Spectral-domain Optical Coherence Tomography System Research Articles

Algorithm and software for field distortion correction in a commercial SD-OCT for corneal curvature assessment.

Accurate assessment of corneal curvatures using frequency domain optical coherence tomography (OCT) with galvanometer scanners remains challenging due to the well-known scan field distortion. This paper presents an algorithm and software for correcting the distortion using only two simple measurements in which a readily available standard sphere is positioned in different depths in front of the OCT scanner. This offers a highly accessible and easily reproducible method for the field distortion correction (FDC). The correction was validated by measuring different spherical phantoms and conducting corneal curvature measurements of ex vivo porcine corneas using a commercial spectral-domain OCT system and a clinically approved swept-source OCT as a reference instrument. Thus, the error in radius measurements of spherical phantoms was reduced by >90% and astigmatism by >80% using FDC. In explanted porcine eyes, the error in astigmatism measurements with the Telesto was reduced by 75% for power and 70% for angle. The best fitting sphere radius was determined up to a deviation of 0.4% from the Anterion. This paper describes a correction algorithm for OCT immanent distortion that is applicable to any scanning OCT setup and enables precise corneal curvature measurements. The MATLAB software for the FDC is publicly available on GitHub.

Clinical Evaluation of a New Spectral-Domain Optical Coherence Tomography-Based Biometer.

The VEMoS-AXL system is a new optical biometer based on spectral domain optical coherence tomography (SD-OCT) that has been tested in terms of intrasession repeatability and compared with a swept-source optical coherence tomography biometer (SS-OCT), which is recognized as the gold standard for the performance of an agreement analysis. A biometric analysis was performed three consecutive times in 120 healthy eyes of 120 patients aged between 18 and 40 years with the SD-OCT system, and afterwards, a single measurement was obtained with the SS-OCT system. Within-subject standard deviations were 0.004 mm, 4.394 µm, and 0.017 mm for axial length (AL), central corneal thickness (CCT), and anterior chamber depth (ACD) measures obtained with the SD-OCT biometer, respectively. The agreement between devices was good for AL (limits of agreement, LoA: -0.04 to 0.03 mm) and CCT (LoA: -4.36 to 14.38 µm), whereas differences between devices were clinically relevant for ACD (LoA: 0.03 to 0.21 mm). In conclusion, the VEMoS-AXL system provides consistent measures of anatomical parameters, being most of them interchangeable with those provided by the SS-OCT-based gold standard.

Real-Time Cavitation Monitoring During Optical Coherence Tomography Guided Photo-Mediated Ultrasound Therapy of the Retina.

Photo-mediated ultrasound therapy (PUT) is a novel antivascular therapeutic modality based on cavitation-induced bioeffects. During PUT, synergistic combinations of laser pulses and ultrasound bursts are used to remove the targeted microvessels selectively and precisely without harming nearby tissue. In the current study, an integrated system combining PUT and spectral domain optical coherence tomography (SD-OCT) was developed, where the SD-OCT system was used to guide PUT by detecting cavitation in real time in the retina of the eye. We first examined the capability of SD-OCT in detecting cavitation on a vascular-mimicking phantom and compared the results with those from a passive cavitation detector. The performance of the integrated system in treatment of choroidal microvessels was then evaluated in rabbit eyes in vivo. During the in vivo PUT experiments, several biomarkers at the subretinal layer in the rabbit eye were identified on OCT images. The findings indicate that, by evaluating biomarkers of treatment effect, real-time SD-OCT monitoring could help to avoid micro-hemorrhage, which is a potential major side effect. Real-time OCT monitoring can thus improve the safety and efficiency of PUT in removing the retinal and choroidal microvasculature.

Short-term Changes in Epithelial and Optical Redistribution Induced by Different Orthokeratology Designs.

This study aimed to investigate corneal epithelial and topographic changes caused by two commercial myopia orthokeratology (ortho-k) designs. Twenty-six subjects fitted with vision shape treatment (VST) lenses and 30 subjects fitted with corneal reshaping therapy (CRT) lenses were reviewed 1 day, 1 week, and 1 month after lens initiation. A spectral-domain optical coherence tomography system was used to create epithelial maps that were in turn used to determine the average epithelial thickness of each zone and the diameter of treatment zone. By measuring the topographic tangential differential map, the treatment zone diameter and the power and width of the high convex zone (HCZ) were obtained. All epithelial thicknesses and topographic corneal variations recorded were analyzed. At the central zone, the epithelial thickness changes (△ET) decreased significantly after 1 day of ortho-k in two groups. At 2- to 9-mm peripheral zone, ortho-k increased △ET until 1 week in the VST group, whereas it kept increasing in the CRT group after 1 week. At 1 month, the central △ET is -9.51±2.38 mm in the VST group, which was comparable to -8.72±3.43 mm in the CRT group. The nasal HCZ power and the △ET of nasal and inferior nasal were significantly larger in the CRT group. A positive correlation was found between the HCZ power and △ET generated by VST-type lenses inferiorly and temporally. For the CRT group, a positive correlation was found between inferior HCZ power and △ET. At the early stage of ortho-k, epithelial thickness and topography change quickly and simultaneously. Epithelial changes were in line with corneal topography reshaping. Epithelial and optical remodelling were affected by different lens types.

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.

Self-denoising method for OCT images with single spectrogram-based deep learning.

The presence of noise in images reconstructed with optical coherence tomography (OCT) is a key issue which limits the further improvement of the image quality. In this Letter, for the first time, to the best of our knowledge, a self-denoising method for OCT images is presented with single spectrogram-based deep learning. Different noises in different images could be customized with an extremely low computation. The deep-learning model consists of two fully connected layers, two convolution layers, and one deconvolution layer, with the input being the raw interference spectrogram and the label being its reconstructed image using the Fourier transform. The denoising image could be calculated by subtracting the noise predicted by our model from the label image. The OCT images of the TiO2 phantom, the orange, and the zebrafish obtained with our spectral-domain OCT system are used as examples to demonstrate the capability of our method. The results demonstrate its effectiveness in reducing noises such as speckle patterns and horizontal and vertical stripes. Compared with the label image, the signal-to-noise ratio could be improved by 35.0 dB, and the image contrast could be improved by a factor of two. Compared with the results denoised by the average method, the mean peak signal-to-noise ratio is 26.2 dB.

Self super-resolution of optical coherence tomography images based on deep learning.

As a medical imaging modality, many researches have been devoted to improving the resolution of optical coherence tomography (OCT). We developed a deep-learning based OCT self super-resolution (OCT-SSR) pipeline to improve the axial resolution of OCT images based on the high-resolution and low-resolution spectral data collected by the OCT system. In this pipeline, the enhanced super-resolution asymmetric generative adversarial networks were built to improve the network outputs without increasing the complexity. The feasibility and effectiveness of the approach were demonstrated by experimental results on the images of the biological samples collected by the home-made spectral-domain OCT and swept-source OCT systems. More importantly, we found the sidelobes in the original images can be obviously suppressed while improving the resolution based on the OCT-SSR method, which can help to reduce pseudo-signal in OCT imaging when non-Gaussian spectra light source is used. We believe that the OCT-SSR method has broad prospects in breaking the limitation of the source bandwidth on the axial resolution of the OCT system.

Correcting spatial-spectral crosstalk and chromatic aberrations in broadband line-scan spectral-domain OCT images.

Digital correction of optical aberrations allows for high-resolution imaging across the full depth range in optical coherence tomography (OCT). Many digital aberration correction (DAC) methods have been proposed in the past to evaluate and correct monochromatic error in OCT images. However, other factors that deteriorate the image quality have not been fully investigated. Specifically, in a broadband line-scan spectral-domain OCT system (LS-SD-OCT), photons with different wavelengths scattered from the same transverse location and in the imaged object will be projected onto different spatial coordinates onto the 2D camera sensor, which in this work is defined as spatial-spectral crosstalk. In addition, chromatic aberrations in both axial and lateral directions are not negligible for broad spectral bandwidths. Here we present a novel approach to digital recovery of the spatial resolution in images acquired with a broadband LS-SD-OCT, which addresses these two main factors that limit the effectiveness of DAC for restoring diffraction-limited resolution in LS-SD-OCT images. In the proposed approach, spatial-spectral crosstalk and chromatic aberrations are suppressed by the registration of monochromatic sub-band tomograms that are digitally corrected for aberrations. The new method was validated by imaging a standard resolution target, a microspheres phantom, and different biological tissues. LS-SD-OCT technology combined with the proposed novel image reconstruction method could be a valuable research tool for various biomedical and clinical applications.

Development of an optical coherence tomographic surface profiling system with a wide scanning area based on telecentric F–θ imaging optics

This study was conducted to develop an in situ tomographic profiling system that can detect surface defects over a wide area by applying a telecentric F–θ scanning optical system, with an effective measurement width of 200 mm, to a spectral domain optical coherence tomography (SD-OCT) system. A telecentric F–θ scanning optical system with an effective scanning length of up to 210 mm was designed. A focal depth up to 32 mm without loss of resolution was predicted when the entrance pupil diameter (EPD) was set to 4.0 mm. The obtained three-dimensional tomographic images of tire treads and scientific calculators confirmed the possibility of surface profiling for areas with a width of up to 200 mm and depth over 7 mm. Combining a large-area telecentric lens with an SD-OCT system made it possible to perform deep 3D profiling simultaneously with a large-area surface inspection. The developed surface tomographic profiling system can adjust the size of the EPD to achieve a resolution of less than 50 µm. It can thus provide axial and lateral resolutions equivalent to those of a conventional OCT system as well as a wide effective measurement area.

Powell lens-based line-field spectral domain optical coherence tomography system for cellular resolution imaging of biological tissue.

A Powell lens is used in a line-field spectral domain OCT (PL-LF-SD-OCT) system to generate a line-shaped imaging beam with almost uniform distribution of the optical power in the line direction. This design overcomes the severe sensitivity loss (∼10 dB) observed along the line length direction (B-scan) in LF-OCT systems based on cylindrical lens line generators. The PL-LF-SD-OCT system offers almost isotropic spatial resolution (Δx and Δy ∼2 µm, Δz ∼1.8 µm) in free space and sensitivity of ∼87 dB for 2.5 mW imaging power at 2,000 fps imaging rate with only ∼1.6 dB sensitivity loss along the line length. Images acquired with the PL-LF-SD-OCT system allow for visualization of the cellular and sub-cellular structure of biological tissues.

A comparison of optophysiological biomarkers of photoreceptor stress and phototoxicity in BALB/cJ, B6 (Cg)-Tyrc-2J/J, and C57Bl/6J mouse strains.

Ophthalmic imaging instruments, including the confocal scanning laser ophthalmoscope and spectral-domain optical coherence tomography system, originally intended for revealing ocular microstructures in the human eye, have been deployed by vision researchers to evaluate the eyes of numerous small and large animal species for more than two decades. In this study, we have used these two instruments to obtain imaging data sequentially from the retinas of three prominent, widely used experimental mouse models to document changes induced by two contrasting vivarium lighting conditions. Mice studied include albino BALB/cJ and B6(Cg)-Tyrc-2J/J and pigmented C57Bl/6J. Mice were reared under dim light conditions until ~8 weeks of age where they underwent baseline imaging. Following, mice were returned to the dim vivarium or relocated to the top rack cage position in a standard vivarium. Mice were then followed for several months by ocular imaging to catalog the retinal dynamics as a function of long-term dim vs. elevated, standard vivarium lighting exposure levels. Upon exposure to elevated light levels, B6(Cg)-Tyrc-2J/J underwent similar changes as BALB/cJ in regard to photoreceptor outer segment shortening, photoreceptor layer proximal aspect hyperreflective changes, and the development of retinal infoldings and autofluorescent sub-retinal inflammatory monocyte infiltrate. Noteworthy, however, is that infoldings and infiltrate occurred at a slower rate of progression in B6(Cg)-Tyrc-2J/J vs. BALB/cJ. The photoreceptor outer nuclear layer thickness of BALB/cJ degenerated steadily following elevated light onset. In contrast, B6(Cg)-Tyrc-2J/J degeneration was unremarkable for many weeks before experiencing a noticeable change in the rate of degeneration that was concomitant with a plateau and decreasing trend in number of retinal infoldings and monocyte infiltrate. Pathological changes in C57Bl/6J mice were unremarkable for all imaging biomarkers assessed with exception to autofluorescent sub-retinal inflammatory monocyte infiltrate, which showed significant accumulation in dim vs. elevated light exposed mice following ~1 year of observation. These data were evaluated using Spearman's correlation and Predictive Power Score matrices to determine the best imaging optophysiological biomarkers for indicating vivarium light stress and light-induced photoreceptor degeneration. This study suggests that changes in proximal aspect hyperreflectivity, outer segment shortening, retinal infoldings and autofluorescent sub-retinal inflammatory monocyte infiltrate are excellent indicators of light stress and light-induced degeneration in albino B6(Cg)-Tyrc-2J/J and BALB/cJ mouse strains.

Intraoperative application of optical coherence tomography for lung tumor.

On-site instant determination of benign or malignant tumors for deciding the types of resection is crucial during pulmonary surgery. We designed a portable spectral-domain optical coherence tomography (SD-OCT) system to do real-time scanning intraoperatively for the distinction of fresh tumor specimens in the lung. A total of 12 ex vivo lung specimens from six patients were enrolled. Three patients were diagnosed with invasive adenocarcinoma (IA), while the others were benign. After OCT-imaged reconstruction, we compared the qualitative morphology of OCT and histology among malignant, benign, and normal tissues. In addition, through analysis of the quantitative data, a discrete difference in optical attenuation coefficients around the junctional surface was shown by our data processing. This study demonstrated a feasible OCT-assisted resection guide by a rapid on-site tumor diagnosis. The results indicate that future deep learning of OCT-captured image systems able to improve diagnostic and therapeutic efficiency is warranted.

Surgical microscope integrated MHz SS-OCT with live volumetric visualization.

Intraoperative optical coherence tomography is still not overly pervasive in routine ophthalmic surgery, despite evident clinical benefits. That is because today's spectral-domain optical coherence tomography systems lack flexibility, acquisition speed, and imaging depth. We present to the best of our knowledge the most flexible swept-source optical coherence tomography (SS-OCT) engine coupled to an ophthalmic surgical microscope that operates at MHz A-scan rates. We use a MEMS tunable VCSEL to implement application-specific imaging modes, enabling diagnostic and documentary capture scans, live B-scan visualizations, and real-time 4D-OCT renderings. The technical design and implementation of the SS-OCT engine, as well as the reconstruction and rendering platform, are presented. All imaging modes are evaluated in surgical mock maneuvers using ex vivo bovine and porcine eye models. The applicability and limitations of MHz SS-OCT as a visualization tool for ophthalmic surgery are discussed.

Insights into Sickle Cell Disease through the Retinal Microvasculature: Adaptive Optics Scanning Light Ophthalmoscopy Correlates of Clinical OCT Angiography.

Clinical OCT angiography (OCTA) of the retinal microvasculature offers a quantitative correlate to systemic disease burden and treatment efficacy in sickle cell disease (SCD). The purpose of this study was to use the higher resolution of adaptive optics scanning light ophthalmoscopy (AOSLO) to elucidate OCTA features of parafoveal microvascular compromise identified in SCD patients. Case series of 11 SCD patients and 1 unaffected control. A total of 11 eyes of 11 SCD patients (mean age, 33 years; range, 23-44; 8 female, 3 male) and 1 eye of a 34-year-old unaffected control. Ten sequential 3 × 3 mm parafoveal OCTA full vascular slab scans were obtained per eye using a commercial spectral domain OCT system (Avanti RTVue-XR; Optovue). These were used to identify areas of compromised perfusion near the foveal avascular zone (FAZ), designated as regions of interest (ROIs). Immediately thereafter, AOSLO imaging was performed on these ROIs to examine the cellular details of abnormal perfusion. Each participant was imaged at a single cross-sectional time point. Additionally, 2 of the SCD patients were imaged prospectively 2 months after initial imaging to study compromised capillary segments across time and with treatment. Detection and characterization of parafoveal perfusion abnormalities identified using OCTA and resolved using AOSLO imaging. We found evidence of abnormal blood flow on OCTA and AOSLO imaging among all 11 SCD patients with diverse systemic and ocular histories. Adaptive optics scanning light ophthalmoscopy imaging revealed a spectrum of phenomena, including capillaries with intermittent blood flow, blood cell stasis, and sites of thrombus formation. Adaptive optics scanning light ophthalmoscopy imaging was able to resolve single sickled red blood cells, rouleaux formations, and blood cell-vessel wall interactions. OCT angiography and AOSLO imaging were sensitive enough to document improved retinal perfusion in an SCD patient 2 months after initiation of oral hydroxyurea therapy. Adaptive optics scanning light ophthalmoscopy imaging was able to reveal the cellular details of perfusion abnormalities detected using clinical OCTA. The synergy between these clinical and laboratory imaging modalities presents a promising avenue in the management of SCD through the development of noninvasive ocular biomarkers to prognosticate progression and measure the response to systemic treatment.

Choroidal structural changes in airline pilots and cabin crew.

To analyze the differences in terms of choroidal vascularity index (CVI) and choroidal thickness (CT) between the airline pilots-cabin crew and the normal population. In this prospective study, 50 airline pilots-cabin crew (study group) and 50 healthy individuals (control group) were included for comparison. For each participant, one eye, the eye with the higher OCT scan score index, was enrolled. Subfoveal CT and CVI were measured using a spectral-domain optical coherence tomography system with enhanced depth imaging. There were no significant differences in terms of age and sex between the study and control groups. The mean CT was 368.5 ± 79.6 in the control group vs. 424.9 ± 80.7 in the study group (p = 0.001). CT was significantly thicker in the study group. The mean CVI was 64.3 ± 1.5 in the control group and 66 ± 3.1 in the study group (p = 0.5). There was no significant correlation between the study and control groups in terms of CVI. Airline pilots-cabin crew had thicker CT, but there were no differences in CVI when they were compared with healthy subjects. The effect of unique occupational exposures of airline pilots-cabin crew to the pathophysiology of choroidal structural alterations needs further investigation.

Abstract 11913: In vivo Optical Coherence Tomography Angiography of the Coronary Microcirculation

Introduction: Imaging the coronary microcirculation in the beating heart is challenging due to motion artifact from cardiac contraction and respiration, which limits the application of high-resolution microscopy techniques. In the brain and other tissues with less motion artifact, optical coherence tomography angiography (OCTA) has been successfully used in rodents to create label-free maps of blood flow down to the capillary level. We hypothesized that advanced cardiac and respiratory gating together with high-speed optical coherence tomography can be used to implement OCTA of the capillary microcirculation in vivo in the mouse heart. Methods: C57BL/6 mice (n=30) were imaged through a sternotomy while anesthetized and ventilated. OCTA was performed using a custom tissue stabilizer and a Thorlabs TEL 321 Spectral Domain OCT system, which was synchronized to physiologic signals using custom hardware and software and cardiac pacing protocols. The system had an optical center wavelength of 1300 nm and produced axial (depth) and lateral resolutions of 4.2 μm and 13 μm, respectively. Angiograms were created from the difference between two consecutive images acquired during diastole, and a volumetric three-dimensional scan was acquired over multiple cardiac cycles. Images were analyzed in MATLAB and ImageJ to produce projection angiograms of the coronary microcirculation. Results: OCTA with cardiac and respiratory gating can produce high-resolution angiograms of the coronary microcirculation without exogenous contrast agents. OCTA has improved imaging depth and field of view compared to conventional confocal microscopy, and can produce widefield coronary angiograms (Fig. 1A) while maintaining the ability to visualize individual capillaries (Fig. 1B). Conclusion: In vivo OCTA can image the coronary microcirculation in the heart and will provide a powerful new tool for investigating coronary microvascular dysfunction in mouse models of heart disease.

A novel approach for forensic identification of automotive paints using optical coherence tomography and multivariate statistical methods.

Automotive paint is one of the most important evidence in solving vehicle-related criminal cases. It contains the critical information about the suspected vehicle, providing essential clues for the investigation. In this study, a novel approach based on optical coherence tomography combined with multivariate statistical methods was proposed to facilitate rapid, accurate and nondestructive identification of different brands of automotive paints. 164 automotive paint samples from 8 different manufacturers were analyzed by a spectral-domain optical coherence tomography system (SD-OCT). Two-dimensional cross-sectional OCT images and three-dimensional OCT reconstruction of vehicle paints of different paints were obtained to show the internal structural differences. Visual discrimination of A-scan data after registration and averaging processing was first used to distinguish different samples. An scanning electron microscope was utilized to obtain the cross-sectional image of the sample to evaluate the effectiveness of OCT technique. Then the original A-scan data, first derivative data and second derivative data of 136 paints with four layers from 7 different manufacturers were collected. Multivariate statistical methods, including principal component analysis (PCA), multi-layer perceptron (MLP), k-nearest neighbor (KNN) algorithm and Bayes discriminant analysis (BDA), were used to analyze different datasets. The results show the hybrid PCA and BDA model based on the first derivative OCT data achieved the best result of 100% accuracy on the testing dataset for identifying automotive paints. It is demonstrated that the OCT technique combined with multivariate statistics could be a promising method for identifying the automotive paints rapidly and accurately.

A Diabetic Retinopathy Classification Framework Based on Deep-Learning Analysis of OCT Angiography.

PurposeReliable classification of referable and vision threatening diabetic retinopathy (DR) is essential for patients with diabetes to prevent blindness. Optical coherence tomography (OCT) and its angiography (OCTA) have several advantages over fundus photographs. We evaluated a deep-learning-aided DR classification framework using volumetric OCT and OCTA.MethodsFour hundred fifty-six OCT and OCTA volumes were scanned from eyes of 50 healthy participants and 305 patients with diabetes. Retina specialists labeled the eyes as non-referable (nrDR), referable (rDR), or vision threatening DR (vtDR). Each eye underwent a 3 × 3-mm scan using a commercial 70 kHz spectral-domain OCT system. We developed a DR classification framework and trained it using volumetric OCT and OCTA to classify eyes into rDR and vtDR. For the scans identified as rDR or vtDR, 3D class activation maps were generated to highlight the subregions which were considered important by the framework for DR classification.ResultsFor rDR classification, the framework achieved a 0.96 ± 0.01 area under the receiver operating characteristic curve (AUC) and 0.83 ± 0.04 quadratic-weighted kappa. For vtDR classification, the framework achieved a 0.92 ± 0.02 AUC and 0.73 ± 0.04 quadratic-weighted kappa. In addition, the multiple DR classification (non-rDR, rDR but non-vtDR, or vtDR) achieved a 0.83 ± 0.03 quadratic-weighted kappa.ConclusionsA deep learning framework only based on OCT and OCTA can provide specialist-level DR classification using only a single imaging modality.Translational RelevanceThe proposed framework can be used to develop clinically valuable automated DR diagnosis system because of the specialist-level performance showed in this study.

Optical coherence tomography for surgical margin evaluation of excised canine cutaneous and subcutaneous tumours.

Currently, intraoperative tumour margin imaging is not routinely utilized in veterinary medicine. Optical coherence tomography (OCT) allows for real-time assessment of tissue morphology of 1-2 mm depth. The aims of this study were (1) to compare the histologic and OCT features of excised canine skin and subcutaneous specimens, and (2) to determine the diagnostic accuracy of OCT for surgical margin evaluation. The authors hypothesized that OCT imaging would correlate well with histopathology and that OCT would be sensitive for detection of incomplete margins. Eighty dogs were prospectively enrolled. Tumours were excised, and the surgical margins were imaged using a spectral domain OCT system. The tumour type and completeness of excision were determined by histopathology. Nine blinded observers received training in OCT image interpretation and were then given a set of OCT images and videos. The observers assigned each image/video a grade from 1 (no tumour) to 4 (tumour) and the results were compared to histopathology. The overall median sensitivity and specificity of OCT imaging for detection of incomplete margins were 86.7% and 84.6%, respectively. A potential limitation is that observers had varied experience with OCT image interpretation, ranging from no prior experience to participating in a previous OCT project. OCT is sensitive for detection of incomplete margins and could be a promising real-time surgical margin imaging modality. Further study is needed to evaluate intraoperative applications of OCT and its impact on tumour recurrence and long-term outcome.

Line-scanning SD-OCT for in-vivo, non-contact, volumetric, cellular resolution imaging of the human cornea and limbus.

In-vivo, non-contact, volumetric imaging of the cellular and sub-cellular structure of the human cornea and limbus with optical coherence tomography (OCT) is challenging due to involuntary eye motion that introduces both motion artifacts and blur in the OCT images. Here we present the design of a line-scanning (LS) spectral-domain (SD) optical coherence tomography system that combines 2 × 3 × 1.7 µm (x, y, z) resolution in biological tissue with an image acquisition rate of ∼2,500 fps, and demonstrate its ability to image in-vivo and without contact with the tissue surface, the cellular structure of the human anterior segment tissues. Volumetric LS-SD-OCT images acquired over a field-of-view (FOV) of 0.7 mm × 1.4 mm reveal fine morphological details in the healthy human cornea, such as epithelial and endothelial cells, sub-basal nerves, as well as the cellular structure of the limbal crypts, the palisades of Vogt (POVs) and the blood microvasculature of the human limbus. LS-SD-OCT is a promising technology that can assist ophthalmologists with the early diagnostics and optimal treatment planning of ocular diseases affecting the human anterior eye.