Advances In Optical Coherence Tomography Research Articles

Novel OCT prognostic indicators in diabetic macular oedema

PurposeDespite advances in optical coherence tomography (OCT), clinicians have few prognostic indicators. We chose anomalous features found in OCTs, and retrospectively analysed OCT images for subsequent progression in visual acuity (VA), OCT results and interventions required over 22–24 months.MethodsPutative risk factors were grouped into sets based on similar putative aetiology: sub‐retinal fluid and large cysts, hyperreflective dots, partial/total disorganisation of retinal inner layers (DRIL) and photoreceptor disruption, epiretinal membranes, vitreomacular traction, vitreomacular adhesion. Eyes were stratified according to how many of these groups of features they displayed (0–4) and were all treated as per protocol and clinical need.ResultsIncreasing risk factors correlated with increasing initial OCT central retinal thickness (CRT) (387 vs. 555) and volume (9.99 vs. 11.28), and poorer initial visual acuity (0.41 vs. 0.60) on presentation.Whilst final CRT results showed no significant differences between the groups (325–248 nm), and no significant differences between numbers of injections performed (6.8 vs. 7.35), more features correlated with poorer VA, both absolute and relative to baseline, irrespective of whether there had been previous treatment.ConclusionsThese features are better prognostic indicators than OCT measurements alone.

The fundus photo has met its match: optical coherence tomography and adaptive optics ophthalmoscopy are here to stay.

Over the past 25years, optical coherence tomography (OCT) and adaptive optics (AO) ophthalmoscopy have revolutionised our ability to non-invasively observe the living retina. The purpose of this review is to highlight the techniques and human clinical applications of recent advances in OCT and adaptive optics scanning laser/light ophthalmoscopy (AOSLO) ophthalmic imaging. Optical coherence tomography retinal and optic nerve head (ONH) imaging technology allows high resolution in the axial direction resulting in cross-sectional visualisation of retinal and ONH lamination. Complementary AO ophthalmoscopy gives high resolution in the transverse direction resulting in en face visualisation of retinal cell mosaics. Innovative detection schemes applied to OCT and AOSLO technologies (such as spectral domain OCT, OCT angiography, confocal and non-confocal AOSLO, fluorescence, and AO-OCT) have enabled high contrast between retinal and ONH structures in three dimensions and have allowed invivo retinal imaging to approach that of histological quality. In addition, both OCT and AOSLO have shown the capability to detect retinal reflectance changes in response to visual stimuli, paving the way for future studies to investigate objective biomarkers of visual function at the cellular level. Increasingly, these imaging techniques are being applied to clinical studies of the normal and diseased visual system. Optical coherence tomography and AOSLO technologies are capable of elucidating the structure and function of the retina and ONH noninvasively with unprecedented resolution and contrast. The techniques have proven their worth in both basic science and clinical applications and each will continue to be utilised in future studies for many years to come.

Scalable wide-field optical coherence tomography-based angiography for in vivo imaging applications.

Recent advances in optical coherence tomography (OCT)-based angiography have demonstrated a variety of biomedical applications in the diagnosis and therapeutic monitoring of diseases with vascular involvement. While promising, its imaging field of view (FOV) is however still limited (typically less than 9 mm2), which somehow slows down its clinical acceptance. In this paper, we report a high-speed spectral-domain OCT operating at 1310 nm to enable wide FOV up to 750 mm2. Using optical microangiography (OMAG) algorithm, we are able to map vascular networks within living biological tissues. Thanks to 2,048 pixel-array line scan InGaAs camera operating at 147 kHz scan rate, the system delivers a ranging depth of ~7.5 mm and provides wide-field OCT-based angiography at a single data acquisition. We implement two imaging modes (i.e., wide-field mode and high-resolution mode) in the OCT system, which gives highly scalable FOV with flexible lateral resolution. We demonstrate scalable wide-field vascular imaging for multiple finger nail beds in human and whole brain in mice with skull left intact at a single 3D scan, promising new opportunities for wide-field OCT-based angiography for many clinical applications.

Advances of optical coherence tomography in myopia and pathologic myopia.

The natural course of high-axial myopia is variable and the development of pathologic myopia is not fully understood. Advancements in optical coherence tomography (OCT) technology have revealed peculiar intraocular structures in highly myopic eyes and unprecedented pathologies that cause visual impairment. New OCT findings include posterior precortical vitreous pocket and precursor stages of posterior vitreous detachment; peripapillary intrachoroidal cavitation; morphological patterns of scleral inner curvature and dome-shaped macula. Swept source OCT is capable of imaging deeper layers in the posterior pole for investigation of optic nerve pits, stretched and thinned lamina cribrosa, elongated dural attachment at posterior scleral canal, and enlargement of retrobulbar subarachnoid spaces. This has therefore enabled further evaluation of various visual field defects in high myopia and the pathogenesis of glaucomatous optic neuropathy. OCT has many potential clinical uses in managing visual impairing conditions in pathologic myopia. Understanding how retinal nerve fibers are redistributed in axial elongation will allow the development of auto-segmentation software for diagnosis and monitoring progression of glaucoma. OCT is indispensable in the diagnosis of various conditions associated with myopic traction maculopathy and monitoring of post-surgical outcomes. In addition, OCT is commonly used in the multimodal imaging assessment of myopic choroidal neovascularization. Biometry and topography of the retinal layers and choroid will soon be validated for the classification of myopic maculopathy for utilization in epidemiological studies as well as clinical trials.

Current concepts in pseudotumor cerebri.

Idiopathic intracranial hypertension (IIH) is a potentially blinding disorder of unknown cause, characterized by elevated intracranial pressure in the absence of a mass lesion, venous sinus thrombosis, or meningitis. This review summarizes recent developments and insights from leading treatment trials, emerging treatment options, and evolving ways to evaluate IIH. The Idiopathic Intracranial Hypertension Treatment Trial is the first large-scale, randomized, prospective study to evaluate medical treatment of patients with mild vision loss. These data have facilitated our understanding of baseline clinical manifestations, including impact on quality of life and treatment outcomes. Recent hypotheses and studies evaluating the role of cerebral venous sinus stenosis and stenting are discussed. Technological advances in optical coherence tomography are emerging to provide novel ways of evaluating and tracking optic disc swelling in IIH. Recent changes in defining IIH, understanding the impact and treatment of mild visual loss, and the roles that cerebral venous stenting and optical coherence tomography might have in clinical practice provide the framework to better treat patients with IIH.

Advances of optical coherence tomography in the in vivo study of lamina cribrosa

The lamina cribrosa is a sieve-like connective tissue beams located in the optic disc and the end of sclera, providing structural and nutritional support to the retinal ganglion cell axons as they traverse the optic disc. Substantial evidence suggests that the initial site of axonal injury likely occurs at the level of the lamina cribrosa. With the advances of optical coherence tomography (OCT) technologies, such as enhanced depth imaging, swept-source OCT enables us to unveil the lamina cribrosa in vivo features, including lamina cribrosa depth, lamina cribrosa thickness, and the change of lamina cribrosa microarchitecture. The imaging information obtained from these OCT technologies could be used to evaluate the damage of glaucoma, providing effective means for early diagnosis, assessment and prognosis of glaucoma. The studies of lamina cribrosa were reviewed using advanced OCT technologies. Key words: Tomography, optical coherence; Glaucoma; Lamina cribrosa

Advances in Optical Coherence Tomography in Clinical and Surgical Management of Vitreomacular Disease.

Advances in Optical Coherence Tomography in Clinical and Surgical Management of Vitreomacular Disease.

Investigating the choriocapillaris and choroidal vasculature with new optical coherence tomography technologies.

The body of knowledge of invivo investigation of the choroid has been markedly enhanced by recent technological advances in optical coherence tomography (OCT). New insights elucidating the morphological features of the choriocapillaris and choroidal vasculature, in both physiological and pathological conditions, indicate that the choroid plays a pivotal role in many posterior segment diseases. In this article, a review of the histological characteristics of the choroid, which must be considered for the proper interpretation of invivo imaging, is followed by a comprehensive discussion of fundamental principles of the current state-of-the-art in OCT, including cross-sectional OCT, en face OCT, and OCT angiography using both spectral domain OCT and swept source OCT technologies. A detailed review of the tomographic features of the choroid in the normal eye is followed by relevant findings in prevalent chorioretinal diseases, focusing on major causes of vision loss such as typical early and advanced age-related macular degeneration, polypoidal choroidal vasculopathy, central serous chorioretinopathy, pachychoroid spectrum disorders, diabetic choroidopathy, and myopia.

Choroidal thickness in acute and convalescent VKH disease

SummaryVogt‐Koyanagi‐Harada (VKH) disease is a systemic autoimmune disorder against melanocytes, and is one of the leading causes of uveitis in many countries including Japan. The distribution of the melanocytes in the systemic organ such as eyes, internal ears, meninges, or skin, leads to the various symptoms or signs of VKH disease. Because melanocytes are abundantly present in the choroid, the primary site of the intraocular inflammation of VKH disease is the choroid. Therefore, to monitor the disease activity of VKH disease, indocyanine green angiography (ICGA) had long been the most useful tool. Recently, advances in optical coherence tomography (OCT) made it possible to visualize the cross section of the choroid in addition to the retina, and the findings in choroidal OCT are found to complement those in ICGA. In this presentation, the features of the choroidal changes by ICGA and OCT in VKH disease are discussed.

A paradigm shift in imaging biomarkers in neovascular age-related macular degeneration

Neovascular age-related macular degeneration (AMD) has undergone substantial break-throughs in diagnostic as well as therapeutic respect, with optical coherence tomography (OCT) allowing to identify disease morphology in great detail, and intravitreal anti-vascular endothelial growth factor therapy providing unprecedented benefit. However, these two paths have yet not been combined in an optimal way, real-world outcomes are inferior to expectations, and disease management is largely inefficient in the real-world setting. This dilemma can be solved by identification of valid biomarkers relevant for visual function, disease activity and prognosis, which can provide solid guidance for therapeutic management on an individual level as well as on the population base. Qualitative and quantitative morphological features obtained by advanced OCT provide novel insight into exudative and degenerative stages of neovascular AMD. However, conclusions from structure/function correlations evolve differently from previous paradigms. While central retinal thickness was used as biomarker for guiding retreatment management in clinical trials and practice, fluid localization in different compartments offers superior prognostic value: Intraretinal cystoid fluid has a negative impact on visual acuity and is considered as degenerative when persisting through the initial therapeutic interval. Subretinal fluid is associated with superior visual benefit and a lower rate of progression towards geographic atrophy. Detachment of the retinal pigment epithelium was identified as most pathognomonic biomarker, often irresponsive to therapy and responsible for visual decline during a pro-re-nata regimen. Alterations of neurosensory tissue are usually associated with irreversible loss of functional elements and a negative prognosis. Novel OCT technologies offer crucial insight into corresponding changes at the level of the photoreceptor--retinal pigment epithelial--choriocapillary unit, identifying the biological limits of therapeutic interventions. To optimally benefit from high-resolution multi-modal imaging, an integrated analysis of all functional and structural features is required involving reliable automated algorithms and computational data analyses. Using innovative analysis methods, retinal biomarkers can be used to provide efficient personalized therapy for the individual patient, predictive disease- and population-based models for large-scale management and identifying promising targets for the development of novel therapeutic strategies.

Lamina Cribrosa in Glaucoma: Diagnosis and Monitoring.

The lamina cribrosa is the putative site of retinal ganglion cell axonal injury in glaucoma. Although histological studies have provided evidence of structural changes to the lamina cribrosa, even in early stages of glaucoma, until recently, the ability to evaluate the lamina cribrosa in vivo has been limited. Recent advances in optical coherence tomography, including enhanced depth and swept-source imaging, have changed this, providing a means to image the lamina cribrosa. Imaging has identified general and localized configurational changes in the lamina of glaucomatous eyes, including posterior laminar displacement, altered laminar thickness, and focal laminar defects with spatial association with conventional structural and functional losses. In addition, although the temporal relationship between changes to the lamina cribrosa and glaucomatous retinal ganglion cell loss is yet to be elucidated, quantitative measurements of laminar microarchitecture have good reproducibility and offer the potential to serve as biomarkers for glaucoma diagnosis and progression.

Myopic foveoschisis: a clinical review.

To review the literature on epidemiology, clinical features, diagnostic imaging, natural history, management, therapeutic approaches, and prognosis of myopic foveoschisis. A systematic Pubmed search was conducted using search terms: myopia, myopic, staphyloma, foveoschisis, and myopic foveoschisis. The evidence base for each section was organised and reviewed. Where possible an authors' interpretation or conclusion is provided for each section. The term myopic foveoschisis was first coined in 1999. It is associated with posterior staphyloma in high myopia, and is often asymptomatic initially but progresses slowly, leading to loss of central vision from foveal detachment or macular hole formation. Optical coherence tomography is used to diagnose the splitting of the neural retina into a thicker inner layer and a thinner outer layer, but compound variants of the splits have been identified. Vitrectomy with an internal limiting membrane peel and gas tamponade is the preferred approach for eyes with vision decline. There has been a surge of new information on myopic foveoschisis. Advances in optical coherence tomography will continually improve our understanding of the pathogenesis of retinal splitting, and the mechanisms that lead to macular damage and visual loss. Currently, there is a good level of consensus that surgical intervention should be considered when there is progressive visual decline from myopic foveoschisis.

OCT Assessment of the Long-Term Vascular Healing Response 5 Years After Everolimus-Eluting Bioresorbable Vascular Scaffold

Although recent observations suggest a favorable initial healing process of the everolimus-eluting bioresorbable vascular scaffold (BVS), little is known regarding long-term healing response. This study assessed the in vivo vascular healing response using optical coherence tomography (OCT) 5 years after elective first-in-man BVS implantation. Of the 14 living patients enrolled in the Thoraxcenter Rotterdam cohort of the ABSORB A study, 8 patients underwent invasive follow-up, including OCT, 5 years after implantation. Advanced OCT image analysis included luminal morphometry, assessment of the adluminal signal-rich layer separating the lumen from other plaque components, visual and quantitative tissue characterization, and assessment of side-branch ostia "jailed" at baseline. In all patients, BVS struts were integrated in the vessel and were not discernible. Both minimum and mean luminal area increased from 2 to 5 years, whereas lumen eccentricity decreased over time. In most patients, plaques were covered by a signal-rich, low-attenuating layer. Minimum cap thickness over necrotic core was 155 ± 90 μm. One patient showed plaque progression and discontinuity of this layer. Side-branch ostia were preserved with tissue bridge thinning that had developed in the place of side-branch struts, creating a neo-carina. At long-term BVS follow-up, we observed a favorable tissue response, with late luminal enlargement, side-branch patency, and development of a signal-rich, low-attenuating tissue layer that covered thrombogenic plaque components. The small size of the study and the observation of a different tissue response in 1 patient warrant judicious interpretation of our results and confirmation in larger studies.

Recent advances in OCT imaging of the lamina cribrosa

The lamina cribrosa (LC) is believed to be the site of injury to retinal ganglion cell axons in glaucoma. The ability to visualise this structure has the potential to help...

Maximum likelihood Doppler frequency estimation under decorrelation noise for quantifying flow in optical coherence tomography.

Recent hardware advances in optical coherence tomography (OCT) have led to ever higher A-scan rates. However, the estimation of blood flow axial velocities is limited by the presence and type of noise. Higher acquisition rates alone do not necessarily enable precise quantification of Doppler velocities, particularly if the estimator is suboptimal. In previous work, we have shown that the Kasai autocorrelation estimator is statistically suboptimal under conditions of additive white Gaussian noise. In addition, for practical OCT measurements of flow, decorrelation noise affects Doppler frequency estimation by broadening the signal spectrum. Here, we derive a general maximum likelihood estimator (MLE) for Doppler frequency estimation that takes into account additive white noise as well as signal decorrelation. We compare the decorrelation MLE with existing techniques using simulated and flow phantom data and find that it has better performance, achieving the Cramer-Rao lower bound. By making an approximation, we also provide an interpretation of this method in the Fourier domain. We anticipate that this estimator will be particularly suited for estimating blood flow in in vivo scenarios.

Development in anterior segment imaging for glaucoma

Recent developments in anterior segment imaging enable high-resolution imaging with higher speeds than previous systems. This review will focus on advances in optical coherence tomography (OCT) imaging of the anterior segment with an emphasis on angle evaluation. Anterior segment imaging with OCT is possible with both time domain and Fourier domain devices, and with light sources of different wavelengths. Recent studies have identified new risk factors for angle closure and prediction models incorporating quantitative angle width parameters have been developed for detection of gonioscopically defined angle closure. Swept source OCT is a variation of Fourier domain OCT that allows three-dimensional imaging of the angle analogous to gonioscopy and novel quantitative parameters have been described for angle measurement with this technology. Fourier domain OCT devices have higher resolution and sampling density than time domain OCT and enable visualization of more angle structures such as the Schwalbe's line and Schlemm's canal. OCT technology is expanding our understanding of angle closure disease. Although it does not replace gonioscopy in angle evaluation, it may help us identify predictors of progression along the angle closure disease spectrum such that treatment may be better targeted.

SEGMENTATION AND CORRELATION OF OPTICAL COHERENCE TOMOGRAPHY AND X-RAY IMAGES FOR BREAST CANCER DIAGNOSTICS

Pre-operative X-ray mammography and intraoperative X-ray specimen radiography are routinely used to identify breast cancer pathology. Recent advances in optical coherence tomography (OCT) have enabled its use for the intraoperative assessment of surgical margins during breast cancer surgery. While each modality offers distinct contrast of normal and pathological features, there is an essential need to correlate image-based features between the two modalities to take advantage of the diagnostic capabilities of each technique. We compare OCT to X-ray images of resected human breast tissue and correlate different tissue features between modalities for future use in real-time intraoperative OCT imaging. X-ray imaging (specimen radiography) is currently used during surgical breast cancer procedures to verify tumor margins, but cannot image tissue in situ. OCT has the potential to solve this problem by providing intraoperative imaging of the resected specimen as well as the in situ tumor cavity. OCT and micro-CT (X-ray) images are automatically segmented using different computational approaches, and quantitatively compared to determine the ability of these algorithms to automatically differentiate regions of adipose tissue from tumor. Furthermore, two-dimensional (2D) and three-dimensional (3D) results are compared. These correlations, combined with real-time intraoperative OCT, have the potential to identify possible regions of tumor within breast tissue which correlate to tumor regions identified previously on X-ray imaging (mammography or specimen radiography).

Optical coherence tomography and fundus autofluorescence imaging in uveitis

The current role of optical coherence tomography (OCT) and fundus autofluorescence (FAF) imaging in the diagnosis and management of uveitis is summarized in this article. OCT can be useful to detect and monitor cystoid macular edema and epiretinal membrane, two findings that are very common in intermediate, posterior and pan-uveitis. Both OCT and FAF demonstrate unique findings in several forms of posterior uveitis including birdshot chorioretinopathy, multiple evanescent white dot syndrome, acute posterior multifocal placoid pigment epitheliopathy, acute zonal occult outer retinopathy, multifocal choroiditis and Vogt–Koyanagi–Harada disease. Advances in OCT have allowed detection of alterations in retinal microstructure (spectral-domain OCT) as well as variations in choroidal thickness (enhanced-depth imaging OCT). With new advances in imaging, OCT and FAF have been shown to be helpful in understanding the pathophysiology of and differentiating between various forms of uveitis. Both imaging techniques may be helpful in monitoring patients with uveitis over time.

Optical coherence tomography

Using optical coherence tomography (OCT) to image the larynx during diagnosis and treatment of a vast array of laryngeal disorders continues to develop along with innovative surgical techniques. Precise delineation of vocal fold-layered microstructure allows for better understanding of the impact of benign and malignant lesions on laryngeal function, and optical coherence is uniquely suited to provide detail of the interface between these lesions and adjacent normal tissue. This review provides the reader with a timely update on current clinical and research applications of OCT. Recent advances in OCT include adaptation of these modalities to obtain images of moving vocal folds and provide real-time information during procedures. Additionally, an augmented form of OCT called polarization-sensitive optical coherence tomography (PS-OCT) shows promise in further characterizing benign and malignant lesions and in delineating areas of normal pliability from scar. PS-OCT can quantify areas of increased collagen (scar) and three-dimensional PS-OCT imaging can visualize the extent and location of lesions within vocal folds. Imaging the layered microstructure of vocal folds to precisely delineate boundaries between normal pliability and scar provides valuable information during diagnosis and treatment of benign and malignant disorders. Current OCT imaging techniques are guiding phonomicrosurgical interventions and improving patient care.

Extracting cardiac shapes and motion of the chick embryo heart outflow tract from four-dimensional optical coherence tomography images

Recent advances in optical coherence tomography (OCT), and the development of image reconstruction algorithms, enabled four-dimensional (4-D) (three-dimensional imaging over time) imaging of the embryonic heart. To further analyze and quantify the dynamics of cardiac beating, segmentation procedures that can extract the shape of the heart and its motion are needed. Most previous studies analyzed cardiac image sequences using manually extracted shapes and measurements. However, this is time consuming and subject to inter-operator variability. Automated or semi-automated analyses of 4-D cardiac OCT images, although very desirable, are also extremely challenging. This work proposes a robust algorithm to semi automatically detect and track cardiac tissue layers from 4-D OCT images of early (tubular) embryonic hearts. Our algorithm uses a two-dimensional (2-D) deformable double-line model (DLM) to detect target cardiac tissues. The detection algorithm uses a maximum-likelihood estimator and was successfully applied to 4-D in vivo OCT images of the heart outflow tract of day three chicken embryos. The extracted shapes captured the dynamics of the chick embryonic heart outflow tract wall, enabling further analysis of cardiac motion.