Biomedical optics express最新文献

Cataract surgery involves the implantation of an intraocular lens (IOL) to replace the opacified crystalline lens. Monofocal IOLs, the most common type, are intended to have the eye in focus at a given distance, usually at infinity. Simultaneous vision IOLs (SVIOLs) and extended depth of focus (EDOF) aim to minimize postoperative dependence on spectacles by providing either multiple foci or an extended depth of focus. These lenses utilize a variety of diffractive and refractive designs to achieve varied focal depths. While common optical testing methods based on the IOL's modulation transfer function (MTF) or resolving power at best focus are essential for quality control, they do not fully address the lenses' performance requirements in daily visual tasks such as reading in a variety of distances. The purpose of this work was to introduce a visually relevant on-bench test method, which includes an image analysis technique and a visual acuity-related image quality metric, to evaluate the through-focus performance of different commercially available IOLs. This method consists of recording a series of optotype images in a realistic eye model with the IOL, adjusting the stimulus vergence through a focus-tunable lens. We compare the results obtained with mono-focal, enhanced mono-focal, EDOF, and (diffractive) trifocal IOLs.

We derive analytical expressions to describe how light is frequency-shifted when interacting with ultrasound within scattering media, due to the modulation of the refractive index induced by the ultrasound pressure waves. The model is validated through Monte Carlo simulations, works for high ultrasound pressures, and allows for many simultaneous ultrasound waves or frequency components, which is important due to the non-linear propagation effects in tissue. We also provide critical insights into how the ultrasound properties can be optimized for an enhanced efficiency of the light to be frequency-shifted, facilitating applications in ultrasound optical tomography and other photonic diagnostic techniques.

In this work, we present two new multifocal intraocular lens (MIOL) designs, both based on the silver mean kinoform diffractive lens. We demonstrate that a single aperiodic diffractive profile can be used to create two different MIOLs: one with a kinoform structure and the other with a stepwise profile. Quantitative assessment of the designs was carried out using the through focus modulation transfer function and the area under the modulation transfer function for the prediction of their visual performance. Our results show that both designs exhibit nearly identical optical performance at the design wavelength (λ = 550 nm), though their intrinsic longitudinal chromatic aberration differs significantly. Given that diffractive extended depth of focus (EDoF) intraocular lenses are prone to image degradation due to dysphotopic phenomena, we also compared the halos generated by these two designs and found notable differences in their behavior. Furthermore, under photopic conditions, the proposed lens designs demonstrated the potential to achieve visual acuity values of 0.2 logMAR or better across a vergence range from approximately 0 to 2 D. Finally, to qualitatively assess the behavior of the MIOLs, an objective experimental evaluation was conducted using an adaptive optics visual simulator in a model eye. Experimental results align with the quantitative assessment of the proposed designs.

Thyroid vascularization and hemodynamics become altered in thyroid pathologies and could thus inform diagnostics, therapy planning, and follow-up. However, the current non-invasive monitoring methods available in clinics lack the necessary sensitivity and/or are impractical for large-scale deployment. As a step towards proposing a new modality, we applied the first platform, to our knowledge, designed to do simultaneous measurements of neck anatomy and thyroid microvascular hemodynamics and metabolism in a single probe placement, integrating state-of-the-art near-infrared spectroscopy techniques and clinical ultrasound. A rich dataset was formed with sixty-five subjects (forty-eight females), including eighteen healthy volunteers and forty-seven patients with thyroid nodules, characterizing thyroid tissue and the effects of demographic and anatomical variables while preserving the standard clinical workflow. We have found marked reductions with age and body mass index in thyroid total hemoglobin concentration (THC), tissue oxygen saturation (StO ₂), and blood flow index (BFi), among others. Patients showed lower THC and BFi than healthy subjects, and the limited sample of malignant nodules showed a higher StO ₂ than the benign. These findings support the need for personalized clinical approaches.

Cortical computations arise from patterns of neuronal activity that span across all cortical layers and cell types. Three-photon excitation has extended the depth limit of in vivo imaging within the mouse brain to encompass all cortical layers. However, simultaneous three-photon imaging throughout cortical layers has yet to be demonstrated. Here, we combine non-unity magnification remote focusing with adaptive optics to achieve single-cell resolution imaging from two temporally multiplexed planes separated by up to 600 µm. This approach enables the simultaneous acquisition of neuronal activity from genetically defined cell types in any pair of cortical layers across the mouse neocortical column.

Intraocular lenses (IOLs) are routinely used to replace cataractous crystalline lenses. Most current models have a biconvex design that reduces optical quality in the periphery since they are optimized only for central vision. Inverted meniscus IOLs are optimized to achieve similar optical performance to phakic eyes in the peripheral retina. Additionally, biconvex IOLs have been predicted to induce image shifts in the peripheral visual field. The aim of this study was to evaluate whether inverted meniscus IOLs produce a more consistent object-to-image mapping on the retina. For this purpose, retinal images before and after IOL implantation were recorded in subjects implanted with either standard biconvex or inverted meniscus IOLs, and the positions of landmarks were compared. The results showed that radial displacement of retinal landmarks increased with eccentricity in biconvex IOLs, as expected, but tended to have a flatter progression with smaller values in patients implanted with inverted meniscus lenses.

A new system and methodology are introduced to evaluate photic phenomena induced by different intraocular lens (IOL) technologies using a "see-through" IOL analyzer system in phakic subjects. Nineteen phakic subjects looked through the Groningen IOL Telescope type 1 (GIT1) system under different conditions. Four different IOL designs with different clinical levels of photic phenomena were evaluated by the subjects. Subjects were asked to give a subjective rating of each lens and perform a psychophysical test. The results of this study were compared to the clinical outcomes of the subjective perception of halo, glare, and starbursts of cataract patients implanted with the same IOL models. Depending on the visual test performed, a good correlation can be found between the tests performed here and the bother levels of real cataract patients. The results validate the use of this methodology to evaluate preclinical visual symptoms. The system could be a powerful tool for the design and development of new optical designs.

Imaging depth-resolved birefringence and optic axis orientation with polarization sensitive optical coherence tomography (PS-OCT) unveils details of tissue structure and organization that can be of high pathophysiologic, mechanistic, and diagnostic value. For catheter-based PS-OCT, the dynamic rotation of the fiber optic probe, in addition to the polarization effects of the system components, complicates the reliable and robust reconstruction of the sample's optic axis orientation. Addressing this issue, we present a new method for the reconstruction of absolute depth-resolved optic axis orientation in catheter-based PS-OCT by using the intrinsic retardance of the protecting catheter sheath as a stable guide star signal. Throughout the paper, we rigorously inspect the retardance and optic axis orientation of the sheath and validate our method by imaging a birefringent phantom with known optic axis orientation. Reconstructing the optic axis orientation of the phantom, placed at different locations around the catheter, we measured an average absolute deviation (AAD) for the mean optic axis orientation over cross-sectional images of 3.28°, even with significant bending stress on the catheter. This corresponds to an almost three-fold improvement compared to our earlier method (optic axis AAD of 9.41°). We finally highlight the capability of our reconstruction with stereotactic catheter-based PS-OCT of a fresh sheep brain.

This study investigates whether a diffractive presbyopia-correcting multifocal intraocular lens disrupts the favorable interaction between chromatic and monochromatic aberrations in the eye. This is analyzed not only for distant objects but also for closer viewing distances, where the lens utilizes different diffraction orders depending on its design. We consider diffractive designs based on the zero-diffraction order for far vision and the first diffraction order for near vision (i.e., 0F/+1N design). Within the limitations of clinical visual acuity examination in various groups of subjects, our results prove that diffractive presbyopia-correcting lenses with 0F/+1N design preserve the beneficial interaction between chromatic and monochromatic aberrations at both far and near vision. The results are obtained for lenses with varying energy efficiency distributions between the far and near focal points, ranging from balanced (bifocal contact lens) to far-dominant (50% far, 30% near in a trifocal intraocular lens) configurations. These findings are specific to the 0F/+1N design and cannot be extrapolated to other diffractive lens types.

Polarization-resolved second harmonic generation (pSHG) is a label-free method that has been used in a range of tissue types to describe collagen orientation. In this work, we develop pSHG analysis techniques for investigating cranial bone collagen assembly defects occurring in a mouse model of hypophosphatasia (HPP), a metabolic bone disease characterized by a lack of bone mineralization. After observing differences in bone collagen lamellar sheet structures using scanning electron microscopy, we found similar alterations with pSHG between the healthy and HPP mouse collagen lamellar sheet organization. We then developed a spatial polarimetric gray-level co-occurrence matrix (spGLCM) method to explore polarization-mediated textural differences in the bone collagen mesh. We used our spGLCM method to describe the collagen organizational differences between HPP and healthy bone along the polarimetric axis that may be caused by poorly aligned collagen molecules and a reduction in collagen density. Finally, we applied machine learning classifiers to predict bone disease state using pSHG imaging and spGLCM methods. Comparing random forest (RF) and XGBoost technique on spGLCM, we were able to accurately separate unknown images from the two groups with an averaged F1 score of 92.30%±3.11% by using RF. Our strategy could potentially allow for monitoring of therapeutic efficacy and disease progression in HPP, or even be extended to other collagen-related ailments or tissues.