Real-time Optical Coherence Tomography Research Articles

Lifelong Changes in the Choroidal Thickness, Refractive Status, and Ocular Dimensions in C57BL/6J Mouse.

To investigate the changes in choroidal thickness (ChT), refractive status, and ocular dimensions in the mouse eye in vivo using updated techniques and instrumentation. High-resolution swept-source optical coherence tomography (SS-OCT), eccentric infrared photoretinoscopy, and custom real-time optical coherence tomography were used to analyze choroidal changes, refractive changes and ocular growth in C57BL/6J mice from postnatal day (P) 21 to month 22. The ChT gradually increased with age, with the thickest region in the para-optic nerve head and thinning outward, and the temporal ChT was globally thicker than the nasal ChT. Retinal thickness remained stable until 4months and subsequently decreased. The average spherical equivalent refraction error was -4.81 ± 2.71 diopters (D) at P21, which developed into emmetropia by P32, reached a hyperopic peak (+5.75±1.38D) at P82 and returned to +0.66 ± 1.86 D at 22months. Central corneal thickness, anterior chamber depth, lens thickness, and axial length (AL) increased continuously before 4months, but subsequently exhibited subtle changes. Vitreous chamber depth decreased with lens growth. ChT was correlated significantly with the ocular parameters (except for retinal thickness) before the age of 4months, but these correlations diminished after 4months. Furthermore, for mice younger than 4months, the difference in the ChT, especially temporal ChT, between the two eyes contributed most to that of axial length and spherical equivalent refraction error. Four months could be a watershed age in the growth of mouse eyes. Large-span temporal recordings of refraction, ocular dimensions, and choroidal changes provided references for the study of the physiological and pathological mechanisms responsible for myopia.

Optical Coherence Tomography as a Diagnosis-Assisted Tool for Guiding the Treatment of Melasma: A Case Series Study.

Background/Objectives: Multiple underlying pathomechanisms may lead to melasma, but there has been no report on the use of optical coherence tomography (OCT) to reveal specific pathomechanisms in individual patients and provide individualized treatments accordingly. Using real-time OCT images, we studied the pathomechanisms of melasma in 12 female patients and the effects of individualized treatments. Methods: Patients were divided into good and bad improved groups according to the improvement in hyperpigmentation at month 4. Results: In the bad improved group, all melanin or confetti melanin had significantly decreased at month 2 or month 4 while granular melanin ratio at month or month 4 significantly increased, the most parameters of dendritic-sharped cells (DCs) before and after treatment were not significantly different, the collagen area or collagen density at month 4 significantly decreased. In the good improved group, there was slightly low all melanin/confetti melanin at month 4 and high granular melanin at month 4 in comparison to the bad improved group. Moreover, most of the parameters in the DCs at month 4 significantly increased while most parameters in collagen at month 4 significantly decreased. Conclusions: OCT is useful in revealing the involved pathomechanisms of melasma in individualized patients. Positive treatment results can be achieved through individualized therapy regimen targeting the pathomechanisms.

Large area kidney imaging for pre-transplant evaluation using real-time robotic optical coherence tomography

Optical coherence tomography (OCT) can be used to image microstructures of human kidneys. However, current OCT probes exhibit inadequate field-of-view, leading to potentially biased kidney assessment. Here we present a robotic OCT system where the probe is integrated to a robot manipulator, enabling wider area (covers an area of 106.39 mm by 37.70 mm) spatially-resolved imaging. Our system comprehensively scans the kidney surface at the optimal altitude with preoperative path planning and OCT image-based feedback control scheme. It further parameterizes and visualizes microstructures of large area. We verified the system positioning accuracy on a phantom as 0.0762 ± 0.0727 mm and showed the clinical feasibility by scanning ex vivo kidneys. The parameterization reveals vasculatures beneath the kidney surface. Quantification on the proximal convoluted tubule of a human kidney yields clinical-relevant information. The system promises to assess kidney viability for transplantation after collecting a vast amount of whole-organ parameterization and patient outcomes data.

Real-time imaging and quantitative analysis of internal gap formation in bulk-fill and conventional resin composites: An OCT evaluation

BackgroundThis study used optical coherence tomography (OCT) to observe real-time internal gap formation in both bulk-fill and conventional resin composites. It aimed to provide a quantitative analysis of variations, addressing the inconclusive nature of microleakage assessment caused by differences in testing methods. MethodsFifty extracted third molars prepared with Class I cavities, were divided into five groups (n = 10). Conventional resin Filtek Z350 XT (FZX) was applied with a double-layer filling of 2 mm per layer. Bulk-fill resins X-tra fil (XTF), Filtek Bulk Fill Posterior Restorative (FBP), Surefil SDR Flow + (SDR), and Filtek Flowable Restorative (FFR) were applied with a single-layer filling of 4 mm. Real-time OCT imaging was conducted during light curing. Post-curing, the entire sample was OCT-scanned. Following this, ImageJ software was used to measure the gap (G1 %). Subsequently, thermal cycling (TC) (5000 times, 5 °C–55 °C) was applied, followed by OCT scanning to calculate the gap (G2 %) and ΔG%. Data were analyzed using two-way repeated measures ANOVA, Kruskal-Wallis test, and Duncan's test (α=0.05). ResultsThere was no significant difference in G1 % among the groups (p > 0.05). Following TC, FZX exhibited the highest G2 %, succeeded by FFR, FBP, XTF, and SDR, with SDR demonstrating the lowest G2 % (p < 0.05). FZX showed the highest ΔG% (p < 0.05), while SDR exhibited the lowest ΔG% (p < 0.05). ConclusionOCT proves to be a promising tool for detecting microleakage. TC exerted a more significant negative impact on conventional resin. Surefil SDR Flow + displayed the least microleakage, both before and after TC.

Distal planar rotary scanner for endoscopic optical coherence tomography.

Optical coherence tomography (OCT) is becoming a more common endoscopic imaging modality for detecting and treating disease given its high resolution and image quality. To use OCT for 3-dimensional imaging of small lumen, embedding an optical scanner at the distal end of an endoscopic probe for circumferential scanning the probing light is a promising way to implement high-quality imaging unachievable with the conventional method of revolving an entire probe. To this end, the present work proposes a hollow and planar micro rotary actuator for its use as an endoscopic distal scanner. A miniaturized design of this ferrofluid-assisted electromagnetic actuator is prototyped to act as a full 360° optical scanner, which is integrated at the tip of a fiber-optic probe together with a gradient-index lens for use with OCT. The scanner is revealed to achieve a notably improved dynamic performance that shows a maximum speed of 6500rpm, representing 325% of the same reported with the preceding design, while staying below the thermal limit for safe in-vivo use. The scanner is demonstrated to perform real-time OCT using human fingers as live tissue samples for the imaging tests. The acquired images display no shadows from the electrical wires to the scanner, given its hollow architecture that allows the probing light to pass through the actuator body, as well as the quality high enough to differentiate the dermis from the epidermis while resolving individual sweat glands, proving the effectiveness of the prototyped scanner design for endoscopic OCT application.

Real-time line-field optical coherence tomography for cellular resolution imaging of biological tissue.

A real-time line-field optical coherence tomography (LF-OCT) system is demonstrated with image acquisition rates of up to 5000 B-frames or 2.5 million A-lines per second for 500 A-lines per B-frame. The system uses a high-speed low-cost camera to achieve continuous data transfer rates required for real-time imaging, allowing the evaluation of future applications in clinical or intraoperative environments. The light source is an 840 nm super-luminescent diode. Leveraging parallel computing with GPU and high speed CoaXPress data transfer interface, we were able to acquire, process, and display OCT data with low latency. The studied system uses anamorphic beam shaping in the detector arm, optimizing the field of view and sensitivity for imaging biological tissue at cellular resolution. The lateral and axial resolution measured in air were 1.7 µm and 6.3 µm, respectively. Experimental results demonstrate real-time inspection of the trabecular meshwork and Schlemm's canal on ex vivo corneoscleral wedges and real-time imaging of endothelial cells of human subjects in vivo.

Real-time OCT feedback-controlled RPE photodisruption in ex vivo porcine eyes using 8 microsecond laser pulses.

Selective retinal pigment epithelium (RPE) photodisruption requires reliable real-time feedback dosimetry (RFD) to prevent unwanted overexposure. In this study, optical coherence tomography (OCT) based RFD was investigated in ex vivo porcine eyes exposed to laser pulses of 8 µs duration (wavelength: 532 nm, exposure area: 90 × 90 µm2, radiant exposure: 247 to 1975 mJ/µm2). For RFD, fringe washouts in time-resolved OCT M-scans (central wavelength: 870 nm, scan rate: 85 kHz) were compared to an RPE cell viability assay. Statistical analysis revealed a moderate correlation between RPE lesion size and applied treatment energy, suggesting RFD adaptation to inter- and intraindividual RPE pigmentation and ocular transmission.

OCTSharp: an open-source and real-time OCT imaging software based on C.

Optical coherence tomography (OCT) demands massive data processing and real-time displaying during high-speed imaging. Current OCT imaging software is predominantly based on C++, aiming to maximize performance through low-level hardware management. However, the steep learning curve of C++ hinders agile prototyping, particularly for research purposes. Moreover, manual memory management poses challenges for novice developers and may lead to potential security issues. To address these limitations, OCTSharp is developed as an open-source OCT software based on the memory-safe language C#. Within the managed C# environment, OCTSharp offers synchronized hardware control, minimal memory management, and GPU-based parallel processing. The software has been thoroughly tested and proven capable of supporting real-time image acquisition, processing, and visualization with spectral-domain OCT systems equipped with the latest advanced hardware. With these enhancements, OCTSharp is positioned to serve as an open-source platform tailored for various applications.

The State of Intraoperative OCT in Vitreoretinal Surgery: Recent Advances and Future Challenges.

Since its first introduction more than 30 years ago, optical coherence tomography (OCT) has revolutionized ophthalmology practice, providing a non-invasive in vivo cross-sectional view of the structures of the eye. Mostly employed in the clinical setting due to its tabletop configuration requiring an upright patient positioning, the recent advent of microscope-integrated systems now allows ophthalmologists to perform real-time intraoperative OCT (iOCT) during vitreoretinal surgical procedures. Numerous studies described various applications of this tool, such as offering surgeons feedback on tissue-instrument interactions in membrane peeling, providing structural images in macular hole repair, and showing residual subretinal fluid or perfluorocarbon in retinal detachment surgery. This narrative review aims at describing the state of the art of iOCT in vitreoretinal procedures, highlighting its modern role and applications in posterior segment surgery, its current limitations, and the future perspectives that may improve the widespread adoption of this technology.

Impact of real-time optical coherence tomography and angiographic coregistration on the percutaneous coronary intervention strategy.

The use of optical coherence tomography (OCT) with angiographic coregistration (ACR) during percutaneous coronary intervention (PCI) for procedural decision-making is evolving; however, large-scale data in real-world practice are lacking. Our study aims to evaluate the real-time impact of OCT-ACR on clinician decision-making during PCI. Patients with angiographic diameter stenosis >70% in at least one native coronary artery were enrolled in the study. The pre- and post-PCI procedural strategies were prospectively assessed after angiography, OCT, and ACR. Atotal of 500 patients were enrolled in the study between November 2018 and March 2020. Among these, data related to 472 patients with 483 lesions were considered for analysis. Preprocedural OCT resulted in achange in PCI strategy in 80% of lesions: lesion preparation (25%), stent length (53%), stent diameter (36%), and device landing zone (61%). ACR additionally impacted the treatment strategy in 34% of lesions. Postprocedural OCT demonstrated underexpansion (15%), malapposition (14%), and tissue/thrombus prolapse (7%), thereby requiring further interventions in 30% of lesions. No further change in strategy was observed with subsequent postprocedural ACR. Angiographic and procedural success was achieved in 100% of patients, and the overall incidence of major adverse cardiovascular events at 1 year was 0.85%. The outcomes reflect the real-time impact of OCT-ACR on the overall procedural strategy in patients undergoing PCI. ACR had asignificant impact on the treatment strategy and was associated with better clinical outcomes at 1 year after index PCI. OCT-ACR has become apractical tool for improving outcomes in patients with complex lesions.

Self Distillation for Improving the Generalizability of Retinal Disease Diagnosis Using Optical Coherence Tomography Images

Optical coherence tomography (OCT) imaging has become a point-of-care imaging modality for the diagnosis of retinal diseases. Varying speckle noise in the OCT images across datasets and scanners worsens the performance of existing artificial intelligence (deep learning) models, that have been trained mostly with images having a particular noise level. The existing deep learning models for predicting retinal diseases are heavy, requires a sophisticated computing environment to train and deploy. Generalized lightweight deep learning models that can provide an automated diagnosis on an edge platform are highly appealing in the clinic. This work proposes a self distillation framework based on lightweight deep learning models for building generalizable deep models for retinal disease diagnosis. The proposed approach with three different baseline models ResNet18, MobileNetV2 and ShuffleNetV2, has been validated on simulated and real-time noisy OCT B-scans spanning a range of SNRs from four OCT datasets. The proposed method significantly outperforms the existing methods with improvement (as high as 14%) in precision, accuracy, and F1-score, to show that the self distillation framework can provide more generalizability for automated retinal diagnosis.

Adaptability of melanocytes post ultraviolet stimulation in patients with melasma.

Dynamic in vivo changes in melanin in melasma lesions after exposure to ultraviolet (UV) irradiation have not been described. To determine whether melasma lesions and nearby perilesions demonstrated different adaptive responses to UV irradiation and whether the tanning responses were different among different locations on face. We collected sequential images from real-time cellular resolution full-field optical coherence tomography (CRFF-OCT) at melasma lesions and perilesions among 20 Asian patients. Quantitative and layer distribution analyses for melanin were performed using a computer-aided detection (CADe) system that utilizes spatial compounding-based denoising convolutional neural networks. The detected melanin (D) is melanin with a diameter >0.5 µm, among which confetti melanin (C) has a diameter of >3.3 µm and corresponds to a melanosome-rich package. The calculated C/D ratio is proportional to active melanin transportation. Before UV exposure, melasma lesions had more detected melanin (p = 0.0271), confetti melanin (p = 0.0163), and increased C/D ratio (p = 0.0152) in the basal layer compared to those of perilesions. After exposure to UV irradiation, perilesions have both increased confetti melanin (p = 0.0452) and the C/D ratio (p = 0.0369) in basal layer, and this effect was most prominent in right cheek (p = 0.030). There were however no significant differences in the detected, confetti, or granular melanin areas before and after exposure to UV irradiation in melasma lesions in all the skin layers. Hyperactive melanocytes with a higher baseline C/D ratio were noted in the melasma lesions. They were "fixed" on the plateau and were not responsive to UV irradiation regardless of the location on face. Perilesions retained adaptability with a dynamic response to UV irradiation, in which more confetti melanin was shed, mainly in the basal layer. Therefore, aggravating effect of UV on melasma was mainly due to UV-responsive perilesions rather than lesions.

Anterior vitreous detachment and retrolental material during cataract surgery: incidence and risk factors, with pathological evidence.

To determine the incidence of anterior vitreous detachment (AVD) and retrolental material occurrence in cataract surgery, determine the influence of surgical factors on it, and confirm the source of the material. Affiliated Hospital of Nantong University, Jiangsu Province, China. Prospective single-center study. Age, sex, ocular complication, nuclear sclerosis grade, ultrasonic time, mean longitudinal power, cumulative dissipated energy (CDE), total aspiration time, and estimated fluid usage were recorded for each patient. Retrolental anatomy was observed before and during surgery using real-time optical coherence tomography integrated into a microscope. The eyes with AVD were carefully observed and recorded during illumination with an optical fiber. Retrolental material was stained using immunohistochemistry. 205 eyes from 205 patients were included in this study. Spontaneous AVD was found in 5 cases. Intraoperatively, AVD was identified in 115 eyes (56.1%). Retrolental material presence was observed in 75 eyes (36.6%). A logistic regression model showed that CDE and aspiration time had a statistically significant effect on AVD ( P < .05, 95% CI, 1.011-1.558; P < .05, 95% CI, 1.026-1.051), and CDE was positively correlated with retrolental material occurrence ( P < .05, 95% CI, 1.052-1.534). Samples from 5 cases expressed large amounts of αA- and βA-crystallins. Spontaneous AVD is rare in phakic eyes. There was a marked increase in AVD during surgery, with retrolental material occurring in more than a third of cases. Higher CDE and longer total aspiration time were risk factors for AVD. Immunohistochemistry revealed that most of the retrolental materials were lens fragments.

INTRAOPERATIVE OPTICAL COHERENCE TOMOGRAPHY FOR REAL-TIME VISUALIZATION OF THE POSITIONAL RELATIONSHIP BETWEEN BUCKLING MATERIAL AND RETINAL BREAKS DURING SCLERAL BUCKLING FOR RHEGMATOGENOUS RETINAL DETACHMENT

To report the usefulness of a new surgical method using intraoperative optical coherence tomography that can more accurately place the buckling material for scleral buckling using a noncontact wide-angle viewing system with a cannula-based chandelier endoilluminator for the treatment of rhegmatogenous retinal detachment. The medical records of 12 eyes of 11 patients with rhegmatogenous retinal detachment treated with scleral buckling combined with real-time intraoperative optical coherence tomography observation were retrospectively reviewed. Real-time observations of the positional relationship between the protrusion of buckling material and retinal breaks with intraoperative optical coherence tomography revealed that retinal breaks were not properly placed on the protrusion of the buckling material in five eyes, requiring the intraoperative repositioning of the buckling material. Eventually, the scleral buckling combined with real-time intraoperative optical coherence tomography observation yielded the initial anatomical success rates of 100% without noteworthy intraoperative or postoperative complications. This procedure is a novel approach that enables safer and more accurate placement of the buckling material and may contribute to improving the outcomes of scleral buckling in the future.

Bronchoscopic Journey of in vivo Real-Time Microscopic Imaging in ILD: A Case Series

Background: Patients with interstitial lung diseases (ILDs) frequently present with nondiagnostic high-resolution CT (HRCT) scan and bronchoalveolar lavage (BAL) results, resulting in the need for invasive surgical or cryo-lung biopsy that is associated with significant morbidity. Confocal laser endomicroscopy (CLE) and optical coherence tomography (OCT) are high-resolution laser and light-based techniques that provide real-time imaging of the alveolar compartment during bronchoscopy with a different depth and field of view. Objectives: The aim of the study was to correlate OCT and CLE imaging to HRCT imaging in ILD. Methods: This is a retrospective case series of 20 ILD patients who underwent alveolar CLE and OCT imaging during a standard bronchoscopy with BAL, followed by a lung biopsy when indicated. CLE and OCT imaging were compared to four main HRCT patterns and histology. The final diagnosis was based on the multidisciplinary discussion diagnosis. Results: Bronchoscopic CLE and OCT imaging were feasible and safe and provided additional high-detailed anatomical information compared to the HRCT. Bronchoscopic real-time CLE was capable of identification of “alveolar cells” (ground glass opacities) and lung fibrosis (increased alveolar elastin fibers). Bronchoscopic real-time OCT allowed for visualization of “patchy fibrotic disease”, “honeycombing” (microcysts), and mucosal granulomas in the airways. Conclusions: Bronchoscopic CLE and OCT of the alveolar compartment is feasible and safe and enables minimally invasive, high-resolution detection of specific ILD features with the potential to improve ILD diagnostics and monitoring and decrease the need for surgical or cryo-lung biopsies.

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.

Higher-order regression three-dimensional motion-compensation method for real-time optical coherence tomography volumetric imaging of the cornea.

.SignificanceOptical coherence tomography (OCT) allows high-resolution volumetric three-dimensional (3D) imaging of biological tissues in vivo. However, 3D-image acquisition can be time-consuming and often suffers from motion artifacts due to involuntary and physiological movements of the tissue, limiting the reproducibility of quantitative measurements.AimTo achieve real-time 3D motion compensation for corneal tissue with high accuracy.ApproachWe propose an OCT system for volumetric imaging of the cornea, capable of compensating both axial and lateral motion with micron-scale accuracy and millisecond-scale time consumption based on higher-order regression. Specifically, the system first scans three reference -mode images along the -axis before acquiring a standard C-mode image. The difference between the reference and volumetric images is compared using a surface-detection algorithm and higher-order polynomials to deduce 3D motion and remove motion-related artifacts.ResultsSystem parameters are optimized, and performance is evaluated using both phantom and corneal (ex vivo) samples. An overall motion-artifact error of microns and processing time of about 3.40 ms for each B-scan was achieved.ConclusionsHigher-order regression achieved effective and real-time compensation of 3D motion artifacts during corneal imaging. The approach can be expanded to 3D imaging of other ocular tissues. Implementing such motion-compensation strategies has the potential to improve the reliability of objective and quantitative information that can be extracted from volumetric OCT measurements.

Real-time OCT image denoising using a self-fusion neural network.

Optical coherence tomography (OCT) has become the gold standard for ophthalmic diagnostic imaging. However, clinical OCT image-quality is highly variable and limited visualization can introduce errors in the quantitative analysis of anatomic and pathologic features-of-interest. Frame-averaging is a standard method for improving image-quality, however, frame-averaging in the presence of bulk-motion can degrade lateral resolution and prolongs total acquisition time. We recently introduced a method called self-fusion, which reduces speckle noise and enhances OCT signal-to-noise ratio (SNR) by using similarity between from adjacent frames and is more robust to motion-artifacts than frame-averaging. However, since self-fusion is based on deformable registration, it is computationally expensive. In this study a convolutional neural network was implemented to offset the computational overhead of self-fusion and perform OCT denoising in real-time. The self-fusion network was pretrained to fuse 3 frames to achieve near video-rate frame-rates. Our results showed a clear gain in peak SNR in the self-fused images over both the raw and frame-averaged OCT B-scans. This approach delivers a fast and robust OCT denoising alternative to frame-averaging without the need for repeated image acquisition. Real-time self-fusion image enhancement will enable improved localization of OCT field-of-view relative to features-of-interest and improved sensitivity for anatomic features of disease.

Laser-integrated real-time OCT in anterior segment procedures.

Intraoperative optical coherence tomography (OCT) was so far only available as a microscope-integrated or handheld device. Recently, this technology has been integrated into a femtosecond (FS) laser. This pilot study analyzed the potential of intraoperative imaging using OCT during FS-assisted procedures of the anterior eye segment. Therefore, intraoperatively acquired videos using FS-integrated intraoperative OCT (laser-integrated [LI] OCT) in 14 patients (Victus, Bausch & Lomb) were analyzed in different surgical procedures. The results showed that all surgical steps could be successfully visualized by LI-OCT. LI-OCT added important information regarding the depth and location of the incisions and dissection planes. Moreover, dynamic processes could be observed in real-time. LI-OCT represents a new imaging technology that makes it possible to visualize intraoperative steps during FS-assisted surgery. In the future, automatic image analysis based on artificial intelligence could be helpful to detect complications at an early stage and to automatically stop the laser process in relevant constellations.

A novel method of tunnel creation using intraoperative optical coherence tomography-guided deep anterior lamellar keratoplasty.

The big bubble technique has become the technique of choice for performing deep anterior lamellar keratoplasty (DALK) since its inception in 2002. The main challenge with this technique is in achieving a big bubble while preventing inadvertent perforation of the Descemet’s membrane. Although femtosecond lasers have increased the safety, accuracy, and predictability of corneal dissection in DALK, the challenge of achieving a big bubble still exists. To overcome this challenge, Zeimer Z8 Femto LDV has launched a new software module for DALK, which has an added advantage of real-time optical coherence tomography–assisted femtosecond tunnel creation for achieving a big bubble.