Axisymmetric Thermal Finite Element Analysis of Effects of Intraocular Projector in the Human Eye.

Millions of people worldwide live with corneal opacity, which continues to be one of the leading causes of blindness. Corneal opacity is treatable. However, the surgical methods for treating this condition, such as corneal transplantation and keratoprosthesis, have many complications. The use of an intraocular projector is a promising approach to treat corneal blindness. Like any device using electrical power, an intraocular projection device produces heat, which could potentially damage eye tissue. Australian and international standards state that there cannot be an increase of temperature of 2 °C caused by an implanted device. In order to determine if these standards are met, a 2D axisymmetric thermal analysis of the projector in the human eye is conducted in ANSYS Workbench. With the projector operating at its maximum wattage, our analysis shows that an air gap extension within the projector will help maintain the temperature increase below 2 °C.

Temperature Elevation in the Human Eye Due To Intraocular Projection Prosthesis Device.

Corneal opacity is a leading cause of blindness worldwide. Corneal transplantation and keratoprosthesis can restore vision but have limitations due to the shortage of donor corneas and complications due to infection. A proposed alternative treatment using an intraocular projection prosthesis device can treat corneal disease. In this study, we perform a transient thermal analysis of the bionic eye model to determine the power the device can produce without elevating the eye tissue temperature above the 2°C limit imposed by the international standard for implantable devices. A 3D finite element model, including blood perfusion and natural convection fluid flow of the eye, was created. The device was placed 1.95 mm from the iris, which experienced less than 2°C rise in the tissue temperature at a maximum power dissipation of LED at 100 mW and microdisplay at 25 mW.

A study of the response of the human cadaver head to impact.

High-speed biplane x-ray and neutral density targets were used to examine brain displacement and deformation during impact. Relative motion, maximum principal strain, maximum shear strain, and intracranial pressure were measured in thirty-five impacts using eight human cadaver head and neck specimens. The effect of a helmet was evaluated. During impact, local brain tissue tends to keep its position and shape with respect to the inertial frame, resulting in relative motion between the brain and skull and deformation of the brain. The local brain motions tend to follow looping patterns. Similar patterns are observed for impact in different planes, with some degree of posterior-anterior and right-left symmetry. Peak coup pressure and pressure rate increase with increasing linear acceleration, but coup pressure pulse duration decreases. Peak average maximum principal strain and maximum shear are on the order of 0.09 for CFC 60 Hz data for these tests. Peak average maximum principal strain and maximum shear decrease with increasing linear acceleration, coup pressure, and coup pressure rate. Linear and angular acceleration of the head are reduced with use of a helmet, but strain increases. These results can be used for the validation of finite element models of the human head.

High-speed seatbelt pretensioner loading of the abdomen.

This study characterizes the response of the human cadaver abdomen to high-speed seatbelt loading using pyrotechnic pretensioners. A test apparatus was developed to deliver symmetric loading to the abdomen using a seatbelt equipped with two low-mass load cells. Eight subjects were tested under worst-case scenario, out-of-position (OOP) conditions. A seatbelt was placed at the level of mid-umbilicus and drawn back along the sides of the specimens, which were seated upright using a fixed-back configuration. Penetration was measured by a laser, which tracked the anterior aspect of the abdomen, and by high-speed video. Additionally, aortic pressure was monitored. Three different pretensioner designs were used, referred to as system A, system B and system C. The B and C systems employed single pretensioners. The A system consisted of two B system pretensioners. The vascular systems of the subjects were perfused. Peak anterior abdominal loads due to the seatbelt ranged from 2.8 kN to 10.1 kN. Peak abdominal penetration ranged from 49 mm to 138 mm. Peak penetration speed ranged from 4.0 m/s to 13.3 m/s. Three cadavers sustained liver injury: one AIS 2, and two AIS 3. Cadaver abdominal response corridors for the A and B system pretensioners are proposed. The results are compared to the data reported by Hardy et al. (2001) and Trosseille et al. (2002).