver variability in acquisition time and image quality was assessed to estimate the reliability of the novel imaging technique. In nine cases (90%), MIOCT successfully imaged the posterior segment pathology while in one case (10%) of X-linked retinoschisis, it failed to detect an inner retinal break located anteriorly at the equator. The mean acquisition time for surgeons one and two was 211.75 ± 26.00 and 212.58 ± 23.47 seconds, respectively. There was no significant difference in total image acquisition time between the two surgeons (P = 1.0) and the findings of both surgeons were comparable for structural morphology. 4x4 mm-sized scans provided the best delineation in macular pathology, while a 16x16 mm scan size was best suited for localising the area of interest and post-equatorial pathology. Using this technique acquisition of posterior segment OCT scans can be achieved non-invasively, using exo-illumination and MIOCT in paediatric patients undergoing EUA.

Commentary: To evaluate the functional and anatomical outcomes for autologous retinal autograft with Finesse™ Flex Loop for failed macular holes.

Commentary: To evaluate the functional and anatomical outcomes for autologous retinal autograft with Finesse™ Flex Loop for failed macular holes.

Clinical comparison of manual and laser-cut corneal tunnel for intrastromal air injection in femtosecond laser-assisted deep anterior lamellar keratoplasty (DALK).

The most crucial step in deep anterior lamellar keratoplasty (DALK) is to achieve a bare Descemet's membrane. We aimed to assess a new femtosecond laser software that allows for a precise intrastromal tunnel creation for big bubble (BB) air injection using a real-time microscope-integrated optical coherence tomography. A retrospective review of 61 eyes of 61 patients with keratoconus. Before introducing the new software update, DALK was performed using a partial-assisted femtosecond laser (partial-thickness circular cut followed by a lamellar cut) with manual intrastromal tunnel creation (partial FS-DALK group). After the software update, the femtosecond laser created the intrastromal tunnel (full FS-DALK group). In the full FS-DALK group, the BB's formation was significantly higher (64.3% vs. 36.4%, p = 0.04), and surgery time was shorter (21.8 ± 5.1 vs. 25.6 ± 6.8min, p = 0.025) than in the partial FS-DALK. Penetrating keratoplasty conversion rate (7.1% vs. 15.1%, p = 0.432) was similar between the groups. Both groups showed statistically significant improvement in uncorrected and corrected distance visual acuity, central corneal thickness, surface asymmetry, and regularity indices. Endothelial cell density loss at 12 and 18months was lower in the full compared with the partial FS-DALK group (12months:10.0% vs. 16; 18months: 10.7 vs. 16.5%, p < 0.001 for both comparisons). Creating the intrastromal guiding tunnel using FS laser for air injection resulted in a higher rate of BB formation, reduced long-term endothelial cell loss, and operating room time.

Application of Intraoperative Optical Coherence Tomography Technology in Anterior Segment Surgery.

The use of optical coherence tomography (OCT) technology in anterior segment diseases allows for precise assessment of the changes following anterior segment surgery. Advances in microscope-integrated OCT systems have allowed the utilization of intraoperative OCT (iOCT) in anterior segment surgeries, i.e., cornea, cataract, and refractive surgery. iOCT has enabled real-time precise visualization of anterior segment tissues as well as interactions between surgical instruments and ocular tissue; thus, the device can facilitate surgical procedures and provide valuable information for decision-making during anterior segment surgeries. In this review, the authors will introduce studies regarding the development of iOCT technology and its application in various anterior segment surgeries. Multiple studies have shown the efficacy of the iOCT for intraoperative assistance and guidance, suggesting the potential of the device for optimizing the surgical outcomes after cornea, cataract, and refractive surgery.

I-PDEK: Microscope-integrated OCT-assisted pre-Descemet endothelial keratoplasty.

Four patients with pseudophakic corneal edema were subjected to pre-Descemet endothelial keratoplasty (PDEK) under the direct guidance of microscope-integrated optical coherence tomography (i-OCT). i-OCT facilitated successful type 1 big bubble formation during donor preparation, debridement of the hypertrophic epithelium, planning and placement of surgical wounds, descemetorrhexis with removal of remnant Descemet membrane tags, and identification of correct donor orientation and interface details. It was also possible to discern the stability of intraocular lens, flat iris configuration, adequate stromal hydration, and wound apposition on i-OCT. Preoperative visual acuity was counting fingers (50%), 0.78 logMAR (25%), and 1.48 logMAR (25%), whereas postoperative visual acuity was 0.6 logMAR (50%) and 0.3 logMAR (50%). At 6-months of follow-up, all grafts were clear and well attached, the mean central corneal thickness, graft size, graft thickness, and endothelial cell loss were 557.25 ± 13.45 μm, 7.75 ± 0.20 mm, 25.5 ± 2.64 μm, and 21.6 ± 0.02%, respectively. To conclude, i-OCT helped during various surgical steps of PDEK.

Choroideremia Gene Therapy.

Choroideremia Gene Therapy.

Microscope Integrated Optical Coherence Tomography Guided Descemet Stripping Automated Endothelial Keratoplasty in Congenital Hereditary Endothelial Dystrophy.

PurposeTo describe the outcomes of descemet stripping automated endothelial keratoplasty (DSAEK) in congenital hereditary endothelial dystrophy (CHED) and to evaluate the role of microscope integrated optical coherence tomography (Mi-OCT) during the surgery.DesignRetrospective data analysis.MethodsA retrospective study from the medical records of all those patients who were diagnosed with CHED and underwent DSAEK at our centre from 2015 were evaluated. All patients underwent Mi-OCT-guided standard DSAEK procedure. Intra-operative difficulties, visual outcomes and graft survival were recorded.ResultsA total of 48 eyes of 29 patients with a mean age of 9.87 ± 8.2 years and mean follow-up of 17.3 months were evaluated. Thirty-nine eyes underwent primary DSAEK and 9 eyes underwent PKP. Three eyes who underwent PKP had failed graft for which they underwent DSAEK. The mean preoperative Snellen’s visual acuity was 1.71 ± 0.66 and the mean preoperative central corneal thickness was 1.10 ± 0.174 mm. Intraoperatively, all the grafts were attached which was confirmed using Mi-OCT. Graft detachment was seen in the immediate postoperative period in 10.4% (4 eyes) of primary DSAEK, out of which DM scoring was not performed in 2 eyes. Following DSAEK, cornea cleared at four-week follow-up in 89.7% eyes and in all the eyes the cornea cleared at six-week follow-up.ConclusionPrimary DSAEK could be a preferred option over PKP for CHED with early presentation and in those eyes with failed primary PKP. Mi-OCT is a very useful tool in these eyes for various intraoperative procedures, thereby improving the outcomes of the procedure.

Microscope-Integrated OCT-Guided Volumetric Measurements of Subretinal Blebs Created by a Suprachoroidal Approach.

PurposeTo investigate the use of imaging modalities in the volumetric measurement of the subretinal space and examine the volume of subretinal blebs created by a subretinal drug delivery device utilizing microscope-integrated optical coherence tomography (MIOCT).MethodsAn MIOCT image-based volume measurement method was developed and assessed for accuracy and reproducibility by imaging ceramic spheres of known size that were surgically implanted into ex vivo porcine eyes. This method was then used to measure subretinal blebs created in 10 porcine eyes by injection of balanced salt solution utilizing a subretinal delivery device via a suprachoroidal cannula. Bleb volumes obtained from MIOCT were compared to the intended injection volume.ResultsValidation of image-based volume measurements of ceramic spheres showed accuracy to ±0.029 µL (5.6%) for objects imaged over the posterior pole and ±0.025 µL (4.8%) over peripheral retina. The mean expected injection volume from extraocular tests of the suprachoroidal cannula was 66.44 µL (σ = 2.4 µL). The mean injection volume as measured by the MIOCT imaging method was 54.8 µL (σ = 12.3 µL), or 82.48% of expected injection volume.ConclusionsMIOCT can measure the volume of subretinal blebs with accuracy and precision. The novel suprachoroidal approach using a subretinal delivery device was able to deliver greater than 80% of expected injection volume into the subretinal space, as assessed by MIOCT.Translational RelevanceMIOCT provides a method for visualization, and analysis of images enables surgeons to quantify and evaluate the success of subretinal drug delivery via a suprachoroidal approach.

Quantitative Analysis of Gap Between the Intraocular Lens and Posterior Capsule Using Microscope-Integrated Optical Coherence Tomography in Eyes Undergoing Phacoemulsification.

PurposeTo quantitatively analyze the dimensions of the gap between the intraocular lens (IOL) and the posterior capsule using microscope-integrated optical coherence tomography (MIOCT).SettingInstitutional.DesignProspective, interventional.MethodsA total of 105 eyes of 105 consecutive patients planned for phacoemulsification with IOL implantation were enrolled. At the end of surgery, the gap between the IOL and the posterior capsule (IOL-PC gap) was measured using MIOCT (RESCAN). The same gap was reassessed at 1 week follow-up visit using the Visante-OCT system. The cases were sub-grouped based on the grade of cataract, IOL material, size and design and were analyzed to look for any difference in the IOL-PC gap both intraoperatively and postoperatively.ResultsThe IOL-PC gap could be successfully measured intra-operatively in all cases, using the RESCAN. The mean gap at the end of phacoemulsification was 385.08±264.58 µm, and at one week follow up this was 120.83± 95.13 µm.ConclusionMIOCT may be successfully used to quantify the dimensions of the gap between the IOL and the posterior capsule. It can be used as a potential tool to further understand the dynamics of the IOL-PC space and to assess the impact of various IOL and non-IOL parameters implicated in the causation of posterior capsule opacification.

Microscope integrated optical coherence tomography system combined with augmented reality.

One of the disadvantages in microscope-integrated optical coherence tomography (MI-OCT) systems is that medical images acquired via different modalities are usually displayed independently. Hence, surgeons have to match two-dimensional and three-dimensional images of the same operative region subjectively. In this paper, we propose a simple registration method to overcome this problem by using guided laser points. This method combines augmented reality with an existing MI-OCT system. The basis of our idea is to introduce a guiding laser into the system, which allows us to identify fiducials in microscopic images. At first, the applied voltages of the scanning galvanometer mirror are used to calculate the fiducials' coordinates in an OCT model. After gathering data at the corresponding points' coordinates, the homography matrix and camera parameters are used to superimpose a reconstructed model on microscopic images. After performing experiments with artificial and animal eyes, we successfully obtain two-dimensional microscopic images of scanning regions with depth information. Moreover, the registration error is 0.04 mm, which is within the limits of medical and surgical errors. Our proposed method could have many potential applications in ophthalmic procedures.

A case of old total Descemet membrane detachment due to ophthalmic viscosurgical device with clear cornea

We report a case of a large bullous descemet membrane detachment (DMD) following inadvertent injection of ophthalmic viscoelastic device in the supradescemetic space. A 27 years old male with juvenile open-angle glaucoma underwent trabeculectomy in the right eye followed by anterior chamber reformation. He developed DMD for which intracameral gas injection failed twice. He presented with complaints of blurring of images in that eye. Examination revealed a bullous DMD without any corneal edema, confirmed by anterior segment optical coherence tomography (ASOCT). Microscope-integrated intraoperative OCT (mi-OCT) guided drainage with intracameral gas injection was done following which the detachment settled completely.

Pediatric Vitreoretinal Surgery and Integrated Intraoperative Optical Coherence Tomography.

Intraoperative portable handheld and microscope-integrated OCT enhance the pediatric vitreoretinal surgeon's diagnostic abilities during examination under anesthesia and surgery, particularly in children who are challenging to examine preoperatively due to young age or ocular trauma. Improved OCT-guided visualization of vitreoretinal anatomic relationships has the potential to improve surgical safety and efficiency. In retinopathy of prematurity and other pediatric retinal vascular conditions, intraoperative OCT can be critical for distinguishing between retinoschisis and retinal detachment and highlighting abnormalities of the vitreoretinal interface that may contribute to development of tractional retinal detachments. During retinal detachment repair, intraoperative OCT aids identification of subtle retinal breaks, residual subretinal fluid, retained perfluorocarbon, preretinal membranes, and residual hyaloid, among other findings. In macular surgery, intraoperative OCT has demonstrated value in confirming completion or lack thereof of epiretinal and internal limiting membrane peeling and differentiating between lamellar and full-thickness macular holes. OCT-guided subretinal bleb formation and genetic vector delivery are critical to ensuring accurate localization of subretinal gene delivery for inherited retinal degenerations. Research on development of OCT-compatible surgical instruments, real-time three-dimensional volumetric OCT imaging, and integration with intraoperative OCT angiography are anticipated to further increase the utility of intraoperative OCT in pediatric vitreoretinal surgical decision-making.

Feasibility of microscope-integrated swept-source optical coherence tomography in canaloplasty.

BackgroundSeveral researchers have used commercial microscope-integrated optical coherence tomography (OCT) systems in glaucoma surgery, including ab interno trabeculectomy and canaloplasty. However, the 840 nm wavelength light source of the OCT systems is not ideal for imaging the anterior chamber angle structures because of its limited penetration. We evaluated the potential value of a microscope-integrated swept-source OCT system with a 1,310 nm center-wavelength light in canaloplasty for glaucoma.MethodsSixteen porcine eyes were used to simulate canaloplasty. The critical surgical steps were monitored using a prototype microscope-integrated OCT system with a 1,310 nm light source and a high axial scan rate of 100 kHz. The images from swept-source OCT and three-dimensional images from the microscope were projected simultaneously onto a liquid crystal display three-dimensional monitor (LMD-4251TD, Sony, Japan). The changes in the collector vessel (aqueous drainage structure in the porcine eye, similar to Schlemm’s canal in humans) were measured using Image J software. Histological sections stained with hematoxylin and eosin were used to assess surgical efficacy.ResultsHigh-resolution real-time images of the anterior segment were acquired during canaloplasty using the microscope-integrated OCT system. With the real-time OCT images, the position of the collector vessel was identified and the scleral flap could be created at the ideal location. The expansion of the collector vessel after viscoelastic injection was also visualized in real time. Compared with baseline, there was a significant increase in the cross-sectional area (from 14,502.98±9,242.55 to 59,499.04±20,506.41 µm2, P<0.001) of the collector vessel.ConclusionsUsing the microscope-integrated OCT system, real-time images of the anterior segment were successfully acquired during the operation. The microscope-integrated OCT system might be useful in future anti-glaucoma surgery.

INTRAOPERATIVE OPTICAL COHERENCE TOMOGRAPHY (OCT) GUIDANCE OF VITREORETINAL SURGERY

Background: Multiple studies have described the utility of intraoperative spectral-domain OCT (SD-OCT) with two dimensional (2D) B-scan imaging in the management of numerous vitreoretinal disorders including macular holes, vitreomacular traction disorders, epiretinal membranes and retinal detachment. Some of these studies also described post-processing of the 2D B-scans to obtain 3D images. With the advancement of intraoperative OCT technology, live volumetric (4D, i.e. 3D over time) visualization of different anterior and posterior segment surgeries has been described in recent studies using intraoperative swept-source microscope-integrated OCT (SS-MIOCT). Our study aims to explore the potential utility of SS-MIOCT during vitrectomy for complications of proliferative diabetic retinopathy. Aim of the work: To evaluate the use of live volumetric (4D) intraoperative swept-source microscope-integrated OCT (SS-MIOCT) in vitrectomy for proliferative diabetic retinopathy (PDR) complications.Patient and Methods: In this prospective study, we analyzed a subgroup of cases with PDR complications that required vitrectomy and that were imaged by the research SS-MIOCT system. In near real time, images were displayed in stereo heads-up display facilitating intraoperative surgeon feedback. Postoperative review included scoring image quality, identifying different diabetic retinopathy (DR)-associated pathologies and reviewing the intraoperatively documented surgeon feedback.Results: Twenty eyes were included. Indications for vitrectomy were tractional retinal detachment (TRD, 16 eyes), combined tractional-rhegmatogenous retinal detachment (2 eyes) and vitreous hemorrhage (2 eyes). Useful, good quality 2D (B-scans) and 4D images were obtained in 16/20 eyes (80%). In these eyes, multiple DR pathologies could be imaged. SS-MIOCT provided surgical guidance, e.g. in identifying dissection planes under fibrovascular membranes, and in determining residual membranes and traction that would benefit from additional peeling. In 4/20 eyes (20%) acceptable images were captured, but they were not useful due to high TRD elevation which was challenging for imaging.Conclusion: SS-MIOCT can provide important guidance during surgery for PDR complications through intraoperative identification of different pathologies and facilitation of intraoperative decision making.

Lightweight Learning-Based Automatic Segmentation of Subretinal Blebs on Microscope-Integrated Optical Coherence Tomography Images

Subretinal injections of therapeutics are commonly used to treat ocular diseases. Accurate dosing of therapeutics at target locations is crucial but difficult to achieve using subretinal injections due to leakage, and there is no method available to measure the volume of therapeutics successfully administered to the subretinal location during surgery. Here, we introduce the first automatic method for quantifying the volume of subretinal blebs, using porcine eyes injected with Ringer's lactate solution as samples. Ex vivo animal study. Microscope-integrated optical coherence tomography was used to obtain 3D visualization of subretinal blebs in porcine eyes at Duke Eye Center. Two different injection phases were imaged and analyzed in 15 eyes (30 volumes), selected from a total of 37 eyes. The inclusion/exclusion criteria were set independently from the algorithm-development and testing team. A novel lightweight, deep learning-based algorithm was designed to segment subretinal bleb boundaries. A cross-validation method was used to avoid selection bias. An ensemble-classifier strategy was applied to generate final results for the test dataset. The algorithm performs notably better than 4 other state-of-the-art deep learning-based segmentation methods, achieving an F1 score of 93.86 ± 1.17% and 96.90 ± 0.59% on the independent test data for entry and full blebs, respectively. The proposed algorithm accurately segmented the volumetric boundaries of Ringer's lactate solution delivered into the subretinal space of porcine eyes with robust performance and real-time speed. This is the first step for future applications in computer-guided delivery of therapeutics into the subretinal space in human subjects.