Ernesto Suaste

High Velocity Videoculography to Determination of the Pupil Dynamics

The characterization and determination of the dynamics pupillary in normal subjects, we can help to more accurately determine the behavior of the pupil; the videoculography is a tool that allows us to study the eye and especially the pupil to 30 frames per second in traditional form with the videoculography at high speed allows us to discuss our case in the pupil at 928 frames per second, this speed can determine with greater accuracy and precision dynamics eye, analyzing the movement pupillary each 1 ms approximately. This work shows the results of the capture and escape pupillary through this methodology, the results more accurately taking the capture of images between 5 and 7 ms about using a pulse with duration of 200 ms stimulation [2, 3, 4, 5, 6, 7].

Video‐Oculography To Obtain Pupillary Responses In the Visible Spectrum

Pupillary response (PR) of 20 healthy subjects (3 women and 17 men), was assessed using a chromatic stimulus in a visible spectrum (400–650 nm). The method consists in displaying two chromatics normalized software on a PC monitor under photopic conditions. The luminance of the PC monitor is calibrated with a photometer. This PC monitor was placed at 30 cm from the eye of the subject, while the subject watches it, the consensual reflex is recorded with a video‐oculography system (VOG). This system is based on a video camera operated in night shoot function. The first software displays during 6 seconds a stimulus of a specific wavelength of the continuous range of spectral colors (the visible spectrum), spaced of 10 by 10 nm, beginning at 410 and ending at 660 nm. The second test, displays the same wavelength, but beginning at 400 and ending at 650, and present a black stimulus of 12 seconds of duration, between color stimulus. Once obtained the PR to each specific wavelength, we process the images and we o...

Automated clinical perimeter-based TV pupillometer

We describe the design and building of an apparatus which can be used to measure the central and peripheric visual fields of humans. It minimizes technician mistakes or subjective responses of the patient.

Methodology to Determinate Pupillary Responses Based in High Speed Videoculography in Clinical Eye Applications

The aim of this article is to present the application of high speed videoculography as a tool during the development of a methodology to employ in the ocular clinic diagnostic. It shows exist a significant statistically difference between groups in the time to maximum contraction velocity. And it does not exit a significant statistically difference in the latency and the maximum contraction velocity.

First Approach for Modeling Chromatic Pupillary Responses

Pupillary diameters were obtained of 16 subjects with normal vision of colors. These were stimulated by 26 different chromatic stimuli, which include the visible spectrum from 400 to 650 nm. Based on his pupillary diameter of white color and the chromatic composition of the stimuli, the first approach of the pupillary changes due to the colors is proposed. This paper is focused on the determination objective and quantitative of the chromatic perception of the human being, based on his pupillary response

Piezoelectric ceramics PLZT with Pt implants as unconventional filter, applied in isolation ECG.

This work reports the development through the method of solid state reaction or oxide-mixing technique of PLZT ferroelectric ceramic with implant platinum (Pt) as an unconventional device and their characterization by electrical signals as high pass filters and pass band filter, with application in isolated ECG.

Appropriation of biomedical instruments within the electrophysiologistcardiologist framework

This research aims at analyzing and documenting ways in which a set (four) of cardiologists specialized in electrophysiology get involved in a series of activities that lead them to transform an electronic instrument in a problem-solving tool. We argue that during the appropriation process of the tool, cardiologists develop cognitive schemas as a result of interacting within a community of practice formed by experts, technicians, nurses, and biomedical engineers that allow them to transform an instrument in a problem solving tool.

Measurement of the pupillary response using high-velocity videoculography and conventional videoculography

The study of eye movements is an important technique to identify and evaluate disorders. For a complete understanding of the consequences of eye movements is necessary to measure the horizontal movements, vertical movements and torsional components. Regarding the biodynamics of the pupil and iris, it is required to quantify the functional variations in its expansion and contraction as well as the shapes and contours, due to natural and evoked visual stimulation. Conventional methods of oculography such as electro-oculography or photo-electro-oculography are complex, time consuming, and their accuracy is not appropriate. This is why videooculography is preferred since it is a non-invasive method to record eye movements and components. Video recordings can be done at a studio and can be analyzed later. One of the earliest tests to monitor and evaluate the pupillary changes was the technique of direct observation using lenses and scales. The photographic technique used by Lowenstein and Loewenfeld used infrared light-sensitive film at a rate of 10–50 frames per second, which was manually analyzed to measure the pupil. The technique based on video obtains images of the pupil to analyze the dynamic pupillary changes based on reflective differences between the iris and the pupil. This technique has recently been used in clinical situations with a video camera of CCD or CMOS technology for detecting and observing the slow movements of the eye. At 250 frames per second the results of the velocity of nystagmus are different from those recorded with traditional cameras. HS-VOG (High Speed Video Oculography) demonstrates that conventional low-speed VOG (30 frames per second) is not sufficient to detect the complete bandwidth of eye biomechanics. The HS-VOG approach allows study and analysis of the dynamic behavior of the eye, with the aim of influencing neuro ophthalmologic diagnosis and the development of new methodologies.

Active electronic model for saccadic eye movements

Based on the mechanical model of reciprocal innervation of horizontal eye movements, we propose the design, development and construction of an active-electro model (AEM) to emulate the biodynamics of the human eye from neurological activation in the lateral and medial extraocular muscles. The AEM design characteristics provide mechanical properties such as viscosity, inertia and elasticity of the ocular plant. The model includes together with these features a voltage-controlled resistor (VCR), to maintain the nonlinearity of the plant. These active elements together with passive components form the structure of the extraocular muscles, eyeball and surrounding tissues in the orbital cavity. Characteristics of agonist-antagonist activation is generated by two controlled voltage sources in order to adequately reproduce the neurological activity that generates saccadic movements and thus produces a voltage signal proportional to the speed of the eye. This signal can also provide information about the acceleration and position in order to validate the AEM. Because of this feature to emulate saccadic movements, the AEM is able to reproduce the involuntary eye movements caused by conditions such as horizontal nystagmus. Finally, some advantages of AEM are in the rapid response and ease of obtaining the records of the dynamics of the eyeball movement in evoked responses and applicability to biomedical fields as well as neuroophthalmologists, ophthalmologists and optometrists.

Modeling Chromatic Pupillary Responses in Healthy People

We propose a model to determinate pupillary changes due to chromatic stimulus. The pupillary diameters (PD) from 44 subjects with normal vision of colors were measured. These PD were elicited by 26 different chromatic stimuli (from 400 to 650 nm). The proposed model establishes the pupillary behavior for different colors. To determinate this model, we consider the characteristics of the subject (age and gender), stimulus (luminance and wavelength) as the diameter of their pupil (for white stimulus). With our approach the maximum coefficient of correlation obtained was of 1.0 in 90% of the cases analyzed (PD measured and calculated). This proposed model is the first all over the world.