This PDF file contains the front matter associated with SPIE Proceedings Volume 10474, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Neovascularization in diabetic retinopathy (DR) and age-related macular degeneration (AMD) result in severe vision-loss and are two of the leading causes of blindness. The structural, metabolic, and vascular changes underlying retinal neovascularization are unknown and, thus, there is an unmet need to identify mechanisms of pathogenesis and novel anti-angiogenic therapies. Zebrafish is a robust ophthalmological model because its retina has comparable structure to the human retina and its fecundity and life-cycle enable development of mutant phenotypes of human pathologies. Here, we perform multimodal imaging with OCT and fluorescence confocal scanning laser ophthalmoscopy (cSLO) to identify changes in retinal structure and function in a zebrafish model of vascular leakage. Transgenic zebrafish with EGFP tagged plasma protein were imaged longitudinally at six time points over two weeks to visualize vascular perfusion changes from diethylaminobenzaldehyde (DEAB) treatment. Complementary contrast from OCT-A perfusion maps and cSLO imaging of plasma protein EGFP shows vascular occlusions posttreatment. cSLO images confirm presence of vessels despite loss of OCT-A signal. Plasma protein EGFP contrast also shows significant changes in vessel structure as compared to baseline images. OCT structural volumes show empty vessel cross-sections confirming non-perfusion. In addition, we present algorithms for automated biometric identification of OCT datasets using OCT-A vascular patterns in the presence of significant vascular perfusion changes. These results establish a framework for large-scale in vivo assays to identify novel anti-angiogenic compounds and understand the mechanisms ofneovascularization associated with retinal ocular pathologies.

Optical Coherence Tomography Angiography (OCTA) has recently emerged for imaging vasculature in clinical ophthalmology. Yet, apparent OCTA image artifacts remain challenging to interpret. Here, contrast-enhanced OCTA is employed in rats to help explain these apparent artifacts. By quantifying enhancement due to an intravascular contrast agent with rheological and scattering properties that are different from red blood cells (RBCs), OCTA image features are ascribed to specific rheological and scattering properties of RBCs. By imaging pigmented and unpigmented rats at a wavelength where scattering dominates image contrast (1300 nm), the impact of melanosome scattering on OCT and OCTA signals is determined.

We report on laser Doppler perfusion imaging of human retinas using digital holography with near infrared light. The optical signal is obtained by exploiting the Doppler frequency shifts of cross-polarized light. A polarization beam splitter is used to illuminate the retina with a given linear polarization and collect cross-polarized light. The interference pattern is sampled using two detection channels: a 40 Hz sCMOS camera for real-time monitoring, and a 39 kHz CMOS camera to properly sample the Doppler broadened spectrum of the light backscattered by the retina. The holograms are numerically reconstructed by angular spectrum propagation and then processed on sliding windows of 512 images. For each short-time window, the Fourier transformation along the temporal dimension is computed, and the Doppler signal is drawn from the first moment of the high-pass filtered Fourier transformation. In the resulting images, the contrast is derived from the tissue perfusion which is related to both the local speed and concentration of blood cells. The cardiac cycle of retinal vessels is apparent, and choroidal vasculature can also be observed. Further analysis of the vessels frequency signature allowed for the discrimination of retinal and choroidal vessels. The blood flow is sampled with a temporal resolution of 13 ms while the spatial resolution is estimated to be 20 µm and the field of view approximately 2*2 mm.

Optical coherence tomography angiography (OCT-A) is a novel non-invasive imaging technique that provide the visualization of retinal microvasculature. However, the quantification and evaluation of OCT-A are still a challenge for the diagnosis for ophthalmology. Deep convolutional neural network (CNN) architectures were initially designed for the task of natural image classification, delivering promising precision in computer vision tasks and recent research has applied deep CNN to biomedical image processing tasks and produces impressive outcomes. However, so far, there is no report relating to the application of large deep neural networks on a small annotated OCT-A dataset. We collected and annotated OCT-A datasets that contain diabetic retinopathy (DR), uveitis, dry age-related macular degeneration (AMD) patients, and normal cases. We propose a transfer learning CNN model for automated disease classification using clinical OCT-A images. The CNN model is pre-trained on the ImageNet dataset and fine-tuned the top feedforward layers of the model to fit the classification task during the training process. The proposed approach can offer a real-time evaluation and discrimination of retinal pathologies with a depth-encoded OCT-A projected image. Our results show great accuracy of transfer learning CNN model on the classification task with the limited dataset. The CNN model with the pre-trained weights has better performance in comparison with an SVM using HOG feature approach.

Polarization-sensitive optical coherence tomography (PS-OCT) provides intrinsic contrast related to tissue microstructure. In the past, PS-OCT has been successfully used for imaging the anterior eye of humans in a variety of pathologic conditions. Here, we present PS-OCT imaging of the anterior eye in mice. Spectral domain PS-OCT centered at a wavelength of 840 nm was performed in anaesthetized laboratory mice. Three dimensional data sets were acquired at a 70 kHz A-line rate. PS-OCT images displaying phase retardation, birefringent axis orientation and degree of polarization uniformity (DOPU) were computed. Similar to human anterior segments, depolarization was observed in the corneal stroma and in structures containing melanin pigments such as the iris and the ciliary body. Birefringence was detected in the sclera close to the limbus. Aside from depolarizing foci observed within structures affected by cataract, the lens appeared mostly polarization preserving. Increased birefringence was observed in a scarred cornea. Given the similarity of the polarization characteristics in the murine eye and the human eye, PS-OCT lends itself as an ideal candidate for non-invasive imaging in preclinical studies in mouse models of anterior segment pathology.

Current retinal segmentation algorithms are based on layer or layer-boundary delineation. Although it works well for cases without sever structural abnormality, its applicability to heavily damaged tissue is low. In this study, we demonstrate pixel-wise segmentation of retinal pigment epithelium (RPE) and choroidal stroma by using multiple contrasts obtained by Jones-matrix OCT (JM-OCT). The method can be applicable equally to normal and pathologic cases. A custom made posterior JM-OCT is used to obtain multi-contrast retinal images. A single scan of JM-OCT provides multiple images including scattering OCT, attenuation coefficient, birefringence, degree-of-polarization uniformity, and OCT angiography. The tissue segmentation is done by applying a threshold to a “feature” which is a synthesized from the multi-contrast images. For RPE segmentation, the feature is defined as the third order combination of the optical contrasts. Then, the pixel is classified as RPE if the feature is larger than a particular threshold value. For choroidal stromal segmentation, another feature is defined as a second order combination of the optical features. After segmenting the RPE and choroidal stroma, RPE thickness map, RPE elevation map, whole choroidal thickness map, choroidal stromal thickness map, and choroidal vessel/stromal ratio map are generated in a normal and a myopic CNV complicated with non-sunset Vogt-Koyanagi-Harada disease (VKH-mCNV) cases. The generated maps of VKH-mCNV case visualize the absence of RPE, thinner choroidal thickness than normal case, and CNVs.

We non-invasively evaluated choroidal melanin contents in human eyes with PS-OCT. We calculated the percentage area of low DOPU in the choroidal interstitial stroma for Vogt-Koyanagi- Harada disease with sunset glow fundus, without sunset glow fundus, control group and tessellated fundus with high myopia. The mean percentage area of low DOPU in the sunset group was significantly lower than the other groups. PS-OCT provides an in vivo objective evaluation of choroidal melanin loss in vivo human eyes.

Adaptive optics-enabled optical coherence tomography (AO-OCT) and scanning laser ophthalmoscopy (AO-SLO) devices can resolve retinal cones and rods in three dimensions. To evaluate the improved resolution of AO-OCT and AO-SLO, a phantom that mimics retinal anatomy at the cellular level is required. We used a two-photon polymerization approach to fabricate three-dimensional (3D) photoreceptor phantoms modeled on the central foveal cones. By using a femtosecond laser to selectively photocure precise locations within a liquid-based photoresist via two-photon absorption, we produced high-resolution phantoms with μm-level dimensions similar to true anatomy. In this work, we present two phantoms to evaluate the resolution limits of an AO imaging system: one that models only the outer segments of the photoreceptor cells at varying retinal eccentricities and another that contains anatomically relevant features of the full-length photoreceptor. With these phantoms we are able to quantitatively estimate transverse resolution of an AO system and produce images that are comparable to those found in the human retina.

Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) is a powerful tool for retinal imaging at a cellular level. In conventional AOSLO, a pinhole conjugate to the retinal plane is used to reject out-of-focus light. This pinhole enables resolution improvement compared to standard bright-field microscopy imaging; however, the maximum resolution improvement can only be achieved when the pinhole is very small compared to the system’s point spread function. Thus, in practice one must find a compromise between the system’s achievable resolution and light throughput, which dictates the signal-to-noise ratio (SNR). In retinal imaging SNR is of high importance since the amount of light is limited by safety regulations. We introduce a new detection scheme into AOSLO using a similar technique to that recently developed for confocal scanning microscopy. Here we replace the single element pinhole detector with a multi-element design. This multi-element detector consists of a multimode fiber bundle with seven fibers, where the fiber tips are arranged in a closely-spaced hexagonal pattern on one side and are completely separated on the other side and each fiber is attached to a detector. Each of the fibers acts as a pinhole recording an image which is shifted with respect to the center fiber’s image. By aligning the images of the individual fibers and consolidating all of the light collected, an enhanced image with improved SNR can be processed. Thus, this design enables better SNR, without sacrificing resolution or altering imaging conditions. To demonstrate the capabilities of our system, we present phantom sample images.

Current-generation adaptive optics scanning laser ophthalmoscopes (AOSLO) are typically able to compensate for the optical aberrations of the human eye and achieve diffraction-limited illumination over a wide vergence range. However, to maximize the light collection efficiency of such a system, it is also necessary to have a collection path that is diffraction-limited for each imaging channel. Although it is trivial to achieve a high collection efficiency for a single channel AOSLO or a multi-channel AOSLO with minimal vergence differences between channels, for larger vergence differences, a careful consideration of the collection optics and their position and orientation within the collection path is needed. We present a methodology and system design for achieving diffraction-limited performance in both the illumination and collection paths of a multi-color AOSLO. The system consists of three imaging channels spanning different wavelength ranges (543 ± 11 nm, 680 ± 11 nm, and 840 ± 6 nm, respectively) and one near-infrared wavefront sensing channel (940 ± 5 nm). The maximum vergence difference between channels (measured at the exit pupil of the system) is ~1.2 diopters to compensate for the chromatic focal shift of the human eye. Preliminary imaging results from a healthy human adult volunteer demonstrate the system’s ability to resolve the foveal cone mosaic in all three imaging channels.

Adaptive Optics (AO) retinal imaging is revealing microscopic structures of the eye in a non-invasive way. Due to anisoplanatism, conventional AO systems are efficient on small 1°x1° field of view (FoV). We present a lens-based AO scanning laser ophthalmoscope (SLO) set-up with 2 deformable mirrors (DM), providing high-resolution retinal imaging on a 4°x4° FoV, for an eye pupil diameter of 7 mm. The first DM is in a pupil plane and is driven using a Shack-Hartmann (SH). The second DM is conjugated to a plane located 0.7 mm in front of the retina, to correct for aberrations varying within the FoV. Its shape is optimized using sensorless AO technique. The performance of this set-up was characterized in-vivo by measuring the eyes of four healthy volunteers. The obtained image quality was satisfactory and uniform over the entire FoV. Foveal cones could be resolved and no image distortion was detected. Furthermore, a 10°x10° FoV image was acquired at the fovea of one volunteer, by stitching 9 images recorded at different eccentricities. Finally, different layers of the retina were imaged. In addition to the photoreceptors mosaic, small capillaries and nerve fibers were clearly identified. The presented AO-SLO instrument provides high-resolution images of the retina on a relatively large FoV in reasonable time. With 2 DMs, one SH and no guide star, the system stays quite simple. The imaging performance of the set-up was validated on 4 healthy volunteers and we are currently imaging patients with different eye diseases.

High-resolution adaptive optics (AO) imaging of retinal neurons in living eyes holds promise for improved diagnosis and better assessment of treatment outcomes for retinal diseases. By integrating different imaging modalities, such as scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT), AO has enabled microscopic views of different retinal neurons, including recently reported retinal ganglion cells. In this study, we present a novel design of a multimodal adaptive optics imaging system to investigate the microscopic structure of living human retina. The optical system was designed using Zemax ray tracing software. The system performance was evaluated in terms of image quality and beam displacement. Optical performance was predicted to achieve diffraction limited image quality at the retinal plane and beam displacement was predicted to be >7× smaller than the pitch of Shack-Hartmann lenslet at the pupil planes for scan angles over 3.6°×3.6° field of view. The initial human subject images are presented. High quality photoreceptor images were acquired in both AO-SLO channel and AO-OCT channel simultaneously at 3° temporal from the fovea. Individual cones are delineated in AO-SLO image, the corresponding AO-OCT image showed four main reflections from outer retina, namely external limiting membrane, cone inner segment/outer segment junction, cone outer segment tip, and retinal pigment epithelium. The system allows flexibly alternating between AO-SLO and AO-OCT modes, which provides complementary views of retinal cells, and the potential to improve disease diagnosis and treatment.

Wet age-related macular degeneration (AMD) is a leading cause of vision loss in the United States. Choroidal neovascularization (CNV), the creation of new blood vessels in the choroid layer of the eye, plays a central role in the pathophysiology of wAMD. Despite advanced anti-VEGF therapy, 20% of patients become legally blind and other 30% suffer significant vision loss after 5 years. Given the significant burden imposed by wAMD on a growing aging population, there is an urgent need for developing new therapeutic techniques to remove microvessels induced by CNV. We developed a safe, noninvasive imaging-guided photo-mediated ultrasound therapy (PUT) technique as a localized antivascular method, and applied it to remove microvessels in the rabbit choroid. This technique promotes cavitation activity in blood vessels by concurrently applying ultrasound bursts and nanosecond laser pulses. The collapse of cavitation can induce damage to blood vessel endothelial cells, resulting in occlusion of microvessels. PUT takes advantages of the high native optical contrast among biological tissues, and has the unique capability to self-target microvessels without causing surrounding damages. Under the guidance of a fundus camera and an optical coherence tomography (OCT) system, our PUT system now has the capability to precisely target the treating area before the treatment procedure (through the fundus camera), and real-time intra-treatment cavitation monitor to evaluate the therapeutic effect (through the OCT system). Additionally, the safety of PUT technique is confirmed by histopathological studies.

Several methods have been proposed to assess changes in corneal biomechanical properties due to various factors, such as degenerative diseases, intraocular pressure, and therapeutic interventions (e.g. corneal collagen crosslinking). However, the effect of the corneal tissue hydration state on corneal stiffness is not well understood. In this work, we induce low amplitude (< 10 μm) elastic waves with a focused micro air-pulse in fresh in situ rabbit corneas (n = 10) in the whole eye-globe configuration at an artificially controlled intraocular pressure. The waves were then detected with a phase-stabilized swept source optical coherence elastography system. Baseline measurements were taken every 20 minutes for an hour while the corneas were hydrated with 1X PBS. After the measurement at 60 minutes, a 20% dextran solution was topically instilled to dehydrate the corneas. The measurements were repeated every 20 minutes again for an hour. The results showed that the elastic wave velocity decreased as the corneal thickness decreased. Finite element modeling (FEM) was performed using the corneal geometry and elastic wave propagation speed to assess the stiffness of the samples. The results show that the stiffness increased from ~430 kPa during hydration with PBS to ~500 kPa after dehydration with dextran, demonstrating that corneal hydration state, apart from geometry and intraocular pressure, can change the stiffness of the cornea.

Corneal collagen crosslinking (CXL) is a treatment used for corneal ectasia, a major cause of impaired vision in the United States and a leading indication for corneal transplantation. Existing methods of measuring the mechanical properties of normal and ectatic corneas still face a number of hurdles, including low spatial resolution, patient motion, measurement speed, patient comfort, and intraocular-pressure dependence. We have recently developed a phase-decorrelation OCT (PhD-OCT) method which avoids these drawbacks. PhD-OCT is sensitive to the endogenous random motion within the cornea. This nanometer-level motion can be detected with 5ms (M-scan) measurements using spectral-domain OCT. The random motion is reduced in crosslinked regions of the cornea, which provides contrast to enable mapping of corneal properties during CXL. These maps agree well with the current understanding of the CXL process, showing a distinct region of increased stiffness in the anterior portion of the cornea which corresponds to the demarcation line sometimes visible in conventional OCT. The PhD-OCT method uses conventional OCT and does not involve perturbing the cornea. This method may be useful clinically for pre-surgical screening, ectasia diagnosis, and treatment monitoring and customization.

Selective retina therapy (SRT) is an ophthalmological laser technique, targeting the retinal pigment epithelium (RPE) with repetitive microsecond laser pulses, while causing no thermal damage to the neural retina, the photoreceptors as well as the choroid. The RPE cells get damaged mechanically by microbubbles originating, at the intracellular melanosomes. Beneficial effects of SRT on Central Serous Retinopathy (CSR) and Diabetic Macula Edema (DME) have already been shown. Variations in the transmission of the anterior eye media and pigmentation variation of RPE yield in intra- and inter- individual thresholds of the pulse energy required for selective RPE damage. Those selective RPE lesions are not visible. Thus, dosimetry-systems, designed to detect microbubbles as an indicator for RPE cell damage, are demanded elements to facilitate SRT application. Therefore, a technique based on the evaluation of backscattered treatment light has been developed. Data of 127 spots, acquired during 10 clinical treatments of CSR patients, were assigned to a RPE cell damage class, validated by fluorescence angiography (FLA). An algorithm has been designed to match the FLA based information. A sensitivity of 0.9 with a specificity close to 1 is achieved. The data can be processed within microseconds. Thus, the process can be implemented in existing SRT lasers with an automatic pulse wise increasing energy and an automatic irradiation ceasing ability to enable automated treatment close above threshold to prevent adverse effects caused by too high pulse energy. Alternatively, a guidance procedure, informing the treating clinician about the adequacy of the actual settings, is possible.

Degenerative conditions such as keratoconus and Fuch’s dystrophy can alter over time the cellular structure of the human corneal epithelium and endothelium respectively. A high-speed UHR-OCT system, capable of generating volumetric images of the cellular structure of the human cornea was built. The UHR-OCT system has a compact fiber-optic design that utilizes a commercial femtolaser with the central wavelength of 790 nm and 3dB spectral bandwidth of 150 nm to achieve ~ 1.4 µm axial resolution in corneal tissue. The optical design of the OCT imaging probe ensured ~2 µm OCT lateral resolution in corneal tissue. At the detection end of the UHR-OCT system, a high-resolution spectrometer (Cobra, Wasatch Photonics) is interfaced with a novel line scan camera. The camera has a tall pixel design, 2048 pixel array and a maximum readout rate of 250 kHz. The system’s SNR was 96 dB at 100 µm away from the zero delay line, with a 10 dB roll-off over 1.5 mm scanning range for ~800 µm power of the imaging beam incident on the corneal surface. Volumetric images of healthy and pathological corneas were acquired in-vivo from healthy volunteers and subjects with keratoconus and Fuch’s dystrophy and the images were compared with typical histological images. This study was approved by the University of Waterloo Research Ethics Committee.

Limbal stem cell dysfunction (LSCD) causes morphological and physiological changes in the limbus that result in decreased vision, photophobia, tearing, chronic inflammation and hyperemia, recurrent episodes of pain, and blindness in severe cases. Currently, clinical in-vivo imaging of the palisaded of Vogt (POV) and the cellular structure of the limbal crypts in the human corneo-scleral limbus is accomplished by in-vivo confocal microscopy (IVCM). However, IVCM requires physical contact with the limbal tissue that can cause pain and inflammation. In this study, we used a novel high speed, ultra-high resolution optical coherence tomography (UHR-OCT) system to generate volumetric, cellular resolution image of the healthy and pathological human corneo-scleral limbus. The UHR-OCT system has a compact fiber-optic design. A femtosecond laser with 790 nm central wavelength and ~150 nm spectral bandwidth (at 3dB) was used to achieve ~1.4 µm axial resolution in biological tissue. The UHR-OCT system also utilizes a high resolution spectrometer (Cobra, Wasatch Photonics) connected to a novel line scan camera with a tall pixel design, 2048 pixel array and a maximum readout rate of 250 kHz. The system’s SNR was 96 dB at 100 µm away from the zero delay line, with ~10 dB roll-off over 1.5 mm scanning range for ~800 µm power of the imaging beam. Volumetric images of the POV and the cellular structure of the limbal crypts were acquired in-vivo and without contact with the limbal tissue from healthy and LSCD and subjects. This study was approved by the University of Waterloo Research Ethics Committee.

Despite obvious improvements in visualization of the in vivo cornea through the faster imaging speeds and higher axial resolutions, cellular imaging stays unresolvable task for OCT, as en face viewing with a high lateral resolution is required. The latter is possible with FFOCT, a method that relies on a camera, moderate numerical aperture (NA) objectives and an incoherent light source to provide en face images with a micrometer-level resolution. Recently, we for the first time demonstrated the ability of FFOCT to capture images from the in vivo human cornea1. In the current paper we present an extensive study of appearance of healthy in vivo human corneas under FFOCT examination. En face corneal images with a micrometer-level resolution were obtained from the three healthy subjects. For each subject it was possible to acquire images through the entire corneal depth and visualize the epithelium structures, Bowman’s layer, sub-basal nerve plexus (SNP) fibers, anterior, middle and posterior stroma, endothelial cells with nuclei. Dimensions and densities of the structures visible with FFOCT, are in agreement with those seen by other cornea imaging methods. Cellular-level details in the images obtained together with the relatively large field-of-view (FOV) and contactless way of imaging make this device a promising candidate for becoming a new tool in ophthalmological diagnostics.

Full-Field Optical Coherence Tomography (FF-OCT) reveals submicrometric morphological details in retinal explants without the use of contrast agents. Dynamic FF-OCT (D-FF-OCT) takes advantage of the temporal evolution of the local FF-OCT signal to reveal a movement-dependent contrast inside tissues, mostly relying on cellular motility. Compared to regular FF-OCT images, the relative contrast from stationary structures such as nerve fibers is reduced, and contrast inside cells is enhanced, revealing many more cells, as well as the position of nuclei, and cell metabolism. We used a multimodal FF-OCT, D-FF-OCT and fluorescence microscope to compare and identify the structures observed in D-FF-OCT, which allowed us to reconstruct the full 3-D micrometric organization of corneal and retinal explants. In healthy explants, this multimodal association allows the label-free specific detection of all cell populations, except from the Mueller cells, and of several structural features such as nerve and collagen fibers, and pedicles and spherules. D-FF-OCT also accesses several functional contrasts (relying on metabolism, mechanical and electrical activity) that can be combined to monitor the tissue health over time. It is anticipated that such a combination of static and dynamic OCT information may be used in vivo in future for the early detection of ocular pathologies. To this end, we tried here to foster our understanding of the progression and occurrence of such diseases in animal models. We notably used this optical system to follow the evolution of stem cells injected in the cornea and to assess the concentration of macrophages in retinas with inflammation.

The inner retina is critical for visual processing, but much remains unknown about its neural circuitry and vulnerability to disease. A major bottleneck has been our inability to observe the structure and function of the cells composing these retinal layers in the living human eye. Here, we present a noninvasive method to observe both structural and functional information. Adaptive optics optical coherence tomography (AO-OCT) is used to resolve the inner retinal cells in all three dimensions and novel post processing algorithms are applied to extract structure and physiology down to the cellular level. AO-OCT captured the 3D mosaic of individual ganglion cell somas, retinal nerve fiber bundles of micron caliber, and microglial cells, all in exquisite detail. Time correlation analysis of the AO-OCT videos revealed notable temporal differences between the principal layers of the inner retina. The GC layer was more dynamic than the nerve fiber and inner plexiform layers. At the cellular level, we applied a customized correlation method to individual GCL somas, and found a mean time constant of activity of 0.57 s and spread of ±0.1 s suggesting a range of physiological dynamics even in the same cell type. Extending our method to slower dynamics (from minutes to one year), time-lapse imaging and temporal speckle contrast revealed appendage and soma motion of resting microglial cells at the retinal surface.

Full-field-swept-source optical coherence tomography is capable of detecting small morphological changes in the living human eye below sub-wavelength range by evaluating the phases. This is used to obtain intrinsic optical signals originating in the photoreceptor outer segment, spatially resolved to single photoreceptors. These were measured ex-vivo in explanted porcine retina as well as in the living human eye. The obtained signals are related to an increase of the optical path length of the outer segments. However, they give no hint wether they are caused by an actual physical expansion of the outer segments or by a changes in the index of refraction. Therefore, systematical measurements were carried out to determine the physical nature and biochemical source of the observed effects.

Optical coherence tomography (OCT) is a standard for retinal imaging and has been integrated to surgical microscopes to evaluate tissue-instrument interactions during macular surgery. One common procedure during such surgery, membrane peeling, is done under a white light microscope. Indocyanine green (ICG) can be used to specifically dye the inner limiting membrane (ILM) and facilitates this surgery. However, there is no equivalent contrast mechanism to specifically target the ILM on OCT images. We propose to use photothermal OCT (PT-OCT) to detect ICG in the OCT field-of-view, which would increase contrast between the ILM and other structures of the retina. As preliminary data for this project, we have collected PT-OCT images of different ICG phantoms over a wide range of laser powers and ICG concentrations, including concentrations lower than the clinical standard. We have also detected a PT-OCT signal from ICG on a mouse tail with low photothermal laser powers (0.56 mW) to evaluate the feasibility of this technique for in vivo ocular imaging. Finally, we have collected PT-OCT images of a fixed monkey retina after the ILM was dyed with ICG, and obtained a PT-OCT signal from the ICG and the melanin present in the retinal pigment epithelium and the choroid. Those preliminary results indicate that ICG can be detected with PT-OCT at low concentrations and low laser powers. PT-OCT has never been demonstrated in the human eye and has only been recently demonstrated in the mouse eye. This experiment establishes feasibility for PT-OCT in clinical applications.

There is great clinical importance in identifying cellular responses in the anterior chamber (AC) which can indicate signs of hyphema (an accumulation of red blood cells (RBCs)) or aberrant intraocular inflammation (an accumulation of white blood cells (WBCs)). These responses are difficult to diagnose and require specialized equipment such as ophthalmic microscopes and specialists trained in examining the eye. In this work, we applied spectroscopic OCT to differentiate between RBCs and subtypes of WBCs, including neutrophils, lymphocytes and monocytes, both in vitro and in ACs of porcine eyes. We located and tracked single cells in OCT volumetric images, and extracted the spectroscopic data of each cell from the detected interferograms using short-time Fourier Transform (STFT). A look-up table of Mie spectra was generated and used to correlate the spectroscopic data of single cells to their characteristic sizes. The accuracy of the method was first validated on 10um polystyrene microspheres. For RBCs and subtypes of WBCs, the extracted size distributions based on the best Mie spectra fit were significantly different between each cell type by using the Wilcoxon rank-sum test. A similar size distribution of neutrophils was also acquired in the measurements of cells introduced into the ACs of porcine eyes, further supporting spectroscopic OCT for potentially differentiating and quantifying blood cell types in the AC in vivo.

Transparency of the ocular structures affect the contrast in the retinal image and has an impact on final visual quality. Although opacities are mostly formed in the crystalline lens of aging eye (cataract formation), visual function can be also altered by the opacities in the vitreous body. We demonstrate three-dimensional (3-D) visualization of vitreous opacities in vivo. We developed a prototype long-depth-range Swept-Source OCT instrument operating at the speed of 50 kA-scans/second and at the central wavelength of 1 μm to perform high-resolution imaging of the whole anterior segment of the eye or the retina. Different configurations of the interface with focus-tunable optics have been developed to optimize vitreous imaging. Volumetric data sets of eyes with vitreous opacities were acquired and processed to obtain contrast-enhanced high-resolution images. Vitreous surface segmentation enabled generation of 3-D rendering and en-face views of vitreous opacities in its anterior and posterior interfaces. The results demonstrate the ability of the OCT imaging to characterize the opacities. In conclusion, 3-D long-depth-range SS-OCT enables volumetric visualization of in vivo microstructural changes in the vitreous related to opacification. The instrument might be a useful tool in the high-resolution evaluation and surgical management of vitreous opacities.

The present study aimed to elucidate the angular distribution of the Pigment epithelium central limit-Inner limit of the retina Minimal Distance measured over 2π radians in the frontal plane (PIMD-2π) in young healthy eyes. Both healthy eyes of 16 subjects aged [20;30[ years were included. In each eye, a volume of the optical nerve head (ONH) was captured three times with a TOPCON DRI OCT Triton (Japan). Each volume renders a representation of the ONH 2.8 mm along the sagittal axis resolved in 993 steps, 6 mm long the frontal axis resolved in 512 steps and 6 x mm along the longitudinal axis resolved in 256 steps. The captured volumes were transferred to a custom made software for semiautomatic segmentation of PIMD around the circumference of the ONH. The phases of iterated volumes were calibrated with cross correlation. It was found that PIMD-2π expresses a double hump with a small maximum superiorly, a larger maximum inferiorly, and minima in between. The measurements indicated that there is no difference of PIMD-2π between genders nor between dominant and not dominant eye within subject. The variation between eyes within subject is of the same order as the variation among subjects. The variation among volumes within eye is substantially lower.

In conventional fundus photography, illuminating light is delivered to the interior of the eye through the pupil. To avoid reflection from cornea and crystalline lens, peripheral area of the pupil is used for delivering illumination light and only the central part of the pupil can be used for collecting imaging light. Therefore, the optical design of conventional fundus cameras is sophisticated, the field of view is limited, and pupil dilation is required for evaluating the retinal periphery which is frequently affected by diabetic retinopathy (DR), retinopathy of premature (ROP), and other chorioretinal conditions. Trans-scleral illumination has been proposed as one alternative illumination method to achieve wide field fundus examination not requiring pharmacologic pupil dilation. However, clinical deployment of trans-scleral illumination failed due to the contact mode illumination and imaging, and complication of instrument operation. Here we report a nonmydriatic wide field fundus camera employing trans-pars-planar illumination which delivers illuminating light through the pars plana, an area outside of the pupil without contacting the eye. Trans-pars-planar illumination frees the entire pupil for imaging purpose only, and thus wide field fundus photography can be readily achieved with less pupil dilation. For proof-of-concept testing, using all off-the-shelf components a prototype instrument that can achieve 90° fundus view coverage in single-shot fundus images, without the need of pharmacologic pupil dilation was demonstrated.

OCT is the gold standard for clinical diagnosis and treatment of many retinal diseases. Most clinical OCT systems are table top systems that can only image seated, compliant patients that can fixate. These systems are incapable of imaging several important patient populations including bedridden patients and infants. In this work we describe the use of a custom, light weight, handheld OCT probe based on a high speed swept source engine for imaging in the intensive care nursery. The probe uses custom optics, optomechanics, and a MEMS mirror to achieve a weight of only 211g. The portability and imaging speed of this probe facilitates repeat, volumetric, bedside imaging in a challenging imaging environment. To date we have imaged over 43 pre-term and full-term infants in the intensive care nursery, with some patients having up to 15 imaging sessions starting at 30 weeks post menstrual age. Volumetric OCT enables visualization of the complex 3D structures associated with retinal pathology that is unavailable to slower, B-scan based probes. Repeat imaging shows the development of both normal and diseased retinal structures. We believe that OCT imaging of these infants will reveal retinal abnormalities, enable further study of pediatric retinal diseases, and allow for better management and prediction of future visual outcomes.

Elevated intracranial pressure (ICP) can result from a variety of etiologies including severe head trauma, brain tumors and inflammations, or spontaneously (idiopathic). Sustained elevated ICP can be damaging to the central nervous system and potentially fatal depending on the magnitude and rate of pressure elevation. A classic ophthalmic sign of elevated ICP is optic disc edema or papilledema. A previous study has shown that magnetic resonance imaging (MRI) can visualize posterior eye flattening in the presence of increased ICP. In contrast to MRI, optical coherence tomography (OCT) is a more commonly used and available ocular imaging technique that can readily show swelling of the optic nerve head relative to the surrounding retinal surface. However, the ability to recover an accurate estimate of retinal radius of curvature (Rc) requires several other parameters such as the ocular axial length and distance from the imaging system. To address this need, we developed a custom whole eye OCT system (centered at 1050nm; 100kHz A-scan rate) providing simultaneous wide field of views of the anterior and posterior ocular segments. A subject was seen in the Duke neuro-ophthalmology clinic with papilledema from idiopathic intracranial hypertension (IIH). They were imaged with MRI as part of their clinical workup. Retinal Rc as measured by both OCT and MRI were comparable and indicated posterior flattening of the globe compared to normal.

The biomechanical properties of the sclera could provide key information regarding the progression and etiology of ocular diseases. For example, an elevated intraocular pressure is one of the most common risk factors for glaucoma and can cause pathological deformations in the tissues of the posterior eye, such as the sclera, potentially damaging these vital tissues. Previous work has evaluated scleral biomechanical response to global displacements with techniques such as inflation testing. However, these methods cannot provide localized biomechanical assessments. In this pilot work, we induce low amplitude (< 10 μm) elastic waves using acoustic radiation force in posterior scleral tissue of fresh porcine eyes (n=2) in situ. The wave propagation induced using an ultrasound transducer was detected across an 8 mm region using a phase-sensitive optical coherence elastography system (PhS-OCE). The elastographic measurements were taken at various artificially controlled intraocular pressures (IOP). The IOP was pre-cycled before being set to 10 mmHg for the first measurement. Subsequent measurements were taken at 20 mmHg and 30 mmHg for each sample. The results show an increase in the stiffness of the sclera as a function of IOP. Furthermore, we observed a variation in the elasticity based on direction, suggesting that the sclera has anisotropic biomechanical properties. Our results show that OCE is an effective method for evaluating the mechanical properties of the sclera, and reveals a new area for our future work.

Purpose: To objectively quantify dynamic changes in lens shape during accommodation using two-dimensional OCT images Methods: In-vivo responses to an accommodative step stimulus of three subjects (aged 22, 39, and 45) were captured using a custom-made extended-depth SD-OCT system operating at 840 nm following an IRB-approved protocol (Ruggeri et al. 2012). Subjects focused on a visual accommodation target designed to produce an adjustable step stimulus of accommodation. Accommodative responses to 2-D and 4-D stimuli were captured ~1.5s before and ~4.5s after stimulation. Lens thickness, anterior curvature, and posterior curvature were measured using a newly-developed algorithm (validated using a calibration sphere). Dynamic changes in lens thickness and curvature were then fitted with an exponential model to produce time dependent constants. Results: All calibration OCT images were automatically analyzed in under 2 seconds. A radius of 7.793mm ± 0.051mm was calculated resulting in a difference of 2.4μm from the reported nominal value of the calibration sphere. Anterior lens radius decreased over time in all subjects. Radius of the posterior lens experienced a slight increase for all subjects. Conclusion: This study demonstrates the feasibility of quantifying the dynamic changes in lens curvature and thickness during accommodation using extended-depth OCT combined with a step accommodation stimulus and an automated segmentation algorithm.

We present a new adaptive optics visual simulator (AOVS), allowing to both measure and manipulate the optical aberrations of the eye of any patient, including those with large refractive errors. The instrument incorporates a Hartmann-Shack wavefront sensor (HS), a liquid crystal on silicon spatial light modulator (LCOS-SLM), and a variable lens. A motorized diaphragm with a variable diameter ranging from 0.5 to 8.2 mm was incorporated at the exit pupil plane of the instrument, permitting visual testing for any pupil size. Presenting of visual stimuli was done using a high definition digital light processing projector (DLP), which provided provided bright, realistic visual conditions, enabling photopic vision. The AO visual simulator has been successfully proved in real subjects, including those exhibiting moderate and high levels of myopia. The AOVS was successfully tested in different subjects, including those exhibiting moderate and high levels of myopia. Aberrations were measured with the HS after pre-compensation of defocus with the variable lens, and LCOS-SLM corrected for the rest of aberrations. This visual simulator could be used in most patients, irrespectively of their refraction or the amount of aberrations.

Intra-Tissue Refractive Index Shaping (IRIS) uses a 405 nm femtosecond laser focused into the stromal region of the cornea to induce a local refractive index change through multiphoton absorption. This refractive index change can be tailored through scanning of the focal region and variations in laser power to create refractive structures, such as gradient index lenses for visual refractive correction. Previously, IRIS was used to create 2.5 mm wide, square, -1 D cylindrical refractive structures in living cats. In the present work, we first wrote 400 μm wide bars of refractive index change at varying powers in enucleated cat globes using a custom flexure-based scanning system. The cornea and surrounding sclera were then removed and mounted into a wet cell. The induced optical phase change was measured with a Mach- Zehnder Interferometer (MZI), and appeared as fringe displacement, whose magnitude was proportional to the refractive index change. The interferograms produced by the MZI were analyzed with a Fourier Transform based algorithm in order to extract the phase change. This provided a phase change versus laser power calibration, which was then used to design the scanning and laser power distribution required to create -1.5 D cylindrical Fresnel lenses in cat cornea covering an area 6 mm in diameter. This prescription was inscribed into the corneas of one eye each of two living cats, under surgical anesthesia. It was then verified in vivo by contrasting wavefront aberration measurements collected pre- IRIS with those obtained over six months post-IRIS using a Shack-Hartmann wavefront sensor.

The presented eye tracking-based system for measuring strabismus angle, aims to replace the standard manual “prism cover test (PCT)” procedure. PCT is performed by occluding one eye and observing the compensatory contralateral eye movement. Our innovative wavelength selective goggles enable accurate monitoring of both eyes constantly even during the occlusion of the eye, by blocking visible light while transmitting the IR light for the eye tracker. The test procedure detects and measures both manifest [heterotropia] and latent [heterophoria] strabismus, it also detects the deviating eye - right, left or alternating, This patent pending system is using a short video game and doesn’t require calibration and thus is suitable for all ages including infants and toddlers. The system alternately displays two moving monocular targets on a 45 cm. display until the line-of-sight of each eye coincides with its corresponding target as determined by the eye tracker. The efficacy of system was proven in a clinical study comparing the manual PCT results of two experienced examiners with repeated automatic test results. 31 adult subjects (26.8±4.6 y/o, mean±SD) were tested. The eye-tracking results were 13.7±1.54, compared to PCT results of 14.3±1.35 prism diopters (mean±SE) - correlation of over 89%. The automatic test demonstrating was twice as repeatable as the conventional measurement (P<0.005 paired t-test). The duration of the test was under 30 sec. These results indicate the feasibility of accurate and repeatable measurements of strabismus angles by the automatic objective system which can be used for screening, diagnosis and monitoring of strabismus and heterophoria.

Most reported photoacoustic ocular imaging work to date uses small animals, such as mice and rats, the eyes of which are small and less than one-third the size of a human eye, which poses a challenge for clinical translation. Here we achieved chorioretinal imaging of larger animals, i.e. rabbits, using a dual-modality photoacoustic microscopy (PAM) and optical coherence tomography (OCT) system. Preliminary experimental results in living rabbits demonstrate that the PAM can noninvasively visualize depth-resolved retinal and choroidal vessels using a safe laser exposure dose; and the OCT can finely distinguish different retinal layers, the choroid, and the sclera. This reported work might be a major step forward in clinical translation of photoacoustic microscopy.

Purpose: To investigate the feasibility of using spectral domain optical coherence tomography (SD-OCT), infra-red and multicolor fundus imaging for monitoring the safety and efficacy of therapeutics delivery into the extravascular spaces of the choroid (EVSC). Methods: Two hundred and fifty microliters containing Indocyanine Green (ICG), sodium fluorescein, iron oxide nanoparticles (IONPs) or 15 million human bone marrow stromal cells (hBMSCs) were injected using a novel minimally-invasive adjustable-depth blunt injector into the EVSC of New Zealand White rabbits, 3.5 mm posterior to the limbus. SD-OCT, infra-red and multicolor fundus imaging and histology analysis were performed to assess injection safety and efficacy. Results: Infra-red wide angle (102°) imaging demonstrated that injected therapeutics covered over 80% of the posterior eye surface across the EVSC. Multicolor imaging demonstrated that injected dyes were localized in the matrix between the choroidal blood vessels. SD-OCT analysis revealed no retinal detachment, choroidal hemorrhages or inflammation up to 10 week following cell transplantation. These findings were supported by histology analysis. Conclusions: Multimodal imaging including infra-red and multicolor fundus imaging as well as SD-OCT enables longitudinal monitoring of safety and efficacy of therapeutics delivery into the EVSC. Moreover, these imaging techniques enable to quantitatively determine the distribution of injected therapeutics in the EVSC.

Rodent models are robust tools for understanding human retinal disease and function because of their similarities with human physiology and anatomy and availability of genetic mutants. Optical coherence tomography (OCT) has been well-established for ophthalmic imaging in rodents and enables depth-resolved visualization of structures and image-based surrogate biomarkers of disease. Similarly, fluorescence confocal scanning laser ophthalmoscopy (cSLO) has demonstrated utility for imaging endogenous and exogenous fluorescence and scattering contrast in the mouse retina. Complementary volumetric scattering and en face fluorescence contrast from OCT and cSLO, respectively, enables cellular-resolution longitudinal imaging of changes in ophthalmic structure and function. We present a non-contact multimodal OCT+cSLO small animal imaging system with extended working distance to the pupil, which enables imaging during and after intraocular injection. While injections are routinely performed in mice to develop novel models of ophthalmic diseases and screen novel therapeutics, the location and volume delivered is not precisely controlled and difficult to reproduce. Animals were imaged using a custom-built OCT engine and scan-head combined with a modified commercial cSLO scan-head. Post-injection imaging showed structural changes associated with retinal puncture, including the injection track, a retinal elevation, and detachment of the posterior hyaloid. When combined with imagesegmentation, we believe OCT can be used to precisely identify injection locations and quantify injection volumes. Fluorescence cSLO can provide complementary contrast for either fluorescently labeled compounds or transgenic cells for improved specificity. Our non-contact OCT+cSLO system is uniquely-suited for concurrent imaging with intraocular injections, which may be used for real-time image-guided injections.

The presence and characteristics of drusen in retinal images, namely their size, location, and distribution, can be used to aid in the diagnosis and monitoring of Age Related Macular Degeneration (AMD); one of the leading causes for blindness in the elderly population. Current imaging techniques are effective at determining the presence and number of drusen, but fail when it comes to classifying their size and form. These distinctions are important for correctly characterising the disease, especially in the early stages where the development of just one larger drusen can indicate progression. Another challenge for automated detection is in distinguishing them from other retinal features, such as cotton wool spots. We describe the development of a multi-spectral scanning-laser ophthalmoscope that records images of retinal autofluorescence (AF) in four spectral bands. This will offer the potential to detect drusen with improved contrast based on spectral discrimination for automated classification. The resulting improved specificity and sensitivity for their detection offers more reliable characterisation of AMD. We present proof of principle images prior to further system optimisation and clinical trials for assessment of enhanced detection of drusen.

The illumination of the intraocular space during pars plana vitrectomy always bears the risk of retina damage by irradiation. Conventional illumination systems consist of an external light source and an optical fiber to transfer the visible light (radiation) into the eye. Often xenon arc and halogen lamps are employed for this application with some disadvantageous properties like high phototoxicity and low efficiency. Therefore, we propose to generate the light directly within the eye by inserting a white micro LED with a diameter of 0.6 mm. The LED offers a luminous flux of 0.6 lm of white light with a blue peak @ 450 nm and a yellow peak @ 555 nm. The presented prototypes fit through a standard 23 G trocar and are the first intraocular light sources worldwide. Two different single-use approaches have already been developed: a handguided and a chandelier device. The hand-guided applicator enables a directly navigation and illumination up to a working distance of 6 mm. The chandelier device is much smaller and does not need an active navigation of the light cone. The brightness and homogeneity of the illumination of these LED devices have been successfully tested on porcine eyes. Presented measurements and calculations prove that even for high LED currents and small distances to the retina these intraocular micro LED devices expose the retina to less hazard than conventional illumination sources like fiber based xenon systems. Even under the worst circumstances application durations of 180 hours would be justifiable.

The use of Raman spectroscopy in biochemistry has been very successful, particularly because of its ability to identify elementary chemical species. However, application of this spectroscopic technique for in vivo assessment is often limited by autofluorescence, which make detection of Raman signatures difficult. The mouse eye has been used as an optical testbed for investigation of a variety of disease models and therapeutic pathways. Implementation of in vivo Raman spectroscopy in mice retina would be valuable but needs to be examined in context of the intrinsic auto-fluorescence artifact and potential light damage if high probing beam powers were used. To evaluate feasibility, a Raman system was built on a custom SLO/OCT platform allowing mouse positioning and morphological data acquisition along with the Raman signal from a desired retinal eccentricity. The performance of the Raman system was first assessed with a model eye consisting of polystyrene in the image plane (retina), using excitation wavelengths of 488 nm, 561 nm, and 785 nm to determine whether auto-fluorescence would be reduced at longer wavelengths. To improve the SNR, the combined system is featured with the optical compatibility for these three excitations such that their corresponding spectra from a typical region of interest can be acquired consecutively during single imaging run. Our results include emission spectra acquired over 10 s with excitation energy less than 160 J^.s^-1.m^-2 for all wavelengths and corresponding retinal morphology for different mouse strains including WT, BALB/c and ABCA4^-/-.

A visual just noticeable difference (VJND) is the amount of change in either an image (e.g. a photographic print) or in vision (e.g. due to a change in refractive power of a vision correction device or visually coupled optical system) that is just noticeable when compared with the prior state. Numerous theoretical and clinical studies have been performed to determine the amount of change in various visual inputs (power, spherical aberration, astigmatism, etc.) that result in a just noticeable visual change. Each of these approaches, in defining a VJND, relies on the comparison of two visual stimuli. The first stimulus is the nominal or baseline state and the second is the perturbed state that results in a VJND. Using this commonality, we converted each result to the change in the area of the modulation transfer function (AMTF) to provide a more fundamental understanding of what results in a VJND. We performed an analysis of the wavefront criteria from basic optics, the image quality metrics, and clinical studies testing various visual inputs, showing that fractional changes in AMTF resulting in one VJND range from 0.025 to 0.075. In addition, cycloplegia appears to desensitize the human visual system so that a much larger change in the retinal image is required to give a VJND. This finding may be of great import for clinical vision tests. Finally, we present applications of the VJND model for the determination of threshold ocular aberrations and manufacturing tolerances of visually coupled optical systems.

In previous studies conducted in our lab, we have been investigating the aging effects on sunglasses. Some preliminary results have been indicating changes on the UV protection on the lenses. Therefore, besides irradiating the samples with a proper sun simulator, we have also been concerned on exposing the sunglasses to natural sun for further investigation and comparisons. Thus, this project aims expose the lenses for 24 months using an automatic solar exposition station, which consists of a series of 5 panels, housing 60 lenses arranged in the vertical position to the ground, which will be irradiated by the sun from sunrise until sunset. A box structure moves along a rail, driven by a motor and then the lenses are exposed. Humidity, rain, temperature, dust and UV index sensors, as well as a video camera are part of the system. The exposure time and UV index will be recorded and automatic opening or closing the box system may also be controlled by a PC using a webserver. The system was tested in working conditions, i.e. exposed to the weather and being automatically controlled, for five months to certifying that the samples could be exposed without being damaged. The next step of the research is to start the exposition cycles and to measure the expected transmittance variations after each cycle.

Ultraviolet radiation (UVR) is the part of radiation emitted by the Sun, with range between 280 nm and 400 nm, and that reaches the Earth’s surface. The UV rays are essential to the human because it stimulates the production of vitamin D but this radiation may be related to several health problems, including skin cancer and ocular diseases like pterygium, photokeratitis, cataract and more. To inform people about UV radiation, it is adopted the Ultraviolet Index (UVI). This UVI consists in a measure of solar UV radiation level, which contributes to cause sunburn on skin, also known as Erythema, and is indicated as an integer number between 1 and 14, associated to categories from low to extreme respectively. The aim of this work was to develop a low cost UVI datalogger capable of measuring three different UVI sensors simultaneously, record their data with timestamp and serve the measures online through a dedicated server, so general public can access their data and see the current UV radiation conditions. We also compared three different UVI sensors (SGlux UV cosine, Skye SKU440 and SiLabs SI1145) between them and with meteorological models during a period of months to verify their compliance. With five months data, we could verify the sensors working characteristics and decide which among them are the most suitable for research purposes.

We demonstrated the feasibility of using holographic waveguide for eye tracking. A custom-built holographic waveguide, a 20 mm x 60 mm x 3 mm flat glass substrate with integrated in- and out-couplers, was used for the prototype development. The in- and out-couplers, photopolymer films with holographic fringes, induced total internal reflection in the glass substrate. Diffractive optical elements were integrated into the in-coupler to serve as an optical collimator. The waveguide captured images of the anterior segment of the eye right in front of it and guided the images to a processing unit distant from the eye. The vector connecting the pupil center (PC) and the corneal reflex (CR) of the eye was used to compute eye position in the socket. An eye model, made of a high quality prosthetic eye, was used prototype validation. The benchtop prototype demonstrated a linear relationship between the angular eye position and the PC/CR vector over a range of 60 horizontal degrees and 30 vertical degrees at a resolution of 0.64-0.69 degrees/pixel by simple pixel count. The uncertainties of the measurements at different angular positions were within 1.2 pixels, which indicated that the prototype exhibited a high level of repeatability. These results confirmed that the holographic waveguide technology could be a feasible platform for developing a wearable eye tracker. Further development can lead to a compact, see-through eye tracker, which allows continuous monitoring of eye movement during real life tasks, and thus benefits diagnosis of oculomotor disorders.

This study presents a spectral domain optical coherence tomography (SD-OCT) using supercontinuum laser combined with a fundus photography for in vivo high-resolution imaging of retinal degeneration in Royal College of Surgeons (RCS-/- rat). These findings were compared with the Sprague-Dawley (SD) rats and the corresponding histology. Quantitative measurements show that changes in thickness were not significantly different between SD control and young RCS retinas (4 weeks). However, in old RCS rats (55 weeks), the thickness of photoreceptor layer decreased significantly as compared to young RCS rats (both 4 weeks and 5 weeks). After contrast enhancement method, this platform will be useful for the quantitative evaluation of the degree of retinal degeneration, treatment outcome after therapy, and drug screening development in the future.

Cataract is the most prevalent cause of visual impairment worldwide. Cataracts can be formed due to trauma, radiation, drug abuse, or low temperatures. Thus, early detection of cataract can be immensely helpful for preserving visual acuity by ensuring that the appropriate therapeutic procedures are performed at earlier stages of disease onset and progression. In this work, we utilized a phase-sensitive optical coherence elastography (OCE) system to quantify changes in biomechanical properties of porcine lenses in vitro with induced cold cataracts. The results show significant increase in lens Young’s modulus due to formation of the cold cataract (from ~ 35 kPa to ~60 kPa). These results show that OCE can assess lenticular biomechanical properties and may be useful for detecting and, potentially, characterizing cataracts.

A Telescope window is a novel concept of transformation-optics consisting of an array of micro-telescopes, in our configuration, of a Galilean type. When the array is considered as one multifaceted device, it acts as a traditional Galilean telescope with distinctive and attractive properties such as compactness and modularity. Each lenslet, can in principle, be independently designed for a specific optical function. In this paper, we report on the design, manufacture and prototyping, by diamond precision machining, of 2 concepts of telescope windows, and discuss both their performances and limitations with a view to use them as potential low vision aid devices to support patients with macular degeneration.

We examine the dioptric power and transmitted wavefront of a contact lens as it releases its handling stresses. Handling stresses are introduced as part of the contact lens loading process and are common across all contact lens measurement procedures and systems.

The latest advances in vision correction require tighter quality control during the manufacturing of the contact lenses. The optical power of contact lenses is one of the critical characteristics for users. Power measurements are conducted in the hydrated state, where the lens is resting inside a solution-filled glass cuvette. In a typical approach, the contact lens must be subject to long settling times prior to any measurements. Alternatively, multiple measurements must be averaged. Apart from potential operator dependency of such approach, it is extremely time-consuming, and therefore it precludes higher rates of testing.

Comprehensive knowledge about the settling process can be obtained by monitoring multiple parameters of the lens simultaneously. We have developed a system that combines co-aligned a Shack-Hartmann transmitted wavefront sensor and a time-domain low coherence interferometer to measure several optical and physical parameters (power, cylinder power, aberrations, center thickness, sagittal depth, and diameter) simultaneously. We monitor these parameters during the stress relaxation period and show correlations that can be used by manufacturers to devise methods for improved quality control procedures.

A novel compact optical biochip based on a thin layer-sensing BICELL surface of nitrocellulose is used for in-situ labelfree detection of dry eye disease (DED). In this work the development of a compact biosensor that allows obtaining quantitative diagnosis with a limited volume of sample is reported. The designed sensors can be analyzed with an optical integrated Point-of-Care read-out system based on the “Increase Relative Optical Power” principle which enhances the performance and Limit of Detection. Several proteins involved with dry eye dysfunction have been validated as biomarkers. Presented biochip analyzes three of those biomarkers: MMP9, S100A6 and CST4. BICELLs based on nitrocellulose permit to immobilize antibodies for each biomarker recognition. The optical response obtained from the biosensor through the readout platform is capable to recognize specifically the desired proteins in the concentrations range for control eye (CE) and dry eye syndrome (DES). Preliminary results obtained will allow the development of a dry eye detection device useful in the area of ophthalmology and applicable to other possible diseases related to the eye dysfunction.

It is known that retinopathies may affect arteries and veins differently. Therefore, reliable differentiation of arteries and veins is essential for computer-aided analysis of fundus images. The purpose of this study is to validate one automated method for robust classification of arteries and veins (A-V) in digital fundus images. We combine optical density ratio (ODR) analysis and blood vessel tracking algorithm to classify arteries and veins. A matched filtering method is used to enhance retinal blood vessels. Bottom hat filtering and global thresholding are used to segment the vessel and skeleton individual blood vessels. The vessel tracking algorithm is used to locate the optic disk and to identify source nodes of blood vessels in optic disk area. Each node can be identified as vein or artery using ODR information. Using the source nodes as starting point, the whole vessel trace is then tracked and classified as vein or artery using vessel curvature and angle information. 50 color fundus images from diabetic retinopathy patients were used to test the algorithm. Sensitivity, specificity, and accuracy metrics were measured to assess the validity of the proposed classification method compared to ground truths created by two independent observers. The algorithm demonstrated 97.52% accuracy in identifying blood vessels as vein or artery. A quantitative analysis upon A-V classification showed that average A-V ratio of width for NPDR subjects with hypertension decreased significantly (43.13%).

Optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) are two state-of-the-art imaging technologies commonly used to study retina. Adaptive Optics (AO) methodologies enable high-fidelity correction of ocular aberrations, resulting in improved resolution and sensitivity for both SLO and OCT systems. Here we present work integrating OCT into a previously described mouse retinal AO-SLO system, allowing simultaneous reflectance and fluorescence imaging. The new system allows simultaneous data acquisition of AO-SLO and AO-OCT, facilitating registration and comparison of data from both modalities. The system has data acquisition speed of 200 kHz A-scans/pixel, and high volumetric resolution.

With the onset of clinically available spectral domain (SD-OCT) and swept source (SS-OCT) systems, clinicians are now easily able to recognize sub retinal microstructure and vascularization in the choroidal and scleral regions. As the bloodrich choroid supplies nutrients to the upper retinal layers, the ability to monitor choroid function accurately is of vital importance for clinical assessment of retinal health. However, the physical appearance of the choroid blood vessels (darker under a healthy Retinal Pigmented Epithelium (RPE) compared to regions displaying an RPE atrophic lesion) has led to confusion within the OCT ophthalmic community. The differences in appearance between each region in the OCT image may be interpreted as different vascular patterns when the vascular networks are in fact very similar. To explain this circumstance, we simulate light scattering phenomena in the RPE and Choroid complexes using the finite difference time domain (FDTD) method. The simulation results are then used to describe and validate imaging features in a controlled multi-layered tissue phantom designed to replicate human RPE, choroid, and whole blood microstructure. Essentially, the results indicate that the strength of the OCT signal from choroidal vasculature is dependent on the health and function of the RPE, and may not necessarily directly reflect the health and function of the choroidal vasculature.

Vitreoretinal surgery is moving towards 3D visualization of the surgical field. This require acquisition system capable of recording such 3D information. We propose a proof of concept imaging system based on a light-field camera where an array of micro-lenses is placed in front of a conventional sensor. With a single snapshot, a stack of images focused at different depth are produced on the fly, which provides enhanced depth perception for the surgeon. Difficulty in depth localization of features and frequent focus-change during surgery are making current vitreoretinal heads-up surgical imaging systems cumbersome to use. To improve the depth perception and eliminate the need to manually refocus on the instruments during the surgery, we designed and implemented a proof-of-concept ophthalmoscope equipped with a commercial light-field camera. The sensor of our camera is composed of an array of micro-lenses which are projecting an array of overlapped micro-images. We show that with a single light-field snapshot we can digitally refocus between the retina and a tool located in front of the retina or display an extended depth-of-field image where everything is in focus. The design and system performances of the plenoptic fundus camera are detailed. We will conclude by showing in vivo data recorded with our device.

Changes in visibility of the Henle fiber layer and photoreceptor bands of the human retina with illumination directionality have been reported in OCT clinical imaging. These are a direct consequence of the changes in back scattering due to fibrous tissue orientation and to waveguiding properties of the photoreceptors respectively. Here we report the preliminary results of a study on the effects of retinal images acquired with OCT of illumination directionality in the mouse retina. The quantitative assessment of the reflectivity of retinal layers of a BALB/c and WT pigmented mice was performed in-vivo using a swept-source optical coherence tomography system. The intensities of backscattered signals from different outer retinal layers were measured and compared.

The high dust content in air of a working zone causes prevalence of pathologies of the anterior segment of the eye of workers of cement production. Therefore, studying of features of cement dust impact on structure of a cornea and development of ways of eye protection from this influence is relevant. In this work experimental studies were carried out with twenty eyes of ten rabbits. OCTtomography was used to monitor the light attenuation coefficient of the cornea in vitro during the permeability of cement dust and/or keratoprotector (Systein Ultra). The permeability coefficients of the cornea for water, cement dust and keratoprotector were measured. A computer model allowing one to analyze the diffusion of these substances in the eye cornea was developed. It was shown that 1) the cement dust falling on the eye cornea caused pronounced dehydration of the tissue (thickness decreasing) and led to the increase of the attenuation coefficient, which could affect the deterioration of the eyesight of workers in the conditions of cement production; 2) the application of the keratoprotector to the eye cornea when exposed by cement dust, slowed significantly the dehydration process and did not cause the increase of the attenuation coefficient that characterized the stabilization of visual functions. At this, the keratoprotector itself did not cause dehydration and led to the decrease of the attenuation coefficient, which could allow it to be used for a long time in the order to protect the organ of vision from the negative effects of cement dust.

Glaucoma is caused by a pathological rise in the intraocular pressure, which results in a progressive loss of vision by a damage to retinal cells and the optical nerve head. Early detection of pressure-induced damage is thus essential for the reduction of eye pressure and to prevent severe incapacity or blindness. Within the new European Project GALAHAD (Glaucoma Advanced, Label free High Resolution Automated OCT Diagnostics), we will develop a new low-cost and high-resolution OCT system for the early detection of glaucoma. The device is designed to improve diagnosis based on a new system of optical coherence tomography. Although OCT systems are at present available in ophthalmology centres, high-resolution devices are extremely expensive. The novelty of the new Galahad system is its super wideband light source to achieve high image resolution at a reasonable cost. Proof of concept experiments with cell and tissue Glaucoma test standards and animal models are planned for the test of the new optical components and new algorithms performance for the identification of Glaucoma associated cell and tissue structures. The intense training of the software systems with various samples should result in a increased sensitivity and specificity of the OCT software system.

The international standard ISO 12312-1 proposes transmittance tests that quantify how dark sunglasses lenses are and whether or not they are suitable for driving. To perform these tests a spectrometer is required. In this study, we present and analyze theoretically an accurate alternative method for performing these measurements using simple components. Using three LEDs and a four-channel sensor we generated weighting functions similar to the standard ones for luminous and traffic lights transmittances. From 89 sunglasses lens spectroscopy data, we calculated luminous transmittance and signal detection quotients using our obtained weighting functions and the standard ones. Mean-difference Tukey plots were used to compare the results. All tested sunglasses lenses were classified in the right category and correctly as suitable or not for driving. The greatest absolute errors for luminous transmittance and red, yellow, green and blue signal detection quotients were 0.15%, 0.17, 0.06, 0.04 and 0.18, respectively. This method will be used in a device capable to perform transmittance tests (visible, traffic lights and ultraviolet (UV)) according to the standard. It is important to measure rightly luminous transmittance and relative visual attenuation quotients to report correctly whether or not sunglasses are suitable for driving. Moreover, standard UV requirements depend on luminous transmittance.

Lasers are employed for numerous medical interventions by exploiting ablative, disruptive or thermal effects. In ocular procedures, lasers have been used for decades to treat diseases such as diabetic retinopathy, macular edema and aged related macular degeneration via photocoagulation of retinal tissues. Although laser photocoagulation is well established in today’s practice, efforts to improve clinical outcomes by reducing the collateral damage from thermal diffusion is leading to novel treatments using shorter (μs) laser pulses (e.g. selective retinal therapy) which result in physical rather than thermal damage. However, for these new techniques to be widely utilized, a method is required to ensure safe but sufficient dosage has been applied, since no visible effects can be seen by ophthalmoscopy directly post treatment. Photoacoustic feedback presents an attractive solution, as the signal is dependent directly on absorbed dosage. Here, we present a method that takes advantage of temporal pulse formatting technology to minimize variation in absorbed dose in ophthalmic laser treatment and provide intelligent dosimetry feedback based on photoacoustic (PA) response. This method tailors the pulse to match the frequency response of the sample and/or detection chain. Depending on the system, this may include the absorbing particle size, the laser beam diameter, the laser pulse duration, tissue acoustic properties and the acoustic detector frequency response. A significant improvement (<7x) of photoacoustic signal-to-noise ratio over equivalent traditional pulse formats have been achieved, while spectral analysis of the detected signal provides indications of cavitation events and other sample properties.