The roles of birefringence and scattering of polarized light are considered in the visual perception of Haidinger's and Boehm’s brushes, both entopic phenomena. To simulate the phenomena, we developed and employed a theoretical polarization-based computational model that imitated the optical system geometry of the human eye. Using this model, we demonstrated that Haidinger's brushes originate because the structured organization of Henle's fibre layer, which act as the analyser to the polarized light, causes birefringence. Because of the radial orientation of these fibres, Haidinger's brushes appear perpendicular to the orientation of the incident linear polarization of light. Additionally, the results of Monte Carlo-based modelling confirm that Boehm’s brushes, which are perceived outside the macula region, are the product of low-order scattering of polarised light in the superficial layer of the retina. Understanding of these phenomena, in terms of their formation and appearance, is essential for basic and clinical studies on visual perception, including the development of advanced ophthalmic tools for assessing macular and retina functions.

We present a new experimental setup specialized in creating retinal models with real human blood flow that controls or measure many sources of imaging variability. This will assist with extracting the core physical principles required to better understand in-vivo OCT, doppler OCT, and spectroscopic SLO data, to build better retinal imaging devices. Our setup consists of two components, developed simultaneously. The first component is a flow system with the calibration methods needed to drive human whole blood through a closed-loop system. Controls include fluid pressure/flow rate (via pump speed) and the oxygenation level of the blood (via a gas exchange component). This results in a flow characterized by sensors measuring blood oxygenation saturation, temperature, pH, and flow rate through our model eye. The second setup component is the model eye. We have created silicone elastomer-based phantoms with flow channel diameters matching typical vasculature dimensions of a human retina (50 – 150 µm). These phantoms are embedded in a custom-built housing which mimics the optics of the eye. This makes the flow medium running through the phantom’s capillary easily accessible by any optical measurement technique for analysis. The optical scattering properties of the model eye, as well as phantom geometry, can be manipulated at fabrication to suit the requirements of the experiments being performed, and can be easily interchanged in the flow system. We present initial results on imaging the flow channel with an intralipid scattering medium and human whole-blood using an optical coherence tomography (OCT) setup built for ophthalmic applications. The goal of this research project is to quantify blood flow velocity from the dynamic OCT speckle patterns seen in sequential flow-channel images (Doppler OCT).

This Conference Presentation, Emerging methods of optical elastography for ocular biomechanics, was recorded at Photonics Europe Strasbourg France.

The field of biophotonics embraces biomedical applications of light, particularly in diagnostics (e.g., optical bioimaging) and therapeutics (e.g., light induced therapy) of cancer and other diseases. At the same time, the biomedical field has been greatly advancing through a nanotechnology, which offers a platform for targeted drug delivery and multimodal medical imaging. Merging nanotechnology and biophotonics approaches resulted in a development of multiple nanoplatforms combining optical diagnostic and phototherapeutic capabilities; optical imaging guided nanotherapeutics is among the most intensively developing directions in nanobiotechnology. In the last few years, we have been working on inorganic and organic nanomaterials for optical bioimaging and imaging guided phototherapy, along with a development of the advanced optical imaging modalities. This talk will present our recent results on development of heterogeneous nanoparticles that can be detected/ imaged/ differentiated in vitro and in vivo using near infrared (NIR) luminescence imaging. The proposed nanoplatforms comprise polymeric, lipid or protein nanoparticles along with rare earth ion doped fluoride nanocrystals, as well as their nanoblends with NIR fluorescent organic dyes and other functional small molecules, including molecular agents for chemo and photoinduced therapies of cancer. Spectral and temporal features of the photoluminescence from the developed nanoformulations allow for using them as imaging agents in hyperspectral, time-gated and luminescence lifetime imaging. While possessing the NIR imaging contrast and therapeutic functionality, the NIR emitting nanoformulations can also be garnished with other medical imaging modalities (e.g., computed tomography, CT, photoacoustic imaging, PAI), providing a single nanoagent for multiple imaging techniques and enabling the integration of cellular, tissue and whole body imaging. The talk will demonstrate examples of applications of nanoparticles as multimodal imaging guided therapeutic agents and conclude with a discussion on the challenges and opportunities in the domain of optically active nanoformulations for NIR imaging guided phototherapies of cancer and other diseases.

Preterm birth, defined as delivery at less than 37 weeks of gestation, is the leading cause of newborns mortality. The survivors may have life-long problems including neurological, hearing, respiratory and vision disorders. Preterm birth is often linked to the premature remodeling of the extracellular matrix of cervical collagen resulting from structural defects, infection or often unknown causes. The process of cervical remodeling, namely, the transformation of uterine cervix from a closed rigid structure to a compliant one for safe passage of the fetus, is a crucial stage of normal parturition, but this process can be drastically accelerated in preterm birth. We explore the potential of Mueller polarimetry to detect these alterations of the extracellular matrix of cervical collagen early enough in order to provide the quantitative assessment of the preterm birth risk by polarimetric scoring of collagen. Unstained thin sections of the whole uterine cervices from both non-pregnant and pregnant mice were studied with the custom-built transmission Mueller matrix microscope. The results of statistical analysis and multi-Gaussian fit of the distributions of depolarization and linear retardance parameters of cervical tissue sections demonstrated that imaging Mueller polarimetry in the visible wavelength range is very sensitive to the changes of extracellular matrix of cervical collagen with pregnancy. The circular arrangement of cervical collagen fibers around cervical os (that was observed for all non-pregnant mice) is lost through the whole length of mouse cervix one day before delivery. It suggests that the remodeling of cervical collagen may be evaluated in the direct observations with polarized light during the colposcopy test in late pregnancy. Thus, imaging Mueller polarimetry may serve as a fast and non-contact optical modality for the collagen scoring in pregnancy and the quantitative assessment of the preterm birth risk.

The use of different 3D printing technologies for pharmaceutical manufacturing provides new opportunities for personalized medicine with adjusted doses in various shapes and structures. In this work, we present a novel manufacturing method of printing personalized dosage forms onto edible wafer papers as orodispersible thin films, targeting diseases such as types of cancer. Orodispersible films (ODFs) hold promise as a novel drug delivery method as they are easy to administer to young and older patients, bypass absorption by the digestive system and minimize the risk of partial loss of actives due to table crashing or imprecise liquid administration. LIFT technology could be used to “print” paclitaxel molecules on various surfaces that could be used as depot formulations. Laser-Induced Forward Transfer (LIFT) has been successfully applied in the nanosecond regime for the controlled transfer of paclitaxel solution onto the receiving substrates. Quantification studies of printed paclitaxel amount were determined by means of a Mass Spectrometry (MS)-based analytical technique. Furthermore, initial studies were performed where the printed paclitaxel wafer papers were used as orodispersible films (ODFs) on mice for oral mucosal drug delivery application, revealing encouraging results.