Corneal and Epithelial Thickness Mapping: Comparison of Swept-Source- and Spectral-Domain-Optical Coherence Tomography

Objective. To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Swept-Source-Optical Coherence Tomography with those of Spectral-Domain-OCT in normal eyes. Methods. 30 normal eyes of 30 patients were assessed by 3 trained operators with SS-OCT and SD-OCT. Results. The central and minimum ET obtained with both devices were correlated: central ET, r = 0.86, p < 0.05 ; minimum ET, r = 0.72, p < 0.05 . Compared with SD-OCT, SS-OCT tended to underestimate these figures by 1.4 and 1.9 μm on average. The central and minimum CT obtained with both devices were strongly correlated: central CT, r = 0.994, p < 0.05 ; minimum CT, r = 0.995, p < 0.05 . SS-OCT tended to overestimate these figures by 11 and 14 μm on average. Repeatability was good for both devices with a mean coefficient of variation of measurements <6% for ET and <2% for CT. Interoperator variability (standard deviation and COV) was significantly higher for SS-OCT than for SD-OCT for all local epithelial thicknesses and significantly lower for the central CT and several local corneal thicknesses, whereas no significant differences between both technologies were found for the central and minimum ET and the minimum CT. Conclusion. SS-OCT and SD-OCT provide reproducible measurements of CT and ET in normal corneas with a strong correlation between both technologies. However, both technologies are not interchangeable when the main thickness parameters (i.e., central and minimum CT and minimum ET) are used for diagnosing early keratoconus or calculating the expected residual stromal bed thickness before corneal refractive surgery or anterior lamellar keratoplasty.

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Comparison of Choroidal Thickness Measurements between Spectral-domain Optical Coherence Tomography and Swept-source Optical Coherence Tomography in Children

10.21203/rs.3.rs-149964/v1 ◽

2021 ◽

Author(s):

Chun On Lee ◽

Xiujuan Zhang ◽

Shumin Tang ◽

Li Jia Chen ◽

Carol Cheung ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Correlation Coefficient ◽

Choroidal Thickness ◽

Relative Difference ◽

Spectral Domain ◽

Optical Coherence ◽

Normal Children ◽

Swept Source ◽

Thickness Measurements ◽

Sd Oct

Abstract PURPOSE: Choroidal thickness is associated with many ocular conditions, interchangeability among different generations of optical coherence tomography is therefore important for both research purpose and clinical application. Hence, we compared choroidal thickness measurements between spectral-domain optical coherence tomography (SD-OCT) and swept-source optical coherence tomography (SS-OCT) in healthy pediatric eyes.METHODS: Children from the population–based Hong Kong Children Eye Study were recruited. Choroidal thickness was measured by both devices. Intra-class correlation coefficient (ICC) was used to compare the measurements.RESULTS: A total of 114 children with mean age of 7.38±0.82 years were included. The central foveal choroidal thickness (CFCT) measured by SD-OCT and SS-OCT was 273.24±54.29μm and 251.84±47.12μm respectively. Inter-device correlation coefficient was 0.840 (95%CI: 0.616-0.918). However, choroidal thickness obtained by SD-OCT was significantly thicker than that measured by SS-OCT with a mean difference of 21.40±33.13μm (P<0.001). Bland-Altman limit of agreement on the relative difference scale for SD-OCT/SS-OCT was 86.33μm. Validated conversion equation for translating SD-OCT CFCT measurement into SS-OCT was SS-OCT = 35.261 + 0.810 x SD-OCT. CONCLUSIONS: ICC shows an acceptable agreement between SD-OCT and SS-OCT, however, there was a significant inter-device difference of choroidal thickness measurements in normal children eyes. Therefore, the measurements are not interchangeable.

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Systematic ultrastructural comparison of swept-source and full-depth spectral domain optical coherence tomography imaging of diabetic macular oedema

British Journal of Ophthalmology ◽

10.1136/bjophthalmol-2019-314591 ◽

2019 ◽

Vol 104 (6) ◽

pp. 868-873 ◽

Cited By ~ 5

Author(s):

Christoph Mitsch ◽

Jan Lammer ◽

Sonja Karst ◽

Christoph Scholda ◽

Eleonore Pablik ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Layer Thickness ◽

Macular Oedema ◽

Diabetic Macular Oedema ◽

Spectral Domain ◽

Retinal Layer ◽

Systematic Bias ◽

Optical Coherence ◽

Swept Source ◽

Sd Oct

Background/AimsOptical coherence tomography (OCT) is commonly used to diagnose and assess diabetic macular oedema (DME). Swept-source OCT (SS-OCT) promises improved imaging depth and more independence from media opacities. Heidelberg Spectralis full-depth imaging (FDI) combines details at different depths to one representation. The aim of this study was to determine the comparability of the imaging methods concerning DME ultrastructure.MethodsTwo graders assessed the presence of typical DME phenomena in eyes with centre-involving DME on Topcon Atlantis SS-OCT and Heidelberg Spectralis FDI spectral-domain OCT (SD-OCT) B-scans. Retinal layer segmentation was corrected and choroidal layers were manually segmented. Graders measured cyst and subretinal fluid (SRF) diameters and counted hyper-reflective foci (HRF). Findings were recorded and statistically analysed.ResultsStatistically significant systematic biases (Spectralis-Atlantis) were found for the HRF count (outside the central mm, −6.39, p=0.0338), chorioretinal thickness (central mm: −35.45 µm, p=0.00034), choroidal thickness (central mm: −60.97 µm, p=0.00004) and Sattler’s layer thickness (−42.69 µm, p=0.0001). Intergrader agreement was excellent or very good for posterior vitreous detachment, vitreomacular attachment (central mm) and SRF presence in both devices. Manually delineated Sattler’s layer thickness showed an intraclass correlation of 0.85 with FDI SD-OCT but 0.26 with SS-OCT (p=0.003).ConclusionProminent aspects such as cysts in the outer nuclear layer and SRF can be identified with comparable confidence, while a significant systematic bias underlies chorioretinal, choroidal and Sattler’s layer thickness and HRF count. Specialists should use the same device at every examination during longitudinal clinical consideration or cross-sectional evaluation of these ultrastructural biomarkers.

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Comparison of Macular Thickness Measurements Using Swept-Source and Spectral-Domain Optical Coherence Tomography in Healthy and Diabetic Subjects

10.1101/2020.11.22.20236307 ◽

2020 ◽

Author(s):

Kun Xiong ◽

Wei Wang ◽

Xia Gong ◽

Wangting Li ◽

Yuting Li ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Diabetic Retinopathy ◽

Macular Thickness ◽

Spectral Domain ◽

Optical Coherence ◽

Swept Source ◽

Macular Volume ◽

Conversion Equation ◽

Thickness Measurements ◽

Sd Oct

AbstractPurposeTo compare macular thicknesses measured using swept-source optical coherence tomography (SS-OCT) and spectral domain OCT (SD-OCT) in normal subjects, diabetics with diabetic retinopathy (DR) and diabetics without DR (NDR).MethodsWe analysed 510 normal eyes, 741 NDR eyes and 209 DR eyes. Mean macular thicknesses in Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, central point thicknesses (CPT), and macular volume were measured by SS-OCT and SD-OCT. We assessed agreement between SS-OCT and SD-OCT measurements by intraclass correlation coefficients (ICC) and Bland-Altman plots, and established a conversion equation relating central subfield (CSF), CPT and macular volume between the two devices.ResultsMacular thickness measurements by SS-OCT were significantly thinner than those by SD-OCT. The mean CSF thickness in normal eyes measured by SD-OCT and SS-OCT were 226.6 ± 19.1 μm (male 236.1 ± 19.1 μm vs female 223.0 ± 17.9 μm, p < 0.0001) and 258.4 ± 19.8 μm. In all three groups, the agreement between SS-OCT and SD-OCT was excellent (all ICC ≥ 0.866). For CSF the conversion equation SD-OCT = 31.95 + 0.999 × SS-OCT was derived. Using the equation, with 99.6% and 97.6% of the predicted values for CSF fell within 10% of the actual measurements in DR and NDR eyes, respectively.ConclusionWe propose SS-OCT CSF thicknesses of 275 μm for males and 260 μm for females as the minimum criteria for macular edema in Chinese eyes. And SS-OCT measurements were significantly thinner than those of SD-OCT, we derived an equation to convert SS-OCT measurements to SD-OCT equivalents.

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Complete Removal of Arbitrarily Strong and Arbitrarily Located Auto Correlation Artifacts in Spectral Domain Optical Coherence Tomography: Demonstration of an Efficient and Cost Effective Technique

10.20944/preprints202001.0132.v1 ◽

2020 ◽

Author(s):

Hari Nandakumar ◽

SatyaPrasanna Mallick ◽

Shailesh Srivastava

Keyword(s):

Optical Coherence Tomography ◽

Cost Effective ◽

Complete Removal ◽

Spectral Domain ◽

Optical Coherence ◽

Effective Technique ◽

Spectral Domain Oct ◽

Auto Correlation ◽

Cost Effective Technique ◽

Sd Oct

The proof-of-principle demonstration of a simple, yet effective method of autocorrelation artifact removal for optical coherence tomography (OCT) is presented using a custom-designed parallel spectral-domain OCT (SD-OCT) instrument. Our real-time method is based on time-averaged sampling of a sinusoidal phase modulation in the reference arm. Unlike other existing methods, our technique can completely eliminate arbitrarily located, arbitrarily strong autocorrelation artifacts.

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Neural network-based image reconstruction in swept-source optical coherence tomography using undersampled spectral data

Light Science & Applications ◽

10.1038/s41377-021-00594-7 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Yijie Zhang ◽

Tairan Liu ◽

Manmohan Singh ◽

Ege Çetintaş ◽

Yilin Luo ◽

...

Keyword(s):

Neural Network ◽

Optical Coherence Tomography ◽

Deep Learning ◽

Image Reconstruction ◽

Spectral Data ◽

Spectral Domain ◽

Optical Coherence ◽

Swept Source ◽

Spatial Aliasing ◽

Spectral Domain Oct

AbstractOptical coherence tomography (OCT) is a widely used non-invasive biomedical imaging modality that can rapidly provide volumetric images of samples. Here, we present a deep learning-based image reconstruction framework that can generate swept-source OCT (SS-OCT) images using undersampled spectral data, without any spatial aliasing artifacts. This neural network-based image reconstruction does not require any hardware changes to the optical setup and can be easily integrated with existing swept-source or spectral-domain OCT systems to reduce the amount of raw spectral data to be acquired. To show the efficacy of this framework, we trained and blindly tested a deep neural network using mouse embryo samples imaged by an SS-OCT system. Using 2-fold undersampled spectral data (i.e., 640 spectral points per A-line), the trained neural network can blindly reconstruct 512 A-lines in 0.59 ms using multiple graphics-processing units (GPUs), removing spatial aliasing artifacts due to spectral undersampling, also presenting a very good match to the images of the same samples, reconstructed using the full spectral OCT data (i.e., 1280 spectral points per A-line). We also successfully demonstrate that this framework can be further extended to process 3× undersampled spectral data per A-line, with some performance degradation in the reconstructed image quality compared to 2× spectral undersampling. Furthermore, an A-line-optimized undersampling method is presented by jointly optimizing the spectral sampling locations and the corresponding image reconstruction network, which improved the overall imaging performance using less spectral data points per A-line compared to 2× or 3× spectral undersampling results. This deep learning-enabled image reconstruction approach can be broadly used in various forms of spectral-domain OCT systems, helping to increase their imaging speed without sacrificing image resolution and signal-to-noise ratio.

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Comparison of Macular Thickness Measurements Using Swept-Source and Spectral-Domain Optical Coherence Tomography in Healthy and Diabetic Subjects

Current Eye Research ◽

10.1080/02713683.2021.1908566 ◽

2021 ◽

pp. 1-7

Author(s):

Kun Xiong ◽

Xia Gong ◽

Wangting Li ◽

Li Yuting ◽

Jie Meng ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Macular Thickness ◽

Spectral Domain ◽

Optical Coherence ◽

Swept Source ◽

Thickness Measurements

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Comparison of swept-source versus spectral-domain optical coherence tomography angiography for detection of macular neovascularization

Graefe s Archive for Clinical and Experimental Ophthalmology ◽

10.1007/s00417-021-05229-6 ◽

2021 ◽

Author(s):

Anna Lentzsch ◽

Laura Schöllhorn ◽

Christel Schnorr ◽

Robert Siggel ◽

Sandra Liakopoulos

Keyword(s):

Optical Coherence Tomography ◽

Optical Coherence Tomography Angiography ◽

Spectral Domain ◽

Optical Coherence ◽

Cross Sectional ◽

Swept Source ◽

En Face ◽

Increased Sensitivity ◽

Sensitivity Specificity ◽

Subretinal Hyperreflective Material

Abstract Purpose To compare swept-source (SS) versus spectral-domain (SD) optical coherence tomography angiography (OCTA) for the detection of macular neovascularization (MNV). Methods In this prospective cohort study, 72 eyes of 54 patients with subretinal hyperreflective material (SHRM) and/or pigment epithelial detachment (PED) on OCT possibly corresponding to MNV in at least one eye were included. OCTA scans were acquired using two devices, the PLEX Elite 9000 SS-OCTA and the Spectralis SD-OCTA. Fluorescein angiography (FA) was used as reference. Two graders independently evaluated en face OCTA images using a preset slab as well as a manually modified slab, followed by a combination of en face and cross-sectional OCTA. Results Sensitivity (specificity) for the automated slabs was 51.7% (93.0%) for SS-OCTA versus 58.6% (95.3%) for SD-OCTA. Manual modification of segmentation increased sensitivity to 79.3% for SS-OCTA but not for SD-OCTA (58.6%). The combination of en face OCTA with cross-sectional OCTA reached highest sensitivity values (SS-OCTA: 82.8%, SD-OCTA: 86.2%), and lowest number of cases with discrepancies between SS-OCTA and SD-OCTA (4.2%). Fleiss kappa as measure of concordance between FA, SS-OCTA, and SD-OCTA was 0.56 for the automated slabs, 0.60 for the manual slabs, and 0.73 (good agreement) for the combination of en face OCTA with cross-sectional OCTA. Concordance to FA was moderate for the automated slabs and good for manual slabs and combination with cross-sectional OCTA of both devices. Conclusion Both devices reached comparable results regarding the detection of MNV on OCTA. Sensitivity for MNV detection and agreement between devices was best when evaluating a combination of en face and cross-sectional OCTA.

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Spectral-domain optical coherence tomography for evaluating palisades of Vogt in ocular surface disorders with limbal involvement

Scientific Reports ◽

10.1038/s41598-021-91999-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ying-Yi Chen ◽

Yi-Chen Sun ◽

Chia-Ying Tsai ◽

Hsiao-Sang Chu ◽

Jo-Hsuan Wu ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Ocular Surface ◽

Spectral Domain ◽

Optical Coherence ◽

Slit Lamp ◽

Ocular Rosacea ◽

Unilateral Disease ◽

Healthy Eyes ◽

Slit Lamp Biomicroscopy ◽

Sd Oct

AbstractSpectral-domain optical coherence tomography (SD-OCT) has been used to observe the morphology of the palisades of Vogt (POV) with satisfactory resolutions. In this study, we used SD-OCT to examine the microstructure of the POV in ocular surface disorders with limbal involvement. We detect subclinical limbal pathologies based on five parameters, including (1) decreased epithelial thickness, (2) loss of the sharp stromal tip, (3) loss of the smooth epithelial-stromal interface, (4) dilated stromal vessels, and (5) decreased POV density. Eighteen eyes of 10 patients with advancing wavelike epitheliopathy (AWE) and 15 eyes of 9 patients with phlyctenular keratitis/ocular rosacea were recruited. SD-OCT could detect abnormal changes in the POV in 100% of the lesion sites. In presumed-healthy areas of the diseased eyes diagnosed by slit-lamp biomicroscopy, SD-OCT detected abnormal changes in the POV in 100% of the eyes in both groups. In patients with unilateral disease, abnormal changes in the POV were detected by SD-OCT in 50% and 100% of presumed-healthy eyes diagnosed by slit-lamp biomicroscopy in the AWE group and phlyctenular keratitis/ocular rosacea group, respectively. SD-OCT is powerful in detecting POV changes in ocular surface disorders and can provide useful information that cannot be provided by slit-lamp biomicroscopy.

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Design and Implementation Guidelines for a Modular Spectral-Domain Optical Coherence Tomography Scanner

International Journal of Optics ◽

10.1155/2018/3726207 ◽

2018 ◽

Vol 2018 ◽

pp. 1-22 ◽

Cited By ~ 4

Author(s):

Farid Atry ◽

Israel Jacob De La Rosa ◽

Kevin R. Rarick ◽

Ramin Pashaie

Keyword(s):

Optical Coherence Tomography ◽

Imaging System ◽

Optical Design ◽

Spectral Domain ◽

Design Parameters ◽

Optical Coherence ◽

Custom Made ◽

Essential Knowledge ◽

Sd Oct

In the past decades, spectral-domain optical coherence tomography (SD-OCT) has transformed into a widely popular imaging technology which is used in many research and clinical applications. Despite such fast growth in the field, the technology has not been readily accessible to many research laboratories either due to the cost or inflexibility of the commercially available systems or due to the lack of essential knowledge in the field of optics to develop custom-made scanners that suit specific applications. This paper aims to provide a detailed discussion on the design and development process of a typical SD-OCT scanner. The effects of multiple design parameters, for the main optical and optomechanical components, on the overall performance of the imaging system are analyzed and discussions are provided to serve as a guideline for the development of a custom SD-OCT system. While this article can be generalized for different applications, we will demonstrate the design of a SD-OCT system and representative results for in vivo brain imaging. We explain procedures to measure the axial and transversal resolutions and field of view of the system and to understand the discrepancies between the experimental and theoretical values. The specific aim of this piece is to facilitate the process of constructing custom-made SD-OCT scanners for research groups with minimum understanding of concepts in optical design and medical imaging.

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External limiting membrane: retinal structural barrier in diabetic macular edema

International Journal of Retina and Vitreous ◽

10.1186/s40942-021-00284-x ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Sandeep Saxena ◽

Levent Akduman ◽

Carsten H. Meyer

Keyword(s):

Optical Coherence Tomography ◽

Macular Edema ◽

Diabetic Macular Edema ◽

Spectral Domain ◽

Optical Coherence ◽

Barrier Effect ◽

External Limiting Membrane ◽

Ellipsoid Zone ◽

Structural Barrier ◽

Sd Oct

AbstractAdvances in spectral-domain optical coherence tomography (SD-OCT) technology have enhanced the understanding of external limiting membrane (ELM) and ellipsoid zone (EZ) in diabetic macular edema. An increase in VEGF has been demonstrated to be associated with sequential ELM and EZ disruption on SD-OCT. An intact ELM is a prerequisite for an intact EZ in DME. Anti-VEGF therapy leads to restoration of barrier effect of ELM. The ELM restores first followed by EZ restoration.

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