Optical coherence tomography ophthalmoscopy

Background: The diagnosis of idiopathic central serous retinopathy (CSR) is usually based on biomicroscopy and fluorescein angiography (FA). The optical coherence tomography (OCT) ophthalmoscope produces en face OCT scans (OCT...

To evaluate how information from combined coronal optical coherence tomography (OCT) and confocal laser scanning ophthalmoscopy (SLO) with integrated simultaneous indocyanine green (ICG) dye angiography can be used in the diagnosis of a variety of macular diseases. A compact chin-rest-based OCT/confocal imaging system was used to produce the OCT image and excite the fluorescence in the ICG dye. The same eye fundus area can be visualized with coronal (C-scans, en face) OCT and ICG angiography simultaneously. Fast T scanning (transverse scanning, en face) was used to build B- or C-scan OCT images along with confocal SLO views, with and without ICG filtration. The OCT, confocal SLO and ICG fluorescence images were simultaneously presented in a three-screen format. A live mixing channel overlaid the ICG sequence on the coronal OCT slices in a fourth panel for immediate comparison. Thirty eyes were imaged. The pathologic conditions studied included classic and occult neovascular membranes, vascularized RPE detachments, polypoidal choroidal vasculopathy, traumatic choroidal rupture, diabetic maculopathy, central serous retinopathy, and macular drusen. Images were evaluated with special attention toward identifying novel relationships between morphology and function revealed by the superimposition of the studies. Simultaneous visualization of an en face (coronal, C-scan) OCT image and of an ICG angiogram, displayed side by side and superimposed, permits more precise correlations between late fluorescence accumulation with structures deep to the retinal surface at the retina-choroid interface. The multiplanar scanning also permits immediate B-scan OCT cross-sectional views of regions of abnormal fluorescence. The paper demonstrates the synergy between the two types of studies, functional and anatomic, in providing a more complete view of the pathologic condition.

To present the possibilities of a new system that combines optical coherence tomography (OCT) and confocal ophthalmoscopy, producing en face OCT images in patients with retinal diseases. A prototype OCT Ophthalmoscope (OTI, Toronto, Canada) was used to scan patients with retinal conditions. The system uses a super luminescent diode (lambda = 820 nm; Deltalambda = 20 nm) and currently scans at a rate of 2 frames per second. In each frame, the OCT Ophthalmoscope simultaneously produces a transversal OCT scan and a confocal image in the X/Y plane. Both images correspond pixel to pixel. Between January 2002 and August 2003, >800 patients with various retinal diseases were scanned with the OCT Ophthalmoscope. Illustrative cases with regularly seen macular diseases are presented, such as macular hole and central serous retinopathy. Current difficulties as well as future possibilities of this new en face OCT ophthalmoscope are discussed. By presenting normal and pathologic transversal OCT images made by a prototype OCT Ophthalmoscope, we show that it can provide information not available using conventional OCT imaging.

Previous studies have demonstrated that optical coherence tomography (OCT) could be used to delineate alterations in the microstructure of cartilage, and have suggested that changes in the polarization state of light as detected by OCT could provide information on the birefringence properties of articular cartilage as influenced by disease. In this study we have used both OCT and polarization sensitive optical coherence tomography (PS-OCT) technologies to evaluate normal and abnormal bovine articular cartilage according to established structural, organizational, and birefringent characteristics of degenerative joint disease (DJD) in order to determine if this technology can be used to differentiate various stages of DJD as a minimally invasive imaging tool. Fresh bovine femoral-tibial joints were obtained from an abattoir, and 45 cartilage specimens were harvested from 8 tibial plateaus. Whole ex vivo specimens of normal and degenerative articular cartilage were imaged by both OCT and PS-OCT, then fixed and processed for histological evaluation. OCT/PS-OCT images and corresponding histology sections of each specimen were scored according to a modified Mankin structural grading scale and compared. OCT and PS-OCT imaging allowed structural evaluation of intact articular cartilage along a 6 mm surface length to a depth of 2 mm with a transverse resolution of 12 microm and an axial resolution of 10 microm. The OCT and PS-OCT images demonstrated characteristic alterations in the structure of articular cartilage with a high correlation to histological evaluation (kappa = 0.776). The OCT images were able to demonstrate early to advanced structural changes of articular cartilage while the optical phase retardation images obtained by PS-OCT imaging were able to discriminate areas where disorganization of the cartilage matrix was present, however, these characteristics are much different than those reported where OCT images alone were used to characterize tissue birefringence. No evidence of differences in OCT or PS-OCT images were detected between specimens of similar structural characteristics where proteoglycan was judged present or absent by safranin-O Fast Green staining. The combined use of OCT and PS-OCT technologies to obtain images from a single system is able to demonstrate and discriminate between characteristics of very early stages of surface irregularities not previously reported for OCT imaging, to deep clefts and collagen matrix disorganization for tissue at depths of up to 2 mm with good correlation to histology. PS-OCT and accumulated optical phase retardation images of articular cartilage as constructed from alterations in Stokes vector parameters appear to give a valuable but different assessment of alterations in tissue birefringence and organization than have been reported for OCT images obtained with the use of polarized or non-polarized light sources. This is the first time that alterations in the polarization state of light reflected from within the tissue have been demonstrated to be consistent with changes observed in the orientation and organization of the collagen matrix in advanced stages of DJD. The degree of phase transformation of light reflected from within the tissue as determined by PS-OCT imaging does not appear to be altered by the presence or absence of proteoglycan.

Microaneurysms (MAs) are pathognomonic signs that help clinicians to detect diabetic retinopathy (DR) in the early stages. Automatic detection of MA in retinal images is an active area of research due to its application in screening processes for DR which is one of the main reasons of blindness amongst the working-age population. The focus of these works is on the automatic detection of MAs in en face retinal images like fundus color and Fluorescein Angiography (FA). On the other hand, detection of MAs from Optical Coherence Tomography (OCT) images has 2 main advantages: first, OCT is a non-invasive imaging technique that does not require injection, therefore is safer. Secondly, because of the proven application of OCT in detection of Age-Related Macular Degeneration, Diabetic Macular Edema, and normal cases, thanks to detecting MAs in OCT, extensive information is obtained by using this imaging technique. In this research, the concentration is on the diagnosis of MAs using deep learning in the OCT images which represent in-depth structure of retinal layers. To this end, OCT B-scans should be divided into strips and MA patterns should be searched in the resulted strips. Since we need a dataset comprising OCT image strips with suitable labels and such large labelled datasets are not yet available, we have created it. For this purpose, an exact registration method is utilized to align OCT images with FA photographs. Then, with the help of corresponding FA images, OCT image strips are created from OCT B-scans in four labels, namely MA, normal, abnormal, and vessel. Once the dataset of image strips is prepared, a stacked generalization (stacking) ensemble of four fine-tuned, pre-trained convolutional neural networks is trained to classify the strips of OCT images into the mentioned classes. FA images are used once to create OCT strips for training process and they are no longer needed for subsequent steps. Once the stacking ensemble model is obtained, it will be used to classify the OCT strips in the test process. The results demonstrate that the proposed framework classifies overall OCT image strips and OCT strips containing MAs with accuracy scores of 0.982 and 0.987, respectively.

Aims/Purpose: The detection of subretinal fluid (SRF) and intraretinal fluid (IRF) in optical coherence tomography (OCT) images plays a crucial role in the diagnosis and treatment of certain eye diseases. In this study, we investigated the performance of a Transfer Learning artificial intelligence (AI) technique, which we used to perform the model adaptation from the domain of Heidelberg OCT images to Optopol devices.Methods: A data set of 133 Optopol OCT images. 69 images indicating subretinal or intraretinal fluid and 64 fluid‐free images, were analysed. The AI algorithm that was initially trained on OCT images from Heidelberg device was fine‐tuned to perform the biomarker segmentation in Optopol (Revo NX, SOCT Copernicus REVO, REVO FC) OCT images. Manual assessments by the medical experts were used to evaluate the algorithm's performance.Results: Our findings demonstrate the promising performance of the domain‐adapted model. in detecting SRF and IRF, when initially trained on OCT images from a different device. The algorithm achieved an accuracy of 80% while classifying the presence versus absence of the fluids on the balanced test data set.Conclusions: The study demonstrates a successful application of a transfer learning technique for detection of subretinal and intraretinal fluids in OCT images acquired with the Optopol devices, indicating its potential for enhancing eye diagnostics. Further studies utilizing larger data sets, further biomarkers and diverse OCT devices are warranted to validate the algorithm's robustness and generalizability.

High-Definition and 3-dimensional Imaging of Macular Pathologies with High-speed Ultrahigh-Resolution Optical Coherence Tomography

To investigate morphological variations in the macular area with optical coherence tomography (OCT) after vitrectomy for diabetic fibrovascular proliferation. We reviewed 108 cases using OCT 7-15 months after vitrectomy. Of these, 32 received OCT within 3 months postoperatively. Morphological variations were categorized and correlated with visual outcome. Only 24 cases (21.4%) had no obvious abnormalities. The most frequent findings were epiretinal membrane (52.8%), macular thickening (37.0%) and macular cysts (28.7%). Multivariate regression showed that diffuse macular thickening, loss of foveal depression and diffuse retinal thinning were significantly associated with poor visual acuity. Sequential OCT (< 3 and >or= 7 months) revealed that epiretinal membrane and oedema outside of fovea changed significantly between two examinations. OCT may identify diverse morphological changes in the macular area after diabetic vitrectomy for fibrovascular proliferation. Macular appearance may change over time, and certain types of morphological changes may be associated with poor visual function.

Aim: To investigate and compare the presentation of granulomatous lesions in optical coherence tomography (OCT) images and compare this to previous studies of nonmelanoma skin tumors. Methods: Two patients with granulomas, tophi and granuloma annulare (GA), respectively, were photographed digitally, OCT-scanned and biopsied in the said order. Normal skin was OCT-scanned for comparison, but not biopsied. The OCT images from each lesion were compared with their histologic images as well as with OCT images with similar characteristics obtained from nonmelanoma skin tumors. Results: The OCT images of the tophi showed hyperreflective, rounded cloud-like structures in dermis, their upper part sharply delineated by a hyporeflective fringe. The deeper areas appeared blurred. The crystalline structures were delineated by a hyporeflective fringe. OCT images of GA showed two different structures in dermis: a hyporeflective rounded one, and one that was lobulated and wing-like. Conclusion: Granulomatous tissue surrounding urate deposits appeared as a clear hyporeflective fringe surrounding a light, hyperreflective area. The urate crystals appeared as hyperreflective areas, shielding the deeper part of dermis, meaning OCT could only visualize the upper part of the lesions. The lobulated, wing-like structure in GA may resemble diffuse GA or a dense lymphocytic infiltrate as seen on histology. The rounded structure in GA may represent an actual granuloma or either diffuse GA or a dense lymphocytic infiltrate as described above. This case suggests that OCT images granulomatous tissue as absorbent, hyporeflective areas, and urate crystals appear as reflective areas, obscuring the underlying tissue. In GA a new image shape looking like a wing has been found. The frequency, specificity and sensitivity of this new pattern in OCT imaging will require further studies.

To train generative adversarial network (GAN) models to generate predictive optical coherence tomography (OCT) images of central serous chorioretinopathy (CSC) at 3months after observation using multi-modal OCT images. Four hundred forty CSC eyes of 440 patients who underwent Cirrus OCT imaging were included. Baseline OCT B-scan images through the foveal center, en face choroid, and en face ellipsoid zone were collected from each patient. The datasets were divided into training and validation (n = 390) and test (n = 50) sets. The input images for each model comprised either baseline B-scan alone or a combination of en face choroid and ellipsoid zones. Predictive post-treatment OCT B-scan images were generated using GAN models and compared with real 3-month images. Of 50 generated OCT images, there were 48, 47, and 48 acceptable images for UNIT, CycleGAN, and RegGAN, respectively. In comparison with real 3-month images, the generated images showed sensitivity, specificity, and positive predictive values (PPV) for residual fluid in the ranges of 0.762-1.000, 0.483-0.724, and 0.583-0.704; for pigment epithelial detachment (PED) of 0.917-1.000, 0.974-1.000, and 0.917-1.000; and for subretinal hyperreflective material (SHRM) of 0.667-0.778, 0.925-0.950 and 0.700-0.750, respectively. RegGAN exhibited the highest values except for sensitivity. GAN models could generate prognostic OCT images with good performance for prediction of residual fluid, PED, and SHRM presence in CSC. Implementation of the models may help predict disease activity in CSC, facilitating the establishment of a proper treatment plan.

Extracting optical properties of tissue [e.g., the attenuation coefficient () and the backscattering fraction] from the optical coherence tomography (OCT) images is a valuable tool for parametric imaging and related diagnostic applications. Previous attenuation estimation models depend on the assumption of the uniformity of the backscattering fraction () within layers or whole samples, which does not accurately represent real-world conditions. Our aim is to develop a robust and accurate model that calculates depth-wise values of attenuation and backscattering fractions simultaneously from OCT signals. Furthermore, we aim to develop an attenuation compensation model for OCT images that utilizes the optical properties we obtained to improve the visual representation of tissues. Using the stationary iteration method under suitable constraint conditions, we derived the approximated solutions of and on a single scattering model. During the iteration, the estimated value of can be rectified by introducing the large variations of , whereas the small ones were automatically ignored. Based on the calculation of the structure information, the OCT intensity with attenuation compensation was deduced and compared with the original OCT profiles. The preliminary validation was performed in the OCT A-line simulation and Monte Carlo modeling, and the subsequent experiment was conducted on multi-layer silicone-dye- phantoms and ex vivo cow eyes. Our method achieved robust and precise estimation of and for both simulated and experimental data. Moreover, corresponding OCT images with attenuation compensation provided an improved resolution over the entire imaging range. Our proposed method was able to correct the estimation bias induced by the variations of and provided accurate depth-resolved measurements of both and simultaneously. The method does not require prior knowledge of the morphological information of tissue and represents more real-life tissues. Thus, it has the potential to help OCT imaging based disease diagnosis of complex and multi-layer biological tissue.

Retinal drawings are a valuable tool allowing for easy visual communication of ophthalmoscopic findings despite less frequent use today in the era of digital medical records and abundance of imaging options (Schachat et al. 2018). For rhegmatogenous retinal detachments (RRD), drawings of retinal breaks and degree of detachment can aid patient management. In a RRD with an intact fovea, the distance of a detachment from the fovea indicates the distance that ensures central visual acuity, as fovea-off RRD are at risk of a worse visual outcome (Salicone et al. 2006; Hajari et al. 2014; Rezar et al. 2016). Communicating the distance from the RRD border to the fovea to the patient as well as other healthcare personnel can likely improve outcomes especially since patient movement has shown to cause retinal detachment progression (de Jong et al. 2017). This study examines the subjective/objective discrepancy or whether the degree of detachment is communicated accurately by comparing the user-dependent slit-lamp and/or indirect ophthalmoscopy findings to optical coherence tomography (OCT) images taken immediately after diagnosis. For this study, we solely view the degree of detachment as distance from the RRD border to the fovea. Retinal drawings were obtained from fovea-on RRD patients participating in a prospective study (ClinicalTrials.gov Identifier: NCT03655652) at the Department of Ophthalmology, at Rigshospitalet – Glostrup, Denmark. The retinal drawings were either drawn digitally or on paper by ophthalmology residents. The shortest distance from the retinal detachment border on a drawing to the fovea was measured with Fiji imagej software (v. 1.52 g) (https://fiji.sc). For each retinal drawing, we measured the corresponding distance on OCT images (Heidelberg Spectralis, Heidelberg Engineering, Heidelberg, Germany) taken immediately after examination and retinal drawing. The shortest distance on OCT between fovea and the RRD border was measured with built-in software (heidelberg eye explorer, v. 1.9.10.0, Heidelberg Engineering, Heidelberg, Germany). Patients with an RRD > 10 mm from the fovea were excluded as our digital template for retinal drawings only allows the RRD border to be within 10 mm of the fovea. r (v. 3.3.2, R Foundation for Statistical Computing, Vienna, Austria) was used for statistical analysis. From 59 patients, 45 retinal drawings were available – 43 drawn digitally and two drawn on paper. Two patients were excluded for exceeding the 10 mm RRD border distance to the fovea. Figure 1 A depicts the correlation between the retinal drawings and the objective OCT distance taken immediately after examination. Retinal drawings deviated significantly from the ideal no difference between drawing and objectively measured RRD border distance from the fovea (p < 0.0001). A split-fovea patient would on average be drawn 3.31 mm from the fovea, whereas an RRD border 6.0 mm from the fovea would be drawn 4.32 mm from the fovea. Almost half of the patients (20/43, 46.5%) had routine OCT performed prior to examination (TOPCON OCT 3D 2000 – 6 × 6 mm macular scan) (Topcon Corporation, Tokyo, Japan) with the RRD border visible in 13 of these scans. The fovea threatening RRDs visualized on OCT were somewhat more accurately identified; a split fovea would on average be drawn 2.05 mm from the fovea if OCT was available. Although OCT seemed to aid in more accurate retinal drawings, it did not represent a significant improvement over no OCT visualization of the RRD (p = 0.175). Thus, with retinal drawings it is worth noting that RRDs close to the fovea are at risk of being labelled as far away and vice versa. We suspect that the bullous components of the RRD draw attention while flatter components are easier to miss. We suggest that the OCT be used more actively in RRD diagnosis to accurately communicate the RRD status to the patient and other healthcare personnel as well as aid ophthalmology residents in accurately interpreting ophthalmoscopic findings.

BackgroundRecent research on macular diseases has prompted investigations into the condition of the intersection between the photoreceptor inner and outer segments (IS/OS) and the relationship with retinal photoreceptor abnormalities. Although the origin of the IS/OS in optical coherence tomography (OCT) images is unclear, it may be related to either the cellular activity of the photoreceptors or the structure of the OS disks. To address this question, we compared the IS/OS status in OCT images of rat retinas before and after euthanasia.MethodsOCT images were taken before and after euthanasia in four eyes of two Brown Norway rats. After the OCT images were taken, the rats were used for histopathological studies to confirm that retinal structures were intact.ResultsBefore euthanasia, the IS/OS and external limiting membrane (ELM) line were clearly identifiable on the OCT images. However, after euthanasia, neither the IS/OS nor the ELM line was evident in three out of four eyes, and a faint IS/OS and an ELM line were identified in one eye. Histopathological analysis did not show any abnormalities in the retina in any of the four eyes.ConclusionThe origin of the IS/OS identified in OCT images is likely related to the biological activities of the photoreceptor cells.

Structural Features Associated With the Development and Progression of RORA Secondary to Maternally Inherited Diabetes and Deafness

This work investigates combination of Optical Coherence Tomography and two cameras, observing a microscopic scene. Stereo vision provides realistic images, but is limited in terms of penetration depth. Optical Coherence Tomography (OCT) enables access to subcutaneous structures, but 3D-OCT volume data do not give the surgeon a familiar view. The extension of the stereo camera setup with OCT imaging combines the benefits of both modalities. In order to provide the surgeon with a convenient integration of OCT into the vision interface, we present an automated image processing analysis of OCT and stereo camera data as well as combined imaging as augmented reality visualization. Therefore, we care about OCT image noise, perform segmentation as well as develop proper registration objects and methods. The registration between stereo camera and OCT results in a Root Mean Square error of 284 μm as average of five measurements. The presented methods are fundamental for fusion of both imaging modalities. Augmented reality is shown as application of the results. Further developments lead to fused visualization of subcutaneous structures, as information of OCT images, into stereo vision.