No description available.

No description available.

No description available.

No description available.

This paper describes an electro-oculometer and analyzes the electronic circuits required to process the signal. This electro-oculometer is a passive, two-channel device which detects the eye orientation using commercially available electrodes attached near the eyes. The electro-oculometer is composed of a special amplifier followed by a parabolic filter. The amplifier has high common mode rejection ratio, low drift, and low input bias current. Both DC and AC analyses of the electro-oculometer have been performed. The common mode rejection ratio (CMRR) of the input stage of the device is computed both at low and high frequencies. The experimental data were then compared with theoretical results. A parabolic low pass filter was designed and implemented as part of the electro-oculometer. A parabolic filter was chosen because it gives a minimum overshoot step response. The input stage (preamplifier) of the electro-oculometer is modified so as to prevent a latch up problem. This latch up is a saturated state of the system. When the output of the system reaches saturation, the system cannot reset itself. The new configuration of the preamplifier does not require any extra active elements.

Combat-related blast injuries are occurring more frequently with the increased use of improvised explosive devices in current military conflicts. Though much research has focused on how the body responds to the relatively low loading rates associated with blunt trauma, little is known regarding the response of the body to the higher loading rates associated with blast trauma. While soldiers are surviving once-lethal blast events due to enhanced protective equipment, injuries such as those to the eye and face that were once considered inconsequential, can now be detrimental to long-term healthcare costs and quality of life. Although it is suggested primary blast overpressure (i.e., the shock wave) can cause severe eye injuries, there remains few empirical data in the literature that confirms this. Adding to this, there are currently no testing standards to assess the effectiveness of personal protective equipment during blast exposure. Expanding upon traditional research techniques within the field of injury biomechanics, the research in this dissertation focuses specifically on developing experimental and physical models of the eye, face, and orbit for blast overpressure exposure. Foremost, a porcine eye model is used to quantify eye injury risk from blast overpressure exposure. Subsequently, these biomechanical data are used to develop a physical model of the eye that can be used in lieu of cadaver specimens for blunt and blast loading. Lastly, military spectacles and goggles are examined for effectiveness at protecting the eye during blast exposure. Combined with detailed computer-aided design geometries, these data can be used to validate computational models of the eye, orbit, and face to blast loading. Results from these tests support one theory that shock waves may enter the skull through the orbit, alluding to future work that is essential to more fully understanding the physiological response of the brain and ocular motor system to blast exposure. Ultimately, the experimental methods and analysis techniques disseminated herein serve as a framework for future experimental work related to blast and other high-rate loading scenarios. / Ph. D.

Every year, more than 2.4 million eye injuries occur in the United States, with over 30,000 of those injured left blind in at least one eye as a result. Computer modeling is one of the most versatile ways to study ocular trauma, however, existing models lack accurate stress and strain properties for ocular globe rupture. A pressure system was built to examine static and dynamic globe rupture pressures for healthy postmortem human and porcine (pig) eyes. Maximum rupture stress for the quasi-static tests was found to be 11.17MPa for human tissue and 12.08MPa for porcine tissue, whereas stress for the dynamic tests was found to be 30.18MPa for human tissue and 26.01MPa for porcine tissue. Maximum rupture stress results correlate well with static material properties used in published research (9.4MPa), and dynamic properties of 23MPa found in published research. Healthy postmortem human eyes were ruptured statically and dynamically to determine the relationship between stress and strain for the ocular globe under intraocular pressure loading. Stress-strain relationships were investigated and values for the elastic modulus were found to be slightly lower than that previously published. This research shows that it is important to differentiate between tissue type, and static versus dynamic failure properties before drawing conclusions from computer models and other published research. Now that rupture can be accurately determined, safety systems designed to protect eyesight in automotive, sports, and military applications can also be applied to protect the quality of life for humans in these applications. / Master of Science

Airbags have been saving lives in automobile crashes for many years and are now being used in helicopters. The purpose of this study was to investigate the potential for ocular injuries to helicopter pilots wearing night vision goggles when the airbag is deployed. A nonlinear finite element model of the human eye was constructed. Ocular structures never before included in finite element models of the eye, such as the fatty tissue, extraocular muscles, and bony orbit were included in this model. In addition, this model includes material properties up to rupture making the eye suitable for large deformation applications. The model was imported into Madymo and used to determine the worst-case position of a helicopter pilot wearing night vision goggles. This was evaluated as the greatest Von Mises stress in the eye when the airbag is deployed. The worst-case position was achieved by minimizing the distance between the eyes and goggles, having the occupant look directly into the airbag, and making initial contact with the airbag halfway through its full deployment. By removing the extraocular muscles, the stress sustained by the eye decreased. Simulations with both the goggles remaining fastened and breaking away from the aviator helmet were performed. Finally, placing a protective lens in front of the eyes was found to reduce the stress to the eye but increase the force experienced by the surrounding orbital bones. The finite element model of the eye proved effective at evaluating the experimental boundary conditions, and could be used in the future to evaluate impact loading on eyes that have been surgically corrected and to model the geometry of the orbital bones. / Master of Science

Yes / Physical interactions between objects, or between an object and the ground, are amongst the most biologically relevant for live beings. Prior knowledge of Newtonian physics may play a role in disambiguating an object’s movement as well as foveation by increasing the spatial resolution of the visual input. Observers were shown a virtual 3D scene, representing an ambiguously rotating ball translating on the ground. The ball was perceived as rotating congruently with friction, but only when gaze was located at the point of contact. Inverting or even removing the visual context had little influence on congruent judgements compared with the effect of gaze. Counterintuitively, gaze at the point of contact determines the solution of perceptual ambiguity, but independently of visual context. We suggest this constitutes a frugal strategy, by which the brain infers dynamics locally when faced with a foveated input that is ambiguous. / J.S. was funded by a College of Life Sciences studentship from the University of Leicester.

Syftet med denna studie är att undersöka vilken information om matematiska strategier som går att urskilja ur en persons ögonrörelser vid en undersökning med en enklare typ av eye-tracker. Eye-tracking är en metod som gör det möjligt att studera människors ögonrörelser genom att följa den visuella uppmärksamheten utifrån vart en person tittar. I studien används en stationär eye-tracker för att kunna mäta ögonrörelserna. I den här studien har eye-tracking-undersökningar genomförts med två deltagare som tittar på och löser matematiska uppgifter som kräver prioritering. Den här studien använder en billig (kostar cirka 1000 SEK) kommersiell eye-tracker med ett egentillverkat datainsamlingsprogram. Resultatet av studien visade att det gick att utläsa information och baserat på det gick det att tolka att deltagarna verkligen använde sig av prioriteringsreglerna vid uppgifterna. / The aim of this study is to investigate what information can be gathered by studying a person’s eye movements with a simpler kind of eye-tracker device. Eye-tracking is a technique that allows studying eye movements. In this study a stationary eye-tracking device was used to study and measure eye movements. This study is an original eyetracking study, consisting of two participants who solved mathematical problems that require the use of order of operations whilst wearing an eye-tracker device. The device was a relatively cheap (cost around 1000 SEK) commercial eye-tracker with a home-made data acquisition software system. The result of the study is that it is indeed possible to collect and interpret information using an eye-tracker. Based on the results the conclusion can be made that the participants used the order of operations to solve the assignments.