Search

OBJECTIVE To compare image quality and acquisition time of corneal and retinal spectral domain optical coherence tomography (SD-OCT) under 3 different sedation-anesthesia conditions in horses. ANIMALS 6 middle-aged geldings free of ocular disease. PROCEDURES 1 randomly selected eye of each horse was evaluated via SD-OCT under the following 3 conditions: standing sedation without retrobulbar anesthetic block (RB), standing sedation with RB, and general anesthesia with RB. Five regions of interest were evaluated in the cornea (axial and 12, 3, 6, and 9 o’clock positions) and fundus (optic nerve head). Three diagnostic scans of predetermined quality were obtained per anatomical region. Image acquisition times and total scans per site were recorded. Corneal and retinal SD-OCT image quality was graded on a subjective scale from 0 (nondiagnostic) to 4 (excellent). RESULTS Mean values for the standing sedation without RB, standing sedation with RB, and general anesthesia conditions were 24, 23, and 17, respectively, for total cornea scan attempts; 23, 19, and 19 for total retina-scan attempts; 14.6, 13.2, and 9.2 minutes for total cornea scan time; 19.1, 9.2, and 13.0 for total retina scan time; 2.0, 2.3, and 2.5 for cornea grade; and 2.7, 2.9, and 2.5 for retina grade. CONCLUSIONS AND CLINICAL RELEVANCE The RB facilitated globe akinesia and improved the percentage of scans in frame and region of interest accuracy for retinal imaging via OCT in horses. Retrobulbar blocks improved clinical image acquisition while minimizing motion artifact.

Background: In ophthalmology, thickness and vessel density (VD) measurements for the 6 x 6 mm inner macular retinal area have received increasing attention in glaucomatous progression research. For this area, the Angiovue optical coherence tomography system introduced a 304 x 304 A/B scans function (classic Angio Retina scan) in 2014, and a 400 x 400 A/B scans function (high-definition [HD] Angio Retina scan) in 2017. These scan types cannot be used in combination for the software provided for progression analysis.Purpose: Since losing data for 3 years may negatively influence progression analysis, we investigated whether clinically significant differences exist between consecutive measurements acquired with these scan types on the same eyes.Methods: As a part of our noninterventional prospective glaucoma imaging study, primary-open-angle glaucoma patients (POAG group), and ocular hypertensive and healthy control participants (structurally undamaged group) were imagedusing both the classic and the HD Angio Retina scans, respectively, without changing the patients’ position. High-quality images were obtained on 12 POAG eyes of 12 consecutive POAG patients, and 10 healthy and ocular hypertensive eyes of 10 consecutive participants before the data collection had to be suspended due to the new coronavirus epidemic.Results: For Early Treatment Diabetic Retinopathy Study image area, the mean difference (classic minus HD value) was 0.02 ± 0.37 μm for inner retinal thickness (P = 0.869) and 0.33 ± 1.33 % (P = 0.452) for superficial capillary VD in the structurally normal group (between-methods difference: ≤ 0.8% of the respective normal value). In the POAG group, the corresponding figures were -0.07 ± 1.22 μm for inner retinal thickness (P = 0.854; between-methods difference: 0.6% of the normal value) and 1.12 ± 2.58 % for superficial capillary VD (P = 0.158; classic scan value minus HD scan value: 1.12 ± 2.58 %; 2.3% of the normal value).Conclusion: Our results suggest that combined use of thickness and VD values for structurally normal eyes and thickness values for POAG eyes derived from classic and HD scans, respectively, for progression analysis can be reasonable since the differences between the corresponding values are small. However, combining the corresponding VD parameters for POAG eyes is useful only when the follow-up time before the scan type change is long enough to counterbalance the effect of the change on the result.

Heart disease continues to be the leading cause of death in the USA. Deep learning-based artificial intelligence (AI) methods have become increasingly common in studying the various factors involved in cardiovascular disease. The usage of retinal scanning techniques to diagnose retinal diseases, such as diabetic retinopathy, age-related macular degeneration, glaucoma and others, using fundus photographs and optical coherence tomography angiography (OCTA) has been extensively documented. Researchers are now looking to combine the power of AI with the non-invasive ease of retinal scanning to examine the workings of the heart and predict changes in the macrovasculature based on microvascular features and function. In this review, we summarize the current state of the field in using retinal imaging to diagnose cardiovascular issues and other diseases.

Recently, holographic optics such as volume holographic optical elements (vHOEs) receive increasing attention as optical combiners in augmented reality (AR) applications. Especially vHOEs fabricated by means of wave front printing have the potential to realize complex optical functions with high diffraction efficiency while maintaining excellent transmittance. We present the recording of a holographic combiner for AR applications fabricated by means of individually modulated recording wave fronts in our extended immersion-based holographic wave front printer setup. Holographic elements from our setup are made up of individual sub-holograms, so called Hogels. The implementation of two phase-only reflective spatial light modulators (SLMs) allows for the recording of Hogels and consequently vHOEs in a wide range of different configurations. Large-area vHOEs are achieved by adjacent recording of multiple Hogels in a step-wise fashion. Our immersion-based printer setup ensures a high numerical aperture for the recording configuration, which is directly linked to a wide angular range of possible replay configurations for wave front propagation in air. We present a reflective vHOE realizing a large off-axis to on-axis wave front transformation suitable as holographic combiner for retinal scanning displays. The vHOE is characterized by evaluating the diffractive properties of the hologram’s volume gratings, as well as investigating the vHOE’s combiner characteristics by means of field of view (FoV) and eye box size evaluation.

This study aims the impostor is a very cunning person who reaches an obsessive stage to perfection in impersonating someone in actual life, concentrates on his biometric. He analyzes the controls, restrictions, and obstacles that he will face to overcome them. The technologies biometric recognition performs a greatly important role in impostor detection. Biometrics properties refer to the automatic recognition of persons depending on their behavioral and physiological characteristics. Biometrics comprises face recognition, fingerprint, voice recognition, retinal scanning, and so on. Biometrics may increment the reliability of an ID card system. In this paper, a review of the concepts mentioned above will be provided. At first, a presentation about a procedural overview of biometric recognition technologies, ID card systems. Then dissection will be presented for the review of the most recent techniques. A description of each concept will be given and a comparison study is achieved with formal discussion and analysis for each approach result introduces in this study. Finally, a summary of the research results is given.

Retinal blood vessels are one of the most significant features in the fundus image of the eye, which plays a crucial role in the early screening of different ocular diseases like glaucoma, diabetic retinopathy, cataract and hypertensive retinopathy. Also in the area of biometric systems, blood vessel structure plays a vital role as retina scan is one of the finest and reliable methods. This paper proposed a segmentation technique which accurately extracts retinal blood vessels. The proposed algorithm conducted in three phases (i) pre -processing of image using AHE, CLAHE and average filtering, (ii) Multi-threshold based novel segmentation technique is used and (iii) post processing is done to remove the imperfections and for this morphological operation is employed. This method efficiently segments the vessels and improves the performance parameters. The accuracy of 95.3% is achieved. Implementation part was done in MATLAB 2015a using a DRIVE database openly available online.

Background: Optical Coherence Tomography (OCT) is a non-invasive medical imaging technique that provides high-resolution cross-sectional images of the retina. There is a need to develop algorithms for obtaining quantitative and qualitative information about the retina which are essential for assessing and managing eye conditions. Methods: This work emphasizes on an automated image processing algorithm for segmenting retinal layers. It involves preprocessing of the acquired retinal SD-OCT image (B-scan) using the proposed automatic Anisotropic diffusion filter, followed with contrast stretching to suppress intrinsic speckle noise without blurring structural edges. Graph search segmentation using Dijkstra algorithm with a combination of threshold and axial gradient as the cost function is used to segment the retinal layer boundaries. Results: The algorithm was performed and the average thickness of the segmented retina was computed for the 3D retinal scan (128 B-scans) of 8 subjects (4 normal and 4 abnormal) using Early Treatment Diabetic Retinopathy Screening (ETDRS) chart. Conclusion: Segmentation was evaluated using manually segmented B-scan by an Ophthalmologist as ground truth and accuracy was found to be 99.14 ± 0.27%.

Gunduz, Ozgur/0000-0003-1021-5219; WOS: 000433949500001 PubMed: 29843674 Background: Vitiligo is a disease characterized by depigmented macules and patches that occur as a result of the loss of functional melanocytes from the affected skin through a mechanism which has not been elucidated yet. Destruction of pigment cells in vitiligo may not remain limited to the skin; the eyelashes, iris, ciliary body, choroid, retinal pigment epithelium and meninges may also be affected. This study aims to compare the choroidal thickness of patients with and without vitiligo using optical coherence tomography (OCT). Methods: Spectral-domain optical coherence tomography (SD-OCT) (Retina Scan Advanced RS-3000 NIDEK, Japan) instrument (with lambda = 840 nm, 27,000 A-scans/second and 5 mu m axial resolution) was used for the imaging. Statistical analysis was performed using SPSS 21.0 software package. Results: In all values except optic nevre area measurements, the choroidal thickness of all vitiligo patients was found out to be thinner compared to the control group. Conclusions: In vitiligo, the choroidal thickness may be affected by the loss of melanocytes.

Purpose: To evaluate the feasibility and safety of a coaxial dual-wavelength optical coherence tomography (OCT) device (marked as Hydra-OCT). Methods: Healthy participants without ocular pathology underwent retinal imaging using the Hydra-OCT allowing for simultaneous measurement of retinal scanning of 840 and 1,072 nm wavelength. Before and after measurement, best-corrected visual acuity and patients’ comfort were assessed. Representative OCT images from both wavelengths were compared by 5 independent graders using a subjective grading scheme. Results: A total of 30 eyes of 30 participants (8 females and 22 males) with a mean age of 26.5 years (range from 19 to 55 years) were included. Dual-wavelength image acquisition was made possible in each subject. The participant’s effort and comfort assessment using the Hydra-OCT imaging revealed an equivalent value as compared to the commercially available OCT machine. No adverse events were reported, and visual acuity was not altered by the Hydra-OCT. Imaging between the systems was comparable. Conclusions: This study provides evidence for the feasibility and safety of a coaxial dual-wavelength OCT imaging method under real-life conditions. The novel Hydra-OCT imaging device may offer additional insights into the pathology of retinal and choroidal diseases.

The accurate segmentation of retinal layers of the eye in a 3D optical coherence tomography (OCT) data provides relevant clinical information. This chapter introduces a three-dimensional (3D) segmentation approach that uses an adaptive patient-specific retinal atlas as well as an appearance model for 3D OCT data. To reconstruct that atlas of 3D retinal scan, we first segment the central area of the macula at which we can clearly identify the fovea. Markov Gibbs random field (MGRF) including intensity, shape, and spatial information of 12 layers of retina was all used to segment the selected area of retinal fovea. A set of coregistered OCT scans that were gathered from 200 different individuals were used to build a 2D shape prior. This shape prior was adapted in a following step to the first-order appearance and second-order spatial interaction MGRF model. After segmenting the center of the macula “foveal area,” the labels and appearances of the layers that have been segmented were used to have the adjacent slices segmented as well. The last step was then repeated recursively until the 3D OCT scan of the patient is segmented. This approach was tested on 30 individuals while some of them were normal and others were pathological, and then compared to a manually segmented ground truth and finally these results were verified by medical retina experts. Metrics such as dice similarity coefficient, agreement coefficient, and average deviation metrics were used to measure the performance of the proposed approach. Accomplished accuracy by the proposed approach shows promising results with noticeable advantages over the state-of-the-art 3D OCT approach.

The guest editorial provides an introduction to the Special Section on Advanced Retinal Imaging: Instrumentation, Methods, and Applications.

The accurate segmentation of retinal layers of the eye in a 3-D Optical Coherence Tomography (OCT) data provides relevant clinical information. This paper introduces a 3D segmentation approach that uses an adaptive patient-specific retinal atlas as well as an appearance model for 3D OCT data. To reconstruct that atlas of 3D retinal scan, we first segment the central area of the macula at which we can clearly identify the fovea. Markov Gibbs Random Field (MGRF) including intensity, shape, and spatial information of 12 layers of retina were all used to segment the selected area of retinal fovea. A set of co-registered OCT scans that were gathered from 200 different individuals were used to build A 2D shape prior. This shape prior was adapted in a following step to the first order appearance and second order spatial interaction MGRF model. After segmenting the center of the macula “foveal area”, the labels and appearances of the layers that have been segmented were used to have the adjacent slices segmented as well. The last step was then repeated recursively until the a 3D OCT scan of the patient is segmented. This approach was tested on 35 individuals while some of them were normal and others were pathological, and then compared to a manually segmented ground truth and finally these results were verified by medical retina experts. Metrics such as Dice Similarity Coefficient (DSC), agreement coefficient (AC), and average deviation (AD) metrics were used to measure the performance of the proposed approach. Accomplished accuracy by the proposed approach shows promising results with noticeable advantages over the state-of-the-art 3D OCT approach.

Traditional biometric systems (fingerprint, voice, facial recognition, retinal scan, etc) have been considered as the most secure authentication systems for a long period of time. However, recently there have been incidents where these systems were compromised. Even though the traditional biometric systems are successful in uniquely identifying individuals, these biometric credentials can be obtained without the willingness of the person and irrespective of whether the person is alive or dead. Hence more reliable and robust authentication systems are needed in areas where high security is pivotal. Our work involves performing comparative analysis of various approaches for carrying out Brain Biometric Authentication and demonstrating a practical authentication system that can be used for security critical applications.

Accurately identifying and authenticating a human without requiring proximity, yet with high reliability, is crucial for application areas such as surveillance, dynamic authentication, and proof of identity. While a significant research has been conducted in the direction of human authentication, achieving the authentication in an ambient manner, with high reliability, and security is still far from being perfect under the currently deployed methods. This is due to the requirement of a specific posture and approximation to the device in many approved and deployed methods such as fingerprint, facial recognition, and retinal scan. An ambient authentication system is highly dependent on biometric features that can accurately discriminate between one human and another. These biometric features should be insensitive to variation in posture, proximity, and aging. Extraction of a unique feature set that allows a human to be identified smoothly, even without proximity, under varying conditions is one of the main steps needed for an advancement in this field. In this paper, a review of current and emerging mechanism are provided. A proposed method will use a feature set that allows the system to achieve dynamic detection compared to the currently used technologies such as fingerprint, facial recognition and retinal scan. The proposed feature set is made up of a combination of facial minutiae and thermal contours which are extracted from the human face on-the-fly even without the subject coordination.

We developed a clinical ophthalmic prototype by combining bimorph deformable mirror (DM)-based adaptive optics (AO) with a confocal scanning laser ophthalmoscope. A low-cost bimorph DM with a large stroke of 50 μ m and an aperture of 20 mm was utilized to realize a strategy for successive AO control of aberration correction, which permitted open-loop compensation for low-order aberrations and closed-loop correction of high-order aberrations to acceptable root mean square errors of 0.08 μ m in all subjects. Spherical mirrors were folded in a nonplanar configuration to minimize off-axis aberrations and provide a compact, cost-effective design, which achieved a diffraction-limited performance capable of imaging individual photoreceptor cells and blood vessels not only in healthy subjects but also in patients suffering from retinitis pigmentosa. The adaptive optics scanning laser ophthalmoscope (AOSLO) images of the diseased retina had much higher resolutions than those captured by the commercial AO fundus camera, and loss of the photoreceptor mosaic could be distinguished more accurately due to the improvement in resolution. The compact design and easy handling of the bimorph DM-based AO control may facilitate the translation of AOSLO into clinical settings, and this prototype development will continue with future device refinement and extensive clinical testing.

We present Extramission, a method to a large scale interactive virtual environment. It consists of dual head mounted pico projectors and retro-reflective materials. With high-accuracy retro-reflective materials, laser beams scanned on user’s retina makes clear and free-focus vision. In this retinal scanning configuration, even if the luminance of the projector is low, scanned images can be seen clearly, which helps to evade overlaps between projected images. Due to small overlaps, Extramission can provide multi-user virtual experiences showing different images to each individual, and dual pico projectors can provide each user with stereoscopic vision. Moreover, the tolerance of low luminance allows larger distance between users and retro-reflectors, which is required for large scale virtual experiences using head mounted projectors. In this paper, we describe the principle and the implementation of Extramission. We also see its performance of displaying images.

It has been recently demonstrated that structures corresponding to the cell bodies of highly transparent cells in the retinal ganglion cell layer could be visualized noninvasively in the living human eye by optical coherence tomography (OCT) via temporal averaging. Inspired by this development, we explored the application of volumetric temporal averaging in mice, which are important models for studying human retinal diseases and therapeutic interventions. A general framework of temporal speckle-averaging (TSA) of OCT and optical coherence tomography angiography (OCTA) is presented and applied to mouse retinal volumetric data. Based on the image analysis, the eyes of mice under anesthesia exhibit only minor motions, corresponding to lateral displacements of a few micrometers and rotations of a fraction of 1 deg. Moreover, due to reduced eye movements under anesthesia, there is a negligible amount of motion artifacts within the volumes that need to be corrected to achieve volume coregistration. In addition, the relatively good optical quality of the mouse ocular media allows for cellular-resolution imaging without adaptive optics (AO), greatly simplifying the experimental system, making the proposed framework feasible for large studies. The TSA OCT and TSA OCTA results provide rich information about new structures previously not visualized in living mice with non-AO-OCT. The mechanism of TSA relies on improving signal-to-noise ratio as well as efficient suppression of speckle contrast due to temporal decorrelation of the speckle patterns, enabling full utilization of the high volumetric resolution offered by OCT and OCTA.

Fundus cameras are the current clinical standard for capturing retinal images, which are used to diagnose a variety of sight-threatening conditions. Traditional fundus cameras are not easily transported, making them unsuitable for field use. In addition, traditional fundus cameras are expensive. Due to this, a variety of technologies have been developed such as the D-EYE Digital Ophthalmoscope (D-EYE Srl, Padova, Italy) which is compatible with various cellphone cameras. This paper reports on the comparison of the image quality of the Nidek RS-330 OCT Retina Scan Duo (Nidek, Tokyo, Japan) and the D-EYE paired with an iPhone 6 (Apple, Cupertino, USA). Twenty-one participants were enrolled in the study of whom 14 underwent nonmydriatic and mydriatic imaging with the D-EYE and the Nidek. Seven participants underwent nonmydriatic imaging with the D-EYE and the Nidek. The images were co-registered and cropped so that the region of interest was equal in both the D-EYE and Nidek images, as the D-EYE had a smaller field of view. Using the Nidek image as the reference, objective full-reference image quality analysis was performed. Metrics such as structural similarity index and peak signal noise ratio were obtained. It was found that the image quality of the D-EYE is limited by the attached iPhone camera, and is lower when compared to the Nidek. Quantification of the differences between the D-EYE and Nidek allows for targeted development of smartphone camera attachments that can help to bridge the current gap in image quality.

Biometrics finds a lot of application in the modern day security aspects whether it may be in industrial sector, defense sector or in domestic sectors. Entry of a person into an organisation in the work environment plays a very important role as unauthorized persons if entered into a premises may create a flutter & inviable to some terrorist attacks. Hence, biometrics of an authorized person into the work environment plays a very important role. There are a large number of biometric methods for identification, viz., physiological & behavioural. Some of them are face, fingerprint, iris, voice, hand, thumb, ear, vein, gait, code, password, signature, pattern, palm print, etc. As there are a number of biometric methods for the automatic detection of human beings, retina scan is being considered as the biometric identity in the research work undertaken by us because of a large number of advantages over the other biometric identities. For biometric recognition of a person using retina scans, a number of methods exists in the literature. In this context, fractal dimension method is one of the method that could be used. Hence, the retinal recognition is performed in our proposed work for identifying the person by developing new approaches using Fractal Dimension methodologies. Hybrid algorithms are to be prepared & finally the developed codes are going to be run which are going to be performed in the Matlab environment, the simulation results are going to be observed and compared with the research work done by alternate scientists & engineers till now in order to build up the amazingness of the works done by us. This article gives the info about the exhaustive summary of the work carried out by us & that is going to be done along with the methodology that is going to be used for solving the desired objective and arrive at the outcome.

A compact full color laser beam scanning (LBS)-based Augmented Reality (AR) near-eye display has been developed. By the unique relay optical system adopting a novel holographic grating to compensate the color dispersion of holographic image combiner in front of the eye, we have achieved high resolution (1280x720p), large field of view (47degree diagonal), high transparency (over 85%) and hand-held miniaturization. The prototype implemented only two connectors of USB Type-C and HDMI Type-D to supply power and video signal of HDMI interface respectively from small control box using two cables.

Optical coherence tomography (OCT) is the gold standard for quantitative ophthalmic imaging. The majority of commercial and research systems require patients to fixate and be imaged in a seated upright position, which limits the ability to perform ophthalmic imaging in bedridden or pediatric patients. Handheld OCT devices overcome this limitation, but image quality often suffers due to a lack of real-time aiming and patient eye and photographer motion. We describe a handheld spectrally encoded coherence tomography and reflectometry (SECTR) system that enables simultaneous en face reflectance and cross-sectional OCT imaging. The handheld probe utilizes a custom double-pass scan lens for fully telecentric OCT scanning with a compact optomechanical design and a rapid-prototyped enclosure to reduce the overall system size and weight. We also introduce a variable velocity scan waveform that allows for simultaneous acquisition of densely sampled OCT angiography (OCTA) volumes and widefield reflectance images, which enables high-resolution vascular imaging with precision motion-tracking for volumetric motion correction and multivolumetric mosaicking. Finally, we demonstrate in vivo human retinal OCT and OCT angiography (OCTA) imaging using handheld SECTR on a healthy volunteer. Clinical translation of handheld SECTR will allow for high-speed, motion-corrected widefield OCT and OCTA imaging in bedridden and pediatric patients who may benefit ophthalmic disease diagnosis and monitoring.

Polarised near-infra-red light is reflected from the foveal area in a detectable bow-tie pattern of polarisation states, offering the opportunity for eye tracking. A coaxial optical transducer was developed, consisting of a laser diode, a polariser, a filter, and a photodetector. Several such transducers may be used to interrogate different spots on the retina, thus eliminating the requirement for scanning systems with moving parts. To test the signal quality obtainable, using just one transducer, a test subject was asked to fixate successively on twelve targets located on a circle around the transducer, to simulate the retina’s being interrogated by twelve sensors placed on a 30 diameter circle surrounding the projection of the fovea. The resulting signal is close to the “ideal” sine wave that would have been recorded from a propeller-type birefringence pattern from a human fovea. The transducer can be used in the detection of fixation for medical and other purposes. It does not require calibrati...

The paradigm of embedding computing devices in our surrounding environment has gained more interest in recent days. Along with contemporary technology comes challenges, the most important being the security and privacy aspect. Keeping the aspect of compactness and memory constraints of pervasive devices in mind, the biometric techniques proposed for identification should be robust and dynamic. In this work, we propose an emerging scheme that is based on few exclusive human traits and characteristics termed as ocular biometrics, promising utmost security and reliability. Complex iris recognition and retinal scanning algorithms have been discussed which promises achievement of accurate results. The performance and vast applications of these algorithms on pervasive computing devices is also addressed.

The identification of an individual is one of the main applications of forensic science, used in legal settings for deciding cases in courts of law. Different methods have been developed for the identification of a person, including fingerprints, DNA profiling, retina scan, facial features and many others. The reliable and accurate identification mainly relies upon substantial variability of structures and features of evidence corresponding to reference material. During the last decade, human identification through hand vein patterns has been focused in various studies and shown promising results. However, most of the reported methods require extensive human efforts for manual feature calculation. Herein, we propose a novel identification tool namely ADVIT for the identification of humans based on their dorsum veins pattern. The samples of the dorsum of the right or left hand were collected from 50 participants in the form of images. Initially, images were preprocessed and noise (in terms of hair on the skin and other details) was removed. Later on, the vein skeleton was extracted from the preprocessed images and a binary image of veins pattern (veins in the foreground and every other detail as background) was generated. Two different types of the feature were computed and based on these features, three different experiments were performed and the evaluation metrics were computed. Merging of hand-crafted grid-based features and deep representation from RESNET-50 showed maximum results in terms of Sensitivity (0.8803), Specificity (0.8890), Precision (0.8849), False Positive Rate (0.1074), Accuracy (0.8861), F1 Score (0.8817), and MCC (0.7636). These results depicted that the model is accurate and sensitive for identification through dorsum veins pattern. The proposed model can aid forensic scientists to identify perpetrator using hand images. ADVIT is freely available at ( http://zeetu.org/advit.html ).

Early diagnosis of glaucoma, which is a leading cause for visual impairment, is critical for successful treatment. It has been shown that Imaging polarimetry has advantages in early detection of structural changes in the retina. Here, we theoretically and experimentally present a snapshot Mueller Matrix Polarimeter fundus camera, which has the potential to record the polarization-altering characteristics of retina with a single snapshot. It is made by incorporating polarization gratings into a fundus camera design. Complete Mueller Matrix data sets can be obtained by analyzing the polarization fringes projected onto the image plane. In this paper, we describe the experimental implementation of the snapshot retinal imaging Mueller matrix polarimeter (SRIMMP), highlight issues related to calibration, and provide preliminary images acquired from the camera.

Worldwide retinal diseases are found to be frequent cause of vision loss. Early diagnosis of the patient’s Eyes can prevent this. This review paper describes the methodology which uses various image processing and machine learning techniques for the early diagnosis of Glaucoma, Macular degeneration, Retinitis Pigmentosa, Stargardt Disease using fundus images based on its symptoms. These techniques include Image Pre-processing, Localization of Optic Nerve Head, CNN Based Classification of Disease.

Purpose To study a novel and fast optical coherence tomography (OCT) device for home-based monitoring in age-related macular degeneration (AMD) in a small sample yielding sparse OCT (spOCT) data and to compare the device to a commercially available reference device. Methods In this prospective study, both eyes of 31 participants with AMD were included. The subjects underwent scanning with an OCT prototype and a spectral-domain OCT to compare the accuracy of the central retinal thickness (CRT) measurements. Results Sixty-two eyes in 31 participants (21 females and 10 males) were included. The mean age was 79.6 years (age range, 69-92 years). The mean difference in the CRT measurements between the devices was 4.52 μm (SD ± 20.0 μm; range, -65.6 to 41.5 μm). The inter- and intrarater reliability coefficients of the OCT prototype were both >0.95. The laser power delivered was

Diabetic Retinopathy (DR) is a medical condition caused by fluctuating insulin level in the blood which causes vision loss in case of severity. Timely treatment of such risks requires identification of the first clinical symptoms like microaneurysms (MAs) and hemorrhages (HMAs). The presence of those symptoms are visible in the digital color photographs of the retina and appear as round dark red spots in the image. In this paper, two approaches in the detection of MAs and HMAs are proposed. First, the semi automated approach applies semi automated hessian-based candidate selection algorithm (SHCS) followed by thresholding to detect true MAs and HMAs. The automated approach applies automated hessian-based candidate selection algorithm (AHCS) followed by feature extraction and SVM classification that uses twenty images for training manually annotated by medical domain experts. Implementations of both the approaches have been tested on real world images from retinal scan. From the results, the detection rate of automated algorithm when compared with that of the semi automated algorithm has been found to be significantly lesser with a probability p

We show for the first time FF-OCT combined with SD-OCT for real time matching of the optical path length of FF-OCT to demonstrate high resolution en face retinal imaging.

Conventional scanning laser ophthalmoscopy (SLO) utilizes a finite collection pinhole at a retinal conjugate plane to strongly reject out-of-focus light while primarily transmitting the in-focus, retinal backscattered signal. However, to improve lateral resolution, a sub-Airy disk collection pinhole is necessary, which drastically reduces the signal-to-noise ratio (SNR) of the system and is thus not commonly employed. Recently, an all-optical, super-resolution microscopy technique known as optical photon reassignment (OPRA) microscopy (also known as re-scan confocal microscopy) has been developed to bypass this fundamental tradeoff between resolution and SNR in confocal microscopy. We present a methodology and system design for obtaining super resolution in retinal imaging by combining the concepts of SLO and OPRA microscopy. The resolution improvement of the system was quantified using a 1951 USAF target at a telecentric intermediate image plane. Retinal images from human volunteers were acquired with this system both with and without using the OPRA technique to demonstrate the resolution improvement when imaging parafoveal cone photoreceptors. Finally, we quantified the resolution improvement in the retina by analyzing the radially averaged power spectrum of the retinal images.

Optical coherence tomography (OCT) has become standard in retinal imaging at the pre-clinical and clinical level by allowing non-invasive, three-dimensional imaging of the tissue structure. However, OCT lacks specificity to contrast agents that could be used for in vivo molecular imaging. We have performed in vivo photothermal optical coherence tomography (PT-OCT) of targeted gold nanorods in the mouse retina after the mice were injected systemically with the contrast agent. To our knowledge, we are the first to perform PT-OCT in the eye and image targeted gold nanorods with this technology. As a model of age-related wet macular degeneration, lesions were induced by laser photocoagulation in each mouse retina (n=12 eyes). Untargeted and targeted (anti-mouse CD102 antibody, labeling neovasculature) gold nanorods (peak absorption λ=750nm) were injected intravenously by tail-vein injection five days after lesion induction, and imaged the same day with PT-OCT. Our instrument is a spectral domain OCT system (λ=860nm) with a Titanium:Sapphire laser (λ=750nm) added to the beam path using a 50:50 coupler to heat the gold nanorods. We acquired PT-OCT volumes of one lesion per mouse eye. There was a significant increase in photothermal intensity per unit area of the lesion in the targeted gold nanorods group versus the saline control group and the untargeted gold nanorods group. This experiment demonstrates the feasibility of PT-OCT to image the distribution of molecular contrast agents in the mouse retina, including in highly scattering lesions. In the future we will use this method to identify new biomarkers linked with retinal disease.

With the increasing concern over information security, the demand for effective biometric recognition modalities has increased. In addition, more biometric recognition modalities are currently under development. This paper overviews and compares several biometric recognition technologies such as finger-scan, facial scan, retinal scan, hand geometry, and signature authentication. Some of the continuing challenges for biometric modalities are to provide accurate results within an acceptable time limit and to define the environment in which the technology provides the strongest benefit to individuals and institutions. For the security officer, the challenge is to demonstrate to upper management that the benefits of implementation outweigh its risks and costs. Among the reviewed techniques, some recognition techniques were found to have high accuracy at varying costs, while the DNA modality was found to be the most secure technique and most expensive.

Adaptive optics (AO) is essential for achieving diffraction limited resolution in large numerical aperture (NA) in-vivo retinal imaging in small animals. Cellular-resolution in-vivo imaging of fluorescently labeled cells is highly desirable for studying pathophysiology in animal models of retina diseases in pre-clinical vision research. Currently, wavefront sensor-based (WFS-based) AO is widely used for retinal imaging and has demonstrated great success. However, the performance can be limited by several factors including common path errors, wavefront reconstruction errors and an ill-defined reference plane on the retina. Wavefront sensorless (WFS-less) AO has the advantage of avoiding these issues at the cost of algorithmic execution time. We have investigated WFS-less AO on a fluorescence scanning laser ophthalmoscopy (fSLO) system that was originally designed for WFS-based AO. The WFS-based AO uses a Shack-Hartmann WFS and a continuous surface deformable mirror in a closed-loop control system to measure and correct for aberrations induced by the mouse eye. The WFS-less AO performs an open-loop modal optimization with an image quality metric. After WFS-less AO aberration correction, the WFS was used as a control of the closed-loop WFS-less AO operation. We can easily switch between WFS-based and WFS-less control of the deformable mirror multiple times within an imaging session for the same mouse. This allows for a direct comparison between these two types of AO correction for fSLO. Our results demonstrate volumetric AO-fSLO imaging of mouse retinal cells labeled with GFP. Most significantly, we have analyzed and compared the aberration correction results for WFS-based and WFS-less AO imaging.

Optical imaging usually suffers from aberrations that are induced by various structures when imaging biological samples. Usually aberrations degrade the imaging system performances by broadening the point spread function (PSF). Unexpectedly we show that in spatially incoherent interferometry like full-filed optical coherence tomography (FFOCT), the system PSF width is almost insensitive to aberrations. Instead of considering the PSF of a classical imaging system such as a microscope, we specifically pay attention to the system PSF of interferometric imaging systems for which an undistorted wavefront from a reference beam interferes with the distorted wavefront of the object beam. By comparing the cases of scanning OCT with spatially coherent illumination, wide-field OCT with spatially coherent illumination and FFOCT with spatially incoherent illumination, we found that in FFOCT with spatially incoherent illumination the system PSF width is almost independent of the aberrations and only its amplitude varies. This is demonstrated by theoretical analysis as well as numerical calculations for different aberrations, and confirmed by experiments with a FFOCT system. It is the first time to the best of our knowledge that such specific merit of incoherent illumination in FFOCT has been demonstrated. Based on this, the signal level is used as metric in our adaptive optics FFOCT system for retinal imaging. Only the main aberrations (defocus and astigmatism) that are dominating in eye are corrected to improve the signal to noise ratio and the high order aberrations are skipped. This would increase the correction speed thus reducing the imaging time.

Adaptive optics has been successfully applied to cellular resolution imaging of the retina, enabling visualization of the characteristic mosaic patterns of the outer retina. Wavefront sensorless adaptive optics (WSAO) is a novel technique that facilitates high resolution ophthalmic imaging; it replaces the Hartmann-Shack Wavefront Sensor with an image-driven optimization algorithm and mitigates some the challenges encountered with sensor-based designs. However, WSAO generally requires longer time to perform aberrations correction than the conventional closed-loop adaptive optics. When used for in vivo retinal imaging applications, motion artifacts during the WSAO optimization process will affect the quality of the aberration correction. A faster converging optimization scheme needs to be developed to account for rapid temporal variation of the wavefront and continuously apply corrections. In this project, we investigate the Databased Online Nonlinear Extremum-seeker (DONE), a novel non-linear multivariate optimization algorithm in combination with in vivo human WSAO OCT imaging. We also report both hardware and software updates of our compact lens based WSAO 1060nm swept source OCT human retinal imaging system, including real time retinal layer segmentation and tracking (ILM and RPE), hysteresis correction for the multi-actuator adaptive lens, precise synchronization control for the 200kHz laser source, and a zoom lens unit for rapid switching of the field of view. Cross sectional images of the retinal layers and en face images of the cone photoreceptor mosaic acquired in vivo from research volunteers before and after WSAO optimization are presented.

Two-photon excited fluorescence (TPEF) for in-vivo retinal imaging is an emerging tool for vision science. TPEF has multiple benefits in comparison to conventional confocal fluorescence scanning laser ophthalmoscopy for retinal imaging, including better axial resolution and the ability to use infrared excitation light for imaging the highly photosensitive tissue in the retina. TPEF is very sensitive to the focused spot size, which is enlarged by aberrations induced by the refractive elements of the mouse eye when imaging with a large numerical aperture. Our system begins with a femtosecond pulsed laser for two-photon excitation, which is also sufficiently spectrally broadband to allow for an optical coherence tomography (OCT) sub-system to guide aberration correction. The OCT system operated at 1 volumes/second with our custom GPU accelerated real-time processing. Our lens-based optical design features two deformable elements, one with large stroke for focus control on the retina and the other with multiple actuators for aberration correction. Our wavefront-sensorless adaptive optics (SAO) is driven by a modal search with a sharpness quality metric on the en-face OCT image of the selected retinal layer. After optimization, the speed was increased to 10 fps for TPEF imaging to allow for streaming and averaging ~200 frames per image. To demonstrate the system capabilities, we performed in-vivo retinal fluorescein angiography using TPEF. Our results demonstrate depth-resolved aberration correction with the SAO-OCT to increase the TPEF signal intensity. We also present TPEF at multiple vascular layers in the mouse retina alongside the volumetric OCT to localize the vessels.

The en face operating stereomicroscope offers limited depth perception and ophthalmic surgeons must often rely on stereopsis and instrument shadowing to estimate motion in the axial dimension. Recent research and commercial microscope-integrated optical coherence tomography (MIOCT) systems have allowed OCT of live surgery, but these were restricted to real-time cross-sectional (B-scan) imaging which captures limited information about maneuvers that extend over 3D space. We recently reported on a four dimensional (4D: 3D imaging over time) MIOCT and HUD system with real-time volumetric rendering for human ophthalmic surgery, but this 100 kHz OCT system was restricted to 3.3 volumes/sec to achieve sufficient lateral sampling over a 5x5 mm field of view (FOV). In this work, we present a high-speed 4D MIOCT (HS 4D MIOCT) system for volumetric imaging at 800 kHz A-scan rate. The proposed system employs a temporal spectral splitting (TSS) technique in which the spectrum of a buffered 400 kHz OCT system is windowed into sub-spectra to yield A-scans with reduced axial resolution but at a doubled A-scan rate of 800 kHz. The trade-offs of TSS for B-scan and volumetric retinal imaging were characterized in healthy adult volunteers. In addition, porcine eye surgical manipulations were imaged with HS 4D MIOCT imaging at 10.85 volumes/sec with 400x96x340 (X,Y,Z) usable voxels over a 5x5 mm lateral FOV. HS 4D MIOCT was capable of imaging subtle volumetric tissue manipulations with high temporal and spatial resolution using ANSI-limited optical power and is readily translatable to the human operating suite.

Visible light is absorbed by intrinsic chromophores such as photopigment, melanin, and hemoglobin, and scattered by subcellular structures, all of which are potential retinal disease biomarkers. Recently, high-resolution quantitative measurement and mapping of hemoglobin concentrations was demonstrated using visible light Optical Coherence Tomography (OCT). Yet, most high-resolution visible light OCT systems adopt free-space, or bulk, optical setups, which could limit clinical applications. Here, the construction of a multi-functional fiber-optic OCT system for human retinal imaging with

A dual illumination system is proposed for cornea and retina imaging using spectral domain optical coherence tomography (SD-OCT). The system is designed to acquire cornea and retina imaging with dual illumination with limited optics and using a single spectrometer. The beam propagation for cornea and retina imaging in dual illumination enables to acquire the images of different segments. This approach will reduce the imaging time for separate corneal and retinal imaging. The in vivo imaging of both the cornea and retina of a health volunteer shows the feasibility of the system for clinical applications

We present an adaptive-optics optical coherence tomography (AO-OCT) system with 3.4-mm beam diameter. A deformable mirror is used for the correction of two radial Zernike orders (defocus, vertical and oblique astigmatism). The aberrations are corrected sequentially with a Shack-Hartmann wave-front sensor and the deformable mirror. This system fills a gap between a standard clinical 1.2-mm beam diameter OCT system and a 6-mm beam diameter AO-OCT system. We also present 8° by 8° en face OCT images from a patient with macular degeneration. This system has a 25 cm by 50 cm footprint, which makes it considerably smaller to conventional 6-mm beam diameter AO-OCT system. Because of its larger field of view and smaller size, it is likely to be useful in the ophthalmic clinics for high-resolution imaging of the human eye retina.

Diabetes and Cataract are the key causes of retinal blindness for millions of people. Current detection of diabetes and Cataract from retinal images using Fundus camera is expensive and inconvenient since such detection is not portable and requires specialists to perform an operation. This paper presents an innovative development of a low cost Smartphone based intelligent system integrated with microscopic lens that allows patients in remote and isolated areas for regular eye examinations and disease diagnosis. This mobile diagnosis system uses an artificial Neural Network algorithm to analyze the retinal images captured by the microscopic lens to identify retinal disease conditions. The algorithm is first of all trained with infected and normal retinal images using a personal computer and then further developed into a mobile-based diagnosis application for Android environments. The application is optimized by using the rooted method in order to increase battery lifetime and processing capacity. A duty cycle method is also proposed to greatly improve the energy efficiency of this retinal scan and diagnosis system in Smartphone environments. The proposed mobile-based system is tested and verified using two well-known medical ophthalmology databases to demonstrate its merits and capabilities. The evaluation results indicate that the system shows competitive retinal disease detection accuracy rates (>87%). It also offers early detection of retinal diseases and shows great potential to be further developed to identify skin cancer.

We present the optimization of an adaptive optics loop for retinal imaging. Generally, the wave-front is overdetermined compared to the number of corrector elements. The sampling of the sensor can be reduced while maintaining an efficient correction, leading to higher sensitivity, faster correction and larger dynamic range. An analytical model was developed to characterize the link between number of actuators, number of micro-lenses and correction performance. The optimized correction loop was introduced into a scanning laser ophthalmoscope. In vivo images of foveal photoreceptors were recorded and the obtained image quality is equivalent to the state of the art in retinal AO-imaging.

Optical coherence tomography (OCT) retinal imaging contributes to understanding central nervous system (CNS) diseases because the eye is an anatomical “window to the brain” with direct optical access to nonmylenated retinal ganglion cells. However, many CNS diseases are associated with neuronal changes beyond the resolution of standard OCT retinal imaging systems. Though studies have shown the utility of scattering angle resolved (SAR) OCT for particle sizing and detecting disease states ex vivo, a compact SAR-OCT system for in vivo rodent retinal imaging has not previously been reported. We report a fiber-based SAR-OCT system (swept source at 1310 nm ± 65 nm, 100 kHz scan rate) for mouse retinal imaging with a partial glass window (center aperture) for angular discrimination of backscattered light. This design incorporates a dual-axis MEMS mirror conjugate to the ocular pupil plane and a high collection efficiency objective. A muring retina is imaged during euthanasia, and the proposed SAR-index is examined versus time. Results show a positive correlation between the SAR-index and the sub-cellular hypoxic response of neurons to isoflurane overdose during euthanasia. The proposed SAR-OCT design and image process technique offer a contrast mechanism able to detect sub-resolution neuronal changes for murine retinal imaging.