The Portable Eye Examination Kit : mobile phones can screen for eye disease in low-resource settings

The Portable Eye Examination Kit (Peek) is being tested in field trials in Kenya, Mali, Malawi, Tanzania, Botswana, Madagascar, India, and the United Kingdom, and testing in more countries is planned in the future. Peek is a comprehensive and integrated smartphone-based tool kit that comprises the full set of core tests needed for eye screening, designed to be used by operators with minimal to no training. It is composed of a smartphone app and a low-cost adapter for retinal imaging, both optimized for ease of use, and it allows operators to test for the core vision problems-testing for visual acuity, color, and contrast sensitivity, image grading cataracts-and for photos of the back of the eye to be taken, saved, and sent to experts for diagnosis, follow-up, and arranging treatment. Peek's primary aim is not to enhance or replace existing diagnostics tools. Rather, Peek aims to link patients with eye care providers. Peek is specifically oriented and optimized toward eye screening in the community. With this, it helps to identify, directly in the community, by nonspecialist community workers, the people who need to be seen by an ophthalmologist, increasing access to high-quality eye care

Diffuse reflectance measurement tool for laparoscopic surgery

Continuous-wave diffuse reflectance or Near Infrared Spectroscopy (NIRS) offers the possibility to perform a preliminary screening of tissue for ischemia or other tissue anomalies. A tool for intracavity NIRS measurements during laparoscopic surgery, developed within the framework of the FP7-IP ARAKNES (Array of Robots Augmenting the KiNematics of Endoluminal Surgery) project, is described. It consists of a probe, that is located on the tip of an appropriately shaped laparoscopic manipulator and then applied to the tissue. Such a probe employs an array of incoherent semiconductor light sources (LEDs) frequency-multiplexed on a single detector using a lock-in technique. The resulting overall tool structure is simple and compact, and allows efficient coupling of the emitted light towards the tissue. The tool has high responsivity and enables fast and accurate measurements. A dataset gathered from in-vivo tissue is presented. The performance both indicates direct applicability of the tool to significant surgical issues (ischemia detection), and clearly indicates the possibility of further miniaturizing the probe head towards catheterized approaches

Portable instrument for in-vivo infrared oxymetry using spread-spectrum modulation

Near Infrared Spectroscopy (NIRS) can be employed to monitor noninvasively and continuously local changes in hemodynamics and oxygenation of human tissues. A portable NIRS research-grade acquisition system, dedicated to measurements during muscular exercise, is presented. The instrument is able to control up to eight LED sources and two detectors. A digital correlation technique, implemented on a single-chip RISC microcontroller, performs source-to-detector multiplexing. Such algorithm is highly optimized for computational efficiency and ambient noise rejection. Software-configurable input stages allow for flexibility in instrument setup. As a result of the specific correlation technique employed, the instrument is compact, lightweight and efficient. Clinical tests on oxygen consumption show excellent performance

Near-infrared spectroscopy study of tourniquet-induced forearm ischaemia in patients with coronary artery disease

Near-Infrared Spectroscopy (NIRS) can be employed to monitor local changes in haemodynamics and oxygenation of human tissues. A preliminary study has been performed in order to evaluate the NIRS transmittance response to induced forearm ischaemia in patients with coronary artery disease (CAD). The population consists in 40 patients with cardiovascular risk factors and angiographically documented CAD, compared to a group of 13 normal subjects. By inflating and subsequently deflating a cuff placed around the patient arm, an ischaemia has been induced and released, and the patients have been observed until recovery of the basal conditions. A custom NIRS spectrometer (IRIS) has been used to collect the backscattered light intensities from the patient forearm throughout the ischaemic and the recovery phase. The time dependence of the near-infrared transmittance on the control group is consistent with the available literature. On the contrary, the magnitude and dynamics of the NIRS signal on the CAD patients show deviations from the documented normal behavior, which can be tentatively attributed to abnormal vessel stiffness. These preliminary results, while validating the performance of the IRIS spectrometer, are strongly conducive towards the applicability of the NIRS technique to ischaemia analysis and to endothelial dysfunction characterization in CAD patients with cardiovascular risk factors

Machine learning as an enabler of medical technology

Driven by advancements in digital computing, data storage, and the availability of large datasets from digitized healthcare workflows and telemedicine, machine learning is swiftly becoming integral to the most diverse aspects of medical technology. It's not merely about optimizing complex clinical tasks; it's also about fostering innovative applications such as large-scale image screening, data inference, and automatic diagnostics. Indeed, machine learning is a prerequisite for a radically new approach to these tasks, transcending the re-implementation of established technologies. This special issue spotlights papers where machine learning is an essential constituent of medical technology innovation

Probing for local activity-related modulation of the infrared backscattering of the brain cortex

The possibility to measure the metabolic activity of the brain cortex, with submillimeter spatial and subsecond temporal resolution, would open up enticing scenarios in addressing basic issues on the relation between different structural components of brain signal processing, and in providing an operational pathway to interaction with (dis)functional signal patterns. In the present article, we report the description of a simple system that allows the detection of the minute changes that occur in the optical backscattering of the cortex as a metabolic response to external stimuli. The simplicity of the system is compatible with scalability to an implantable probe. We validate the system on an animal model, and we propose an algorithm to extract meaningful data from the measured signal. We thus show the detection of individual haemodynamic cortical responses to individual stimulation events, and we provide operational considerations on the signal structure

Laplacian-based focus measure allows rapid focus estimation of annular regions in gray-scale images

Important ophthalmic imaging techniques, such as fundus camera imaging, utilize light sources that need to be focused on an annular section of an eye surface. In order to be performed dynamically, this requires real-time control of the focus plane of the illumination optics. When considering adaptive focusing in ophthalmic instruments, liquid lenses represent the best compromise in terms of tunability, tuning range, compactness, numerical aperture, and speed. In recent years, several compact eye imaging devices using liquid lenses have been described in the literature. These would benefit from low computational complexity algorithms for adaptive local auto-focus on an annular region, to allow the illumination optics to be controlled by low-cost and low-power electronics. In this paper, we propose a novel radial-focus evaluation method based on a revised version of a more traditional Laplacian-based focus estimator. This radial focus evaluation is targeted to focusing annular sections of an image, with the advantage of a drastic reduction of computational complexity

Frequency dependence of the dielectric and electro-optic response in suspensions of charged rod-like colloidal particles

We have performed an experimental investigation on the electrokinetic properties of charged rod-like fluorinated latex colloids. Systematic measurements of electrophoretic mobility, dielectric constant and electric birefringence have been performed as a function of the concentration of added nonionic surfactant and salt. In the investigated range of parameters, the zeta potential is a strongly decreasing function of the concentration of nonionic surfactant, while it is basically independent from ionic strength. We have obtained the frequency dependence of dielectric constant and Kerr constant as a function of zeta-potential and ionic strength. We observe the transition from a low frequency behavior, where both the dielectric constant and the Kerr constant are enhanced by the presence of the double layer, to a high frequency behavior, where both quantities take the value expected for unchanged particles in an insulating medium. The shape of the frequency dispersion of the Kerr constant coincides with that of the dielectric constant, but the cut-off frequencies are the same only when the zeta-potential of the particles is low

Clinical validation of a smartphone-based adapter for optic disc imaging in Kenya

Visualization and interpretation of the optic nerve and retina are essential parts of most physical examinations. To design and validate a smartphone-based retinal adapter enabling image capture and remote grading of the retina. This validation study compared the grading of optic nerves from smartphone images with those of a digital retinal camera. Both image sets were independently graded at Moorfields Eye Hospital Reading Centre. Nested within the 6-year follow-up (January 7, 2013, to March 12, 2014) of the Nakuru Eye Disease Cohort in Kenya, 1460 adults (2920 eyes) 55 years and older were recruited consecutively from the study. A subset of 100 optic disc images from both methods were further used to validate a grading app for the optic nerves. Data analysis was performed April 7 to April 12, 2015. Vertical cup-disc ratio for each testwas compared in terms of agreement (Bland-Altman and weighted κ) and test-retest variability. A total of 2152 optic nerve images were available from both methods (also 371 from the reference camera but not the smartphone, 170 from the smartphone but not the reference camera, and 227 from neither the reference camera nor the smartphone). Bland-Altman analysis revealed a mean difference of 0.02 (95%CI, −0.21 to 0.17) and a weighted κ coefficient of 0.69 (excellent agreement). The grades of an experienced retinal photographer were compared with those of a lay photographer (no health care experience before the study), and no observable difference in image acquisition quality was found. Nonclinical photographers using the low-cost smartphone adapter were able to acquire optic nerve images at a standard that enabled independent remote grading of the images comparable to those acquired using a desktop retinal camera operated by an ophthalmic assistant. The potential for task shifting and the detection of avoidable causes of blindness in the most at-risk communities makes this an attractive public health intervention