Purpose: Retinal diseases are the major cause of blindness in industrialized countries. A forecast reported that an estimated number of 196 million people will be affected by age related macular degeneration by 2020. While tremendous effort is made to develop novel therapeutic strategies to rescue retinal neurons and retinal pigment epithelium (RPE), optimal means to evaluate the effects of such treatments and diagnose the disease are still missing.
Methods: We developed an imaging modality, called transscleral optical phase imaging (TOPI), which is able to resolve the individual human RPE cells in-vivo with the help of adaptive optics. The technology is based on oblique flood illumination and provides cellular resolution. The resulting 16 Hz-imaging speed, 5.7° × 5.7° field of view system allows for the visualization and the quantification of RPE cells within 2 seconds. Thanks to the approval from the ethic committee (CER-VD N°2017-00976), we conducted a study on 7 healthy human participants, with different skin pigmentations, 3 men and 4 women having an average age of 26 years. In all subjects, the RPE cell layer could be imaged and cell density could be quantified.
Results: We show the RPE density and area analysis for 7 healthy subjects. The results of the analyses show comparable values to those found in the literature.
Conclusion: The results of the study on healthy subjects demonstrate that TOPI is able to image and quantify in-vivo the human RPE cells, within a time frame of a few seconds (typically 2 seconds). The next step is to transfer the technique into a clinical environment.
With the miniaturization of scanning mirrors and the emergence of wearable health monitoring, an intriguing step is to investigate the potential of a laser scanning ophthalmoscope (LSO) for retinal imaging with wearable glasses. In addition to providing morphological information of the retina, such as vasculature, LSO images could also be used to provide information on general health conditions. A compact eyeglass with LSO capability would give access, on demand, to retinal parameters without disturbing the subject’s activity. One of the main challenges in this field is the creation of a device that does not interrupt the user’s field of view. We report, to our knowledge, the first see-through ophthalmoscope. The system is analyzed with three-dimensional simulations and tested in a proof-of-concept setup with the same key parameters of a wearable device. Finally, image quality is analyzed by acquiring images of an ex-vivo human eye sample.
Vision process is ruled by several cells layers of the retina. Before reaching the photoreceptors, light entering the eye has to pass through a few hundreds of micrometers thick layer of ganglion and neurons cells. Macular degeneration is a non-curable disease of themacula occurring with age. This disease can be diagnosed at an early stage by imaging neuronal cells in the retina and observing their death chronically. These cells are phase objects locatedon a background that presents an absorption pattern and so difficult to see with standard imagingtechniques in vivo. Phase imaging methods usually need the illumination system to be on the opposite side of the sample with respect to theimaging system. This is a constraintand a challenge for phase imaging in-vivo. Recently, the possibility of performing phase contrast imaging from one side using properties of scattering media has been shown. This phase contrast imaging is based on the back illumination generated by the sample itself.
Here, we present a reflection phase imaging technique based on oblique back-illumination. The oblique back-illumination creates a dark field image of the sample. Generating asymmetric oblique illumination allows obtaining differential phase contrast image, which in turn can be processed to recover a quantitative phase image. In the case of the eye, a transcleral illumination can generate oblique incident light on the retina and the choroidal layer.The back reflected light is then collected by the eye lens to produce dark field image.
We show experimental results of retinal phase imagesin ex vivo samples of human and pig retina.
In-vivo imaging of the eye’s fundus is widely used to study eye’s health. State of the art Adaptive Optics devices can resolve features up to a lateral resolution of 1.5 um. This resolution is still above what is needed to observe sub-cellular structures such as cone cells (1-1.25 um diameter). This limit in resolution is due to the small numerical aperture of the eye when the pupil is fully dilated (max 0.24).
In our work, we overcome this limit using a non-standard illumination scheme. A laser beam is shined on the lateral choroid layer, whose scattered light is illuminating the eye’s fundus. Thanks to a Spatial Light Modulator the scattered light from the choroid layer can be manipulated to produce a scanning focus spot on the fundus. The intensity of the reflected light from the fundus is collected from the pupil and used for reconstructing the image.
Quantum Key Distribution together with its intrinsic security represent the more promising technology to meet the challenging requests of novel generation communication protocols. Beyond its relevant commercial interests, QKD is currently and deeply investigated in research fields as quantum information and quantum mechanics foundations, in order to push over the limits of the actual resources needed to ensure the security of quantum communication. Aim of the paper is to contribute to this open debate presenting our last experimental implementations concerning two novel quantum cryptographic schemes which do not require some of the most widely accepted conditions for realizing QKD. The first is Goldenberg-Vaidman1,2 protocol, in which even if only orthogonal states (that in principle can be cloned without altering the quantum state) are used, any eavesdropping attempt is detectable. The second is N093 protocol which, being based on the quantum counterfactual effect, does not even require any actual photon transmission in the quantum channel between the parties for the communication. The good agreement between theoretical predictions and experimental results represent a proof of principle of the experimental feasibility of the novel protocols.