Swept-source Optical Coherence Tomography Technology Research Articles

Axial length acquisition success rates and agreement of four optical biometers and one ultrasound biometer in eyes with dense cataracts

BackgroundTo evaluate the axial length acquisition success rates and agreement between various biometric parameters obtained with different biometers in dense cataracts.MethodsFifty-one eyes were measured using Anterion®, Argos® and IOLMaster® 700 swept-source optical coherence tomography (SS-OCT) biometers, a Pentacam® AXL partial coherence interferometry (PCI) biometer, and an OcuScan® RxP ultrasound biometer. We measured keratometry (K1, flattest keratometry and K2, steepest keratometry), white-to-white (WTW), anterior chamber depth (ACD), lens thickness (LT) and axial length. Cataracts were classified according to the Lens Opacities Classification System III grading system, the dysfunctional lens index (DLI) and Pentacam® nucleus staging (PNS) metrics. Percentage of acquisition success rate and a Bland–Altman analysis for the agreement between biometers were calculated.ResultsThe mean LOCS III score was 3.63 ± 0.92, the mean DLI was 2.95 ± 1.30 and the mean PNS was 2.36 ± 1.20. The acquisition success rates for the Anterion®, Argos®, IOLMaster® 700, Pentacam® AXL and OcuScan® RxP biometers were 94.12%, 100%, 98.04%, 60.78% and 100%, respectively. There were significant differences in the success rates between biometers (P = 0.014). There were statistically significant differences between biometers for all parameters evaluated (P < 0.05). The range of the limit of agreement (LoA) for all comparisons of K1 and K2 were > 1.00 D. The LoA for WTW ranged from 0.095 to 1.050 mm. The LoA for ACD and LT ranged from 0.307 to 0.114 mm and from 0.378 to 0.108 mm, respectively. The LoA for axial length ranged from 0.129 to 2.378 mm.ConclusionsAmong optical biometers, those based on SS-OCT technology are more successful at measuring axial length in eyes with dense cataracts.Trial Registration: The study was registered with the National Institutes of Health (clinical trial identifier NCT05239715, http://www.clinicaltrials.gov).

Dual-FBG bearing fault probe based on a CNN-LSTM-encoder network.

A centimeter-sized bearing fault probe based on dual-fiber Bragg grating vibration sensing is proposed. The probe can provide multi-carrier heterodyne vibration measurements based on swept source optical coherence tomography technology and the synchrosqueezed wavelet transform method to obtain a wider vibration frequency response range and collect more accurate vibration data. For the sequential characteristics of bearing vibration signals, we propose a convolutional neural network with long short-term memory and transformer encoder. This method is proven in bearing fault classification under variable working conditions, and the accuracy rate reaches 99.65%.

Swept-Source Optical Coherence Tomography-Based Biometry: A Comprehensive Overview

The purpose of this study was to summarize the results related to ocular biometry performed using swept-source optical coherence tomography (SS-OCT). A literature search was conducted to search articles reporting the clinical outcomes of patients who underwent examinations with commercially available SS-OCT machines. The available data were thoroughly analyzed, with a particular focus on all the biometric factors used to calculate the power of intraocular lenses (IOLs) implanted during cataract surgery. The agreement, repeatability, and reproducibility of several parameters among different devices were examined. The variations found for parameters obtained from agreement testing were evaluated in order to promote the interchangeability of devices. Swept-source optical coherence tomography biometers usually produce highly repeatable and reproducible results. The excellent results obtained led us to the conclusion that optical biometers based on SS-OCT technology will probably take the lead in ocular biometry.

Evaluation of intraoperative aphakic eye axial length measurements using swept-source OCT.

To evaluate intraoperative aphakic eye axial length (AL) measurements using swept-source optical coherence tomography (SS-OCT). Hanusch Hospital, Vienna, Austria. Prospective single-center study. Patients scheduled for cataract surgery were measured using SS-OCT (IOLMaster 700, Carl Zeiss Meditec AG) to assess the AL. Intraoperatively (intra-OP), SS-OCT measurements were performed with a prototype device (IOLMaster 700 connected to an OPMI Lumera 700 microscope, CZM) at the beginning of cataract surgery furthermore of the aphakic eye and 2 months after surgery. 106 patients were included. Of the 59 eyes of 59 patients, the phakic median AL preoperatively and intra-OP was 23.61 mm ± 0.96 (standard deviation [SD]) and 23.51 mm ± 0.96 (SD), respectively. The absolute median difference was 0.028 ± 0.02 (SD) (P = .049). Median phakic AL intra-OP vs 2 months postoperatively (post-OP) was 23.51 mm ± 0.97 (SD) vs 23.49 mm ± 0.95 (SD). The absolute median difference was 0.049 ± 0.04 (SD) (P = .000). Median AL intra-OP aphakic vs 2 months post-OP pseudophakic was 23.42 mm ± 0.97 (SD) vs 23.42 mm ± 0.97 (SD), respectively. Absolute median difference was 0.038 ± 0.04 (SD) (P = .379). Intra-OP, SS-OCT technology of the phakic and aphakic eye shows excellent comparability to preoperative and postoperative measurements. This technique allows AL measurements with high precision in cases in which preoperative biometric measurements are not possible.

Three-Dimensional Reconstruction and Swept-Source Optical Coherence Tomography for Crystalline Lens Tilt and Decentration Relative to the Corneal Vertex.

PurposeTo investigate crystalline lens tilt and decentration with respect to the corneal vertex (CV) using swept-source optical coherence tomography (SS-OCT) combined with three-dimensional (3D) reconstruction.MethodsThirty consecutive patients with cataract (30 right eyes) were included in this prospective, observational, pilot case series study. SS-OCT anterior segment images and 3D reconstructions were used for data analysis.ResultsThe mean distance between the central points of crystalline lens plane and limbus plane was approximately 0.33 ± 0.18 mm. The distance of the center of the limbus plane relative to the CV was approximately 0.31 ± 0.14 mm, which approximated the distance of the center of the crystalline lens plane relative to the CV at 0.33 ± 0.20 mm (P = 0.354). However, the centers of the limbus and crystalline planes were not in the same quadrant in 80% of eyes (24/30). Moreover, the crystalline lens tilted by approximately 4.16° ± 1.97° relative to the CV.ConclusionsThe center of the limbus plane was not consistent with that of the crystalline lens plane. The tilt and decentration of the crystalline lens were natural phenomena.Translational RelevanceThe SS-OCT technology combined with 3D reconstruction was useful for quantifying the tilt and decentration of the crystalline lens. The definition of angle alpha used for premium IOL screening should be updated.

Multi-MHz MEMS-VCSEL swept-source optical coherence tomography for endoscopic structural and angiographic imaging with miniaturized brushless motor probes.

Swept source optical coherence tomography (SS-OCT) enables volumetric imaging of subsurface structure. However, applications requiring wide fields of view (FOV), rapid imaging, and higher resolutions have been challenging because multi-MHz axial scan (A-scan) rates are needed. We describe a microelectromechanical systems vertical cavity surface-emitting laser (MEMS-VCSEL) SS-OCT technology for A-scan rates of 2.4 and 3.0 MHz. Sweep to sweep calibration and resampling are performed using dual channel acquisition of the OCT signal and a Mach Zehnder interferometer signal, overcoming inherent optical clock limitations and enabling higher performance. We demonstrate ultrahigh speed structural SS-OCT and OCT angiography (OCTA) imaging of the swine gastrointestinal tract using a suite of miniaturized brushless motor probes, including a 3.2 mm diameter micromotor OCT catheter, a 12 mm diameter tethered OCT capsule, and a 12 mm diameter widefield OCTA probe. MEMS-VCSELs promise to enable ultrahigh speed SS-OCT with a scalable, low cost, and manufacturable technology, suitable for a diverse range of imaging applications.

Ocular biometry with swept-source optical coherence tomography.

This study aimed to summarize the outcomes reported when swept-source optical coherence tomography (SS-OCT) is used for ocular biometry. A literature search was performed to identify publications reporting clinical outcomes of patients measured with commercial SS-OCT. Twenty-nine studies were included in this review. A comprehensive analysis of the available data was performed, focusing on parameters used for intraocular lens (IOL) power calculation in cataract surgery, including keratometry, central corneal thickness, white-to-white distance, anterior chamber depth, lens thickness, axial length, IOL power, and pupil diameter. Different metrics for repeatability, reproducibility, and agreement between devices were analyzed. In general, SS-OCT biometers provide excellent repeatability and reproducibility outcomes; however, the differences obtained for some parameters measured in agreement studies should be carefully analyzed to validate the interchangeability between devices. The good outcomes reported lead us to conclude that optical biometers based on SS-OCT technology are likely to become the gold standard for ocular biometry.

Developments in Contact Lens Imaging: New Applications of Optical Coherence Tomography

Optical coherence tomography (OCT) is a high-speed and non-contact optical imaging technology widely used for noninvasive cross-sectional imaging of biological objects. Two main OCT technologies have been developed: time domain and Fourier domain technologies. The latter can be further divided into spectral domain OCT, which uses a broadband light source and a spectrometer as a detector, and swept source OCT, which employs a quickly-rotating laser source. Advances in OCT technology have made it one of the most helpful devices in ophthalmic practice. Fourier OCT has revolutionized imaging of the posterior segment of the eye, as well as of anterior structures and has enhanced the ability to diagnose and manage patients. It provides high-resolution information about the tear film, contact lens (CL), a qualitative and quantitative assessment of the anterior eye that is important in contact lens fitting, and allows possible eye surface changes while wearing contact lenses to be monitored. Potential swept source OCT technology applications include industrial processes of lens design and quality control. In this paper, we describe clinical applications and outline a variety of multifunctional uses of OCT in the field of refractive error correction with contact lenses.

An Evaluation of the IOLMaster 700.

To evaluate the repeatability and reproducibility of the Carl Zeiss Meditec IOLMaster 700, which uses swept-source optical coherence tomography technology, along with its agreement with the IOLMaster 500 and Lenstar LS 900. In a clinical practice, complete measurements were taken on one eye of 100 subjects: 51 with cataracts and 49 with clear lenses. Three sets of measurements were taken by 3 operators with three different IOLMaster 700 units, and one operator took 3 measurements with the IOLMaster 500 and the Lenstar. A random-effects model of analysis of variance was used to estimate the repeatability and reproducibility. The 95% limits of agreement (95% LoA) were calculated for all comparisons. Comparing the IOLMaster 700 and IOLMaster 500 in cataract patients, 95% LoA were -0.01 to +0.06 mm for axial length, -0.44 to +0.27 D for corneal power, and -0.18 to +0.17 mm for anterior chamber depth. Comparing the IOLMaster 700 and Lenstar for corneal thickness and lens thickness yielded 95% LoA of -4 to +13 μm and -0.26 to +0.41 mm, respectively. The repeatability and reproducibility limits for the IOLMaster 700 were ±0.014 and ±0.023 mm for axial length; ±0.26 and ±0.27 D for corneal power; ±7 and ±11 μm for corneal thickness; ±0.02 and ±0.02 mm for anterior chamber depth; and ±0.02 and ±0.05 mm for lens thickness, respectively. There was good agreement between the IOLMaster 700 and comparator instruments and superior or equivalent precision. Some differences were noted, but not considered clinically meaningful.

Intraocular lens power calculation in 2019: The cutting edge

In today's world, with the developments in technology to measure ocular biometric parameters more accurately and the availability of sophisticated methods for intraocular lens (IOL) power calculation, cataract surgery has become no less than a refractive surgery. This along with free and easy access to information regarding the latest technology has heightened patient expectations. The demand for a spectacle-free life after cataract surgery is higher than ever. Newer advances in optical biometry, including swept-source optical coherence tomography technology, supplemented by the availability of highly accurate IOL power calculation formulae including ones that use artificial intelligence have the potential to enable surgeons to achieve near-perfect outcomes in majority of their patients. To hit the bull's eye as far as target refraction is concerned, it is necessary to understand the benefits and limitations of currently available cutting edge technology and formulae and apply them to the cataract surgery practice.

Actualización sobre alteraciones de función visual y espesores coriorretinianos en la enfermedad de Parkinson

Parkinson's disease (PD) is a neurodegenerative process that affects 7.5 million people around the world.Since 2004, several studies have demonstrated changes in various retinal layers in PD using optical coherence tomography (OCT). However, there are some discrepancies in the results of those studies. Some of them have correlated retinal thickness with the severity or duration of the disease, demonstrating that OCT measurements may be an innocuous and easy biomarker for PD progression. Other studies have demonstrated visual dysfunctions since early phases of the disease. Lastly, the most recent studies that use Swept Source OCT technology, have found choroidal thickness increase in PD patients and provide new information related to the retinal degenerative process in this disease.The aim of this paper is to review the literature on OCT and PD, in order to determine the altered retinal and choroidal parameters in PD and their possible clinical usefulness, and also the visual dysfunctions with higher impact in these patients.

New objective lens density quantification method using swept-source optical coherence tomography technology: Comparison with existing methods

To assess a new objective cataract grading method based on lens densitometry on swept-source optical coherence tomography (SS-OCT) scans provided by the IOLMaster700. Rothschild Foundation, Paris, France. Prospective case series. All patients consulting for cataract evaluation who provided their consent to participate in the study were included. A history of eye surgery, corneal or retinal disorders, and ocular dryness were exclusion criteria. The average lens densitometry was measured with SS-OCT scans using ImageJ software. The ocular scatter index (OSI) measured with a double-pass aberrometer (Optical Quality Analysis System), the Pentacam nucleus staging (hereafter referred to as nuclear staging) score, and mean nuclear staging were also measured and compared with the mean lens densitometry. One hundred ten eyes (51 with cataract and 59 controls) were included. The average lens densitometry measurements were repeatable (P=.99, analysis of variance). The repeatability limit was 2.50 pixel units. The average lens density was correlated with the OSI (r2=0.52, P<.01), nuclear staging score (r2=0.75, P<.01), and mean nuclear staging (r2=0.41, P<.01). An average lens density greater than 82.9 pixel units was the cutoff threshold for cataract, with a sensitivity of 73.9% and a specificity of 91.2%. The average lens density measured by SS-OCT was a repeatable and reliable objective cataract grading method. It was correlated with OSI measurement. If the average lens density was greater than 82.9 pixel units and the patient reported visual impairment, cataract surgery might be discussed.

Axial Length Measurement Failure Rates With Biometers Using Swept-Source Optical Coherence Tomography Compared to Partial-Coherence Interferometry and Optical Low-Coherence Interferometry

To compare a new swept-source optical coherence tomography (SSOCT)-based biometer (OA-2000) with the IOLMaster v5.4 (partial-coherence interferometry) and Aladdin (optical low-coherence interferometry) biometers in terms of axial length measurement and failure rate in eyes with cataract. Reliability study. A total of 377 eyes of 210 patients were scanned with the 3 biometers in a random order. For each biometer, the number of unobtainable axial length measurements was recorded and grouped as per the type and severity of cataract based on the Lens Opacities Classification System III by the same experienced ophthalmologist. The Bland-Altman limits-of-agreement (LoA) method was used to assess the agreement in axial length measurements between the 3 biometers. The failure rate was 0 eyes (0%) with the OA-2000, 136 eyes (36.07%) with the IOLMaster, and 51 eyes (13.53%) with the Aladdin. χ2 analyses indicated a significant difference in failure rate between all 3 devices (P < .001). Logistic regression analysis highlighted a statistically significant trend of higher failure rates with increasing severity of nuclear, cortical, and posterior subcapsular cataracts. Bland-Altman statistics indicated small mean differences and narrow LoA (OA-2000 vs IOLMaster-0.09 to 0.08mm; OA-2000 vs Aladdin-0.10 to 0.07mm; IOLMaster vs Aladdin-0.05 to 0.04mm). The OA-2000, a new SSOCT-based biometer, outperformed both the IOLMaster and Aladdin biometers in very advanced cataracts of various morphologies. The use of SSOCT technology may be the reason for the improved performance of the OA-2000 and may lead to this technology becoming the gold standard for the measurement of axial length.

Macular disease detection with a swept-source optical coherence tomography-based biometry device in patients scheduled for cataract surgery

To assess the sensitivity and specificity for detecting macular disease with a new optical biometry device with swept-source optical coherence tomography (SS-OCT) used before cataract surgery. Hanusch Hospital, Vienna, Austria. Consecutive case series. This study included patients with or without macular disease. All patients were scanned using the new biometry device (IOLMaster 700), which allows a 1.0mm central retinal scan using SS-OCT technology. Also, all eyes were assessed using a dedicated retinal OCT device (RTVue) onthe same day. Two experienced examiners and 1 ophthalmology resident graded all scans individually. Sensitivity and specificity for detecting macular disease were assessed, as were the receiver operating characteristic curves. Of the 125 eyes included, 5 were excluded from the analysis, 65 had a macular disease, and 55 were healthy. The sensitivity of the biometry device was moderate (between 42% and 68%), and the specificity was high (89% to 98%). Intraobserver reproducibility for assessing the biometry device was 88.3%. The biometry device with SS-OCT provided useful information concerning the macula, especially for intraretinal fluid and macular holes. However, it cannot replace a macular OCT device. None of the authors has a financial or proprietary interest in any material or method mentioned.

Swept-Source Optical Coherence Tomography Angio™ (Topcon Corp, Japan): Technology Review.

Optical coherence tomography (OCT) angiography (OCTA) is a novel, noninvasive, three-dimensional imaging technique that allows for the visualization of intravascular flow in the microvasculature. Swept-source OCT technology utilizes longer-wavelength infrared light than conventional spectral-domain OCT. This enables improved penetration into tissue and imaging through optical opacities and is invisible to the subject. Topcon has recently developed an innovative OCTA algorithm, OCTARA (OCTA Ratio Analysis), which benefits from being paired with swept-source OCT. OCTARA aims to provide improved detection sensitivity of low blood flow and reduced motion artifacts without compromising axial resolution. In this chapter, we describe the implementation of OCTARA with swept-source OCT technology, the technical specifications of acquisition (e.g. the number of scans, area of examination field, etc.) along with the algorithm's function and principles for analysis of B-scan data to achieve angiographic visualization. Examples of OCTA scans performed using the OCTARA algorithm and a comparison of these scans with images obtained using other technologies are also presented.

New Directions in Ophthalmic Optical Coherence Tomography

The rapid development of optical coherence tomography (OCT) and its ophthalmic applications has resulted in the emergence of new laboratory and commercial systems that vary in performance and functionality. The introduction of high-speed imaging capabilities has abrogated the primary limitation of early OCT technology by providing in vivo three-dimensional volumetric reconstructions of both anterior and posterior segments of the human eye within reasonable time constraints. Currently, high-speed swept source OCT technology has made it possible to achieve OCT acquisition speeds of several million A-scans/s. Another direction of OCT development includes the introduction of adaptive optics to imaging of the posterior segment of the eye that allows correction of the eye's static and dynamic aberrations, resulting in the achievement of volumetric cellular resolution retinal imaging. In this review, we introduce readers to various aspects of the development of OCT technology within the context of its ophthalmic applications. We point out directions for future development and indicate different perspectives on this dynamically expanding method. We give a few examples of how OCT has been used over the past few years and describe how high-speed OCT imaging may be used in the future in clinical practice.