Nasopharyngeal (NP) swab sampling is an effective approach for the diagnosis of coronavirus disease 2019 (COVID-19). Medical staffs carrying out the task of collecting NP specimens are in close contact with the suspected patient, thereby posing a high risk of cross-infection. We propose a low-cost miniature robot that can be easily assembled and remotely controlled. The system includes an active end-effector, a passive positioning arm, and a detachable swab gripper with integrated force sensing capability. The cost of the materials for building this robot is 55 USD and the total weight of the functional part is 0.23kg. The design of the force sensing swab gripper was justified using Finite Element (FE) modeling and the performances of the robot were validated with a simulation phantom and three pig noses. FE analysis indicated a 0.5mm magnitude displacement of the gripper’s sensing beam, which meets the ideal detecting range of the optoelectronic sensor. Studies on both the phantom and the pig nose demonstrated the successful operation of the robot during the collection task. The average forces were found to be 0.35N and 0.68N, respectively. It is concluded that the proposed robot is promising and could be further developed to be used in vivo.

The lens provides refractive power to the eye and is capable of altering ocular focus in response to visual demand. This capacity diminishes with age. Current biomedical technologies, which seek to design an implant lens capable of replicating the function of the biological lens, are unable as yet to provide such an implant with the requisite optical quality or ability to change the focussing power of the eye. This is because the mechanism of altering focus, termed accommodation, is not fully understood and seemingly conflicting theories require experimental support which is difficult to obtain from the living eye. This investigation presents finite element models of the eye lens based on data from human lenses aged 16 and 35 years that consider the influence of various modelling parameters, including material properties, a wide range of angles of force application and capsular thickness. Results from axisymmetric models show that the anterior and posterior zonules may have a greater impact on shape change than the equatorial zonule and that choice of capsular thickness values can influence the results from modelled simulations.

Objective: The human visual system alters its focus by a shape change of the eye lens. The extent to which the lens can adjust ocular refractive power is dependent to a significant extent on its material properties. Yet, the link between the optics and mechanics of the lens remains uncertain and relatively unexplored. This study aims to investigate this opto-mechanical link within the eye lens to gain insight into the processes of shape alteration and their respective decline with age. Methods: Finite Element models based on biological lenses were developed for five ages: 16, 35, 40, 57 and 62 years by correlating in vivo measurements of the longitudinal modulus using Brillouin scattering with in vitro X-ray interferometric measurements of refractive index and taking into account various directions of zonular force. Results: A model with radial cortical Young's moduli provides the same amount of refractive power with lesser change in thickness than a model with uniform cortical Young's modulus and shows uniform stress distributions with no discontinuities along the cortico-nucleus boundary. The direction of zonular angles can significantly influence curvature change regardless of the modulus distribution. Conclusions: The present paper proposes a modelling approach, coupling optical and mechanical properties of human eye lens, which reveals the effect of parameter choice on model response. Significance: This advanced modelling approach, considering the important interplay between optical and mechanical properties, has potential for use in design of accommodating implant lenses and for investigating non-biological causes of pathological processes in the lens (e.g. cataract).

The development of the eye requires the co-ordinated integration of optical and neural elements to create a system with requisite optics for the given animal. The eye lens has a lamellar structure with gradually varying protein concentrations that increase towards the centre, creating a gradient refractive index or GRIN. This provides enhanced image quality compared to a homogeneous refractive index lens. The development of the GRIN during ocular embryogenesis has not been investigated previously. This study presents measurements using synchrotron X-ray Talbot interferometry and scanning electron microscopy of chick eyes from embryonic day 10: midway through embryonic development to E18: a few days before hatching. The lens GRIN profile is evident from the youngest age measured and increases in magnitude of refractive index at all points as the lens grows. The profile is parabolic along the optic axis and has two distinct regions in the equatorial plane. We postulate that these may be fundamental for the independent central and peripheral processes that contribute to the optimisation of image quality and the development of an eye that is emmetropic. The spatial distributions of the distinct GRIN profile regions match with previous measurements on different fibre cell groups in chick lenses of similar developmental stages. Results suggest that tissue compaction may not be necessary for development of the GRIN in the chick eye lens.

In early corneal examinations, the relationships between the morphological and biomechanical features of the cornea were unclear. Although consistent links have been demonstrated between the two in certain cases, these are not valid in many diseased states. An accurate assessment of the corneal biomechanical properties is essential for understanding the condition of the cornea. Studies on corneal biomechanics in vivo suggest that clinical problems such as refractive surgery and ectatic corneal disease are closely related to changes in biomechanical parameters. Current techniques are available to assess the mechanical characteristics of the cornea in vivo. Accordingly, various attempts have been expended to obtain the relevant mechanical parameters from different perspectives, using the air-puff method, ultrasound, optical techniques, and finite element analyses. However, a measurement technique that can comprehensively reflect the full mechanical characteristics of the cornea (gold standard) has not yet been developed. We review herein the in vivo measurement techniques used to assess corneal biomechanics, and discuss their advantages and limitations to provide a comprehensive introduction to the current state of technical development to support more accurate clinical decisions.

Purpose: To determine whether lens biomechanical or geometric changes contribute to the decline in the accommodative capacity of the human eye, and to examine any differences in zonular function between different age groups. Methods: Eighteen finite element whole eye models were developed to simulate the accommodative process. Six models were constructed in each of the two age cohorts, from the fourth and the sixth decades of life using data from ex vivo human lenses. An additional six models combining the material properties of lenses from the fourth decade with the geometry of those from the sixth decade were included. Optical lens models developed based on the results of mechanical simulations were used to calculate the central optical power (COP). Results: The change in COP was significantly greater for both the fourth-decade models and the mixed models compared with the sixth-decade models. The rates of the change in geometric parameters relative to the increment of change in COP in the mixed models were greater than those in the fourth-decade models. The distribution of zonular force was consistent across all three groups. However, the sixth-decade models and mixed models exhibited similar distributions of zonular angles, both of which were greater than those in the fourth-decade models. Conclusions: Both biomechanical and geometric age-related changes contribute to the accommodative decline, with the material property manifesting a more substantial impact. Age-related changes in the lens do not influence the distribution of zonular tension, but do affect the angles that the zonule makes with the lens surface.