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[ES] La Óptica Oftálmica es una materia que se encuentra dentro del Plan de Estudios del Grado en Óptica y Optometría, dentro del módulo de Óptica se encuentra la materia Óptica Oftálmica. A grandes rasgos, en Óptica Oftálmica se estudia el proceso de formación de imágenes y propiedades de todo tipo de lente oftálmica utilizada en prescripciones optométricas y su proceso de adaptación. Asimismo, trata las técnicas de centrado, adaptación, montaje y manipulación de todo tipo de lentes, de una prescripción optométrica, ayuda visual y gafa de protección. La metodología docente empleada en la asignatura se basa, por un lado, en una parte presencial que incluye las modalidades de clase teórica, prácticas de problemas y clases prácticas, y, por otro lado, una parte no presencial que potencia el autoaprendizaje y que incluye las modalidades de tutorías no presenciales, estudio y trabajo en grupo e individual. Las prácticas de laboratorio se realizan en el laboratorio habilitado para la asignatura. Su contenido aparece agrupado en 8 prácticas individuales de 2 horas de duración por práctica en las que se realiza la medida y montaje de todos los elementos compensadores estudiados en la asignatura. Para cada práctica se prepara un guion donde se indica su objetivo, el material y el procedimiento a seguir. Se propone elaborar videotutoriales con las técnicas de medida de potencias de lentes oftálmicas que proporcionarán al estudiante del Grado de Óptica y Optometría la posibilidad de consultar y visionar en cualquier lugar y momento el manejo del instrumental utilizado en el laboratorio de Óptica Oftálmica. Estas herramientas, además, facilitarán la labor docente del profesorado haciéndola más eficiente al aprovechar los medios tecnológicos que dispone.

The evaluation of eye blinking has been used for the diagnosis of neurological disorders and fatigue. Despite the extensive literature, no objective method has been found to analyze its kinematic and dynamic behavior. A non-contact technique based on the high-speed recording of the light reflected by the eyelid in the blinking process and the off-line processing of the sequence is presented. It allows for objectively determining the start and end of a blink, besides obtaining different physical magnitudes: position, speed, eyelid acceleration as well as the power, work and mechanical impulse developed by the muscles involved in the physiological process. The parameters derived from these magnitudes provide a unique set of features that can be used to biometric authentication. This possibility has been tested with a limited number of subjects with a correct identification rate of up to 99.7%, thus showing the potential application of the method.

The file data.mat contains two Matlab’s variables: a 1924x172 matrix, named intensity_blinks, which contains the intensity signals of 1924 blinks from 26 subjects (74 per subject) and a 1924x30 matrix, named subj_vect, with those 1924 blinks characterized by vectors of 29 features.

Purpose. To assess anterior corneal surface stability 12 months following hyperopic LASIK correction with a light propagation algorithm. Setting. Vissum Instituto Oftalmológico de Alicante, Universidad Miguel Hernández, Alicante, Spain. Methods. This retrospective consecutive observational study includes 37 eyes of 37 patients treated with 6th-generation excimer laser platform (Schwind Amaris). Hyperopic LASIK was performed in all of them by the same surgeon (JLA) and completed 12-month follow-up. Corneal topography was analyzed with a light propagation algorithm, to assess the stability of the corneal outcomes along one year of follow-up. Results. Between three and twelve months postoperatively, an objective corneal power (OCP) regression of 0.39 D and 0.41 D was found for 6 mm and 9 mm central corneal zone, respectively. Subjective outcomes at the end of the follow-up period were as follows: 65% of eyes had spherical equivalent within ±0.50 D. 70% of eyes had an uncorrected distance visual acuity 20/20 or better. 86% of eyes had the same or better corrected distance visual acuity. In terms of stability, 0.14 D of regression was found. No statistically significant differences were found for all the study parameters evaluated at different postoperative moments over the 12-month period. Conclusions. Light propagation analysis confirms corneal surface stability following modern hyperopic LASIK with a 6th-generation excimer laser technology over a 12-month period.

1924x30 matrix with 1924 blinks from 26 subjects characterized by vectors of features.

Visualization 1. Sequence of frames with a rhombus that rotated 2 degrees in steps of 0.01 degrees with reference to a point. We the sequence where both segments, the theoretical and the computed intersection point, the rotation centre, the computed bisector and the orientation angle are plotted. Visualization 2. Tracking the position of a rotation object. Visualization 3. Recorded video of the deflection of a steel beam.

El frontofocómetro es un instrumento óptico esencial en la práctica del óptico optometrista utilizado para la medida de potencias de lentes oftálmicas, así como la determinación de su centro óptico y orientación de los meridianos principales en el caso de que la lente sea astigmática. El fundamento del frontofocómetro manual se basa en un test iluminado, un sistema de colimación y uno de observación que incluye un retículo. La potencia de una lente, centro óptico y orientación de los meridianos se determina visualmente a partir de la posición del test que proporciona una imagen nítida. Si sustituimos el observador por una cámara, podemos grabar la técnica de medida para así poder explicarla detalladamente mostrando qué se debe ver y cómo. La aplicación de TIC facilitará la explicación de su uso ya que podrá proyectarse el vídeo para mostrar el proceso en directo a todo el grupo de estudiantes. Además, permitirá la grabación de diferentes vídeos que podrían alojarse online para así estar a disposición del estudiante en cualquier lugar y momento.

We present a method for distance measuring planar displacements and rotations with image processing methods. The method is based on tracking the intersection of two non-parallel straight segments extracted from a scene. This kind of target can be easily identified in civil structures or in industrial elements or machines. Therefore, our method is suitable for measuring the displacement in some parts of structures and therefore for determining their stress state. We have evaluated the accuracy of our proposal through a computational simulation and validated the method through two lab experiments. We obtained a theoretical mean subpixel accuracy of 0.03 px for the position and 0.02 degrees for the orientation, whereas the practical accuracies were 0.1 px and 0.04 degrees, respectively. One presented lab application deals with the tracking of an object attached to a rotation stage motor in order to characterize the dynamic of the stage, and another application is addressed to the noncontact assessment of the bending and torsional process of a steel beam subjected to load. The method is simple, easy to implement, and widely applicable.

Object vibrations and movements can be detected through changes in its luminance. In this paper, we demonstrate that we can obtain the vibration frequency of all vibrating targets in the sequence simultaneously through the analysis of local neighborhoods. The study is completed with a short-time Fourier analysis so that changes in the movement frequencies are also accounted. We also show that this information can be displayed like a color frequency map that can be superimposed to the video sequence providing a whole description of the analyzed sequence. The method can be used to analyze complex structures since their different vibrating parts can be visualized at a glance. The main algorithms, methods and some sequences are freely downloadable so that new applications and procedures can be implemented by the scientific community.

Object vibrations and movements can be detected through changes in its luminance. In this paper, we demonstrate that we can obtain the vibration frequency of all vibrating targets in the sequence simultaneously through the analysis of local neighborhoods. The study is completed with a short-time Fourier analysis so that changes in the movement frequencies are also accounted. We also show that this information can be displayed like a color frequency map that can be superimposed to the video sequence providing a whole description of the analyzed sequence. The method can be used to analyze complex structures since their different vibrating parts can be visualized at a glance. The main algorithms, methods and some sequences are freely downloadable so that new applications and procedures can be implemented by the scientific community.

Object tracking with subpixel accuracy is of fundamental importance in many fields since it provides optimal performance at relatively low-cost. Although there are many theoretical proposals that lead to resolution increments of several orders of magnitude, in practice, this resolution is limited by the imaging systems. In this paper we propose and demonstrate through numerical models a realistic limit for subpixel accuracy. The final result is that maximum achievable resolution enhancement is connected with the dynamic range of the image, i.e. the detection limit is 1/2^(nr.bits). Results here presented may help to proper design of superresolution experiments in microscopy, surveillance, defense and other fields.

Object tracking with subpixel accuracy is of fundamental importance in many fields since it provides optimal performance at relatively low cost. Although there are many theoretical proposals that lead to resolution increments of several orders of magnitude, in practice this resolution is limited by the imaging systems. In this paper we propose and demonstrate through simple numerical models a realistic limit for subpixel accuracy. The final result is that maximum achievable resolution enhancement is connected with the dynamic range of the image, i.e., the detection limit is 1/2∧(nr.bits). The results here presented may aid in proper design of superresolution experiments in microscopy, surveillance, defense, and other fields.

El abaratamiento de los dispositivos basados en CCDs así como el aumento de sus prestaciones (velocidad de proceso y almacenamiento) ha posibilitado la aparición de cámaras de bolsillo capaces de grabar secuencias de vídeo en alta velocidad. A partir de estas secuencias y mediante un procesado sencillo de posible medir la frecuencia de vibración de diferentes objetos presentes en la secuencia e incluso elaborar un mapa de vibraciones.

El desarrollo de un video-oculógrafo binocular con resolución 15 micras y 4 ms orientado a la caracterización de los reflejos pupilares ha revelado la existencia de un movimiento de elevación del globo ocular, conocido como fenómeno de Bell, previo al reflejo pupilar a la luz. Además, su uso para el análisis del reflejo pupilar a la luz ha confirmado que las respuestas pupilares directa y consensual no presentan ninguna diferencia temporal apreciable

We present a purposeful initiative to open new grounds for teaching Geometrical Optics. It is based on the creation of an innovative education networking involving academic staff from three Spanish universities linked together around Optics. Nowadays, students demand online resources such as innovative multimedia tools for complementing the understanding of their studies. Geometrical Optics relies on basics of light phenomena like reflection and refraction and the use of simple optical elements such as mirrors, prisms, lenses, and fibers. The mathematical treatment is simple and the equations are not too complicated. But from our long time experience in teaching to undergraduate students, we realize that important concepts are missed by these students because they do not work ray tracing as they should do. Moreover, Geometrical Optics laboratory is crucial by providing many short Optics experiments and thus stimulating students interest in the study of such a topic. Multimedia applications help teachers to cover those student demands. In that sense, our educational networking shares and develops online materials based on 1) video-tutorials of laboratory experiences and of ray tracing exercises, 2) different online platforms for student self-examinations and 3) computer assisted geometrical optics exercises. That will result in interesting educational synergies and promote student autonomy for learning Optics.

We present a targetless motion tracking method for detecting planar movements with subpixel accuracy. This method is based on the computation and tracking of the intersection of two nonparallel straight-line segments in the image of a moving object in a scene. The method is simple and easy to implement because no complex structures have to be detected. It has been tested and validated using a lab experiment consisting of a vibrating object that was recorded with a high-speed camera working at 1000 fps. We managed to track displacements with an accuracy of hundredths of pixel or even of thousandths of pixel in the case of tracking harmonic vibrations. The method is widely applicable because it can be used for distance measuring amplitude and frequency of vibrations with a vision system.

Subpixel techniques are commonly used to increase the spatial resolution in tracking tasks. Object tracking with targets of known shape permits obtaining information about object position and orientation in the three-dimensional space. A proper selection of the target shape allows us to determine its position inside a plane and its angular and azimuthal orientation under certain limits. Our proposal is demonstrated both numerical and experimentally and provides an increase the accuracy of more than one order of magnitude compared to the nominal resolution of the sensor. The experiment has been performed with a high-speed camera, which simultaneously provides high spatial and temporal resolution, so it may be interesting for some applications where this kind of targets can be attached, such as vibration monitoring and structural analysis.

Cálculo gráfico de la posición del centro óptico de visión de cerca en una bifocal a partir de la posición del centro geométrico de la pastilla adicional, las potencias de los meridianos principales y la adición.

Background: The pupillary light reflex characterizes the direct and consensual response of the eye to the perceived brightness of a stimulus. It has been used as indicator of both neurological and optic nerve pathologies. As with other eye reflexes, this reflex constitutes an almost instantaneous movement and is linked to activation of the same midbrain area. The latency of the pupillary light reflex is around 200 ms, although the literature also indicates that the fastest eye reflexes last 20 ms. Therefore, a system with sufficiently high spatial and temporal resolutions is required for accurate assessment. In this study, we analyzed the pupillary light reflex to determine whether any small discrepancy exists between the direct and consensual responses, and to ascertain whether any other eye reflex occurs before the pupillary light reflex. Methods: We constructed a binocular video-oculography system two high-speed cameras that simultaneously focused on both eyes. This was then employed to assess the direct and consensual responses of each eye using our own algorithm based on Circular Hough Transform to detect and track the pupil. Time parameters describing the pupillary light reflex were obtained from the radius time-variation. Eight healthy subjects (4 women, 4 men, aged 24–45) participated in this experiment. Results: Our system, which has a resolution of 15 microns and 4 ms, obtained time parameters describing the pupillary light reflex that were similar to those reported in previous studies, with no significant differences between direct and consensual reflexes. Moreover, it revealed an incomplete reflex blink and an upward eye movement at around 100 ms that may correspond to Bell’s phenomenon. Conclusions: Direct and consensual pupillary responses do not any significant temporal differences. The system and method described here could prove useful for further assessment of pupillary and blink reflexes. The resolution obtained revealed the existence reported her

Web con aplicación Java para el cálculo gráfico de la posición (en cm) del centro óptico de visión de cerca en una bifocal a partir de la posición del centro geométrico de la pastilla adicional (en cm), las potencias de los meridianos principales y la adición (en D).

The optical power of a thick spherical lens and its Coddington shape factor are essential magnitudes that characterize its image quality. We propose an experimental procedure and apparatus that allow accurate determination of those magnitudes for any spherical lens from geometrical measurements. It overcomes the drawbacks of other devices that need of the refractive index or may damage the lens surfaces, like spherometers, and provides similar results to commercial lensmeters.

Eye response to light exposure is usually described through the pupillary light reflex, which controls the pupil diameter and allows for testing the sensory and motor functions of the eye. We have arranged an experimental setup and developed a procedure in order to improve the video-oculography experiment through high-speed imaging. The technique has been applied over eleven people distinguishing between consensual and direct pupillary light reflexes and analyzing the eye dominance. We found no significant differences. Moreover, obtained time parameters describing the pupil light reflex agree with those from literature.

Behaviour analysis of construction safety systems is of fundamental importance to avoid accidental injuries. Traditionally, measurements of dynamic actions in Civil Engineering have been done through accelerometers, but high-speed cameras and image processing techniques can play an important role in this area. Here, we propose using morphological image filtering and Hough transform on high-speed video sequence as tools for dynamic measurements on that field. The presented method is applied to obtain the trajectory and acceleration of a cylindrical ballast falling from a building and trapped by a thread net. Results show that safety recommendations given in construction codes can be potentially dangerous for workers.

In this paper, we demonstrate the use of a video camera for measuring the frequency of small-amplitude vibration movements. The method is based on image acquisition and multilevel thresholding and it only requires a video camera with high enough acquisition rate, not being necessary the use of targets or auxiliary laser beams. Our proposal is accurate and robust. We demonstrate the technique with a pocket camera recording low-resolution videos with AVI-JPEG compression and measuring different objects that vibrate in parallel or perpendicular direction to the optical sensor. Despite the low resolution and the noise, we are able to measure the main vibration modes of a tuning fork, a loudspeaker and a bridge. Results are successfully compared with design parameters and measurements with alternative devices.

Grabaciones mediante cámara y micrófono de un altavoz emitiendo un sonido formado por 2 funciones sinusoidales de frecuencias 317 Hz y 412 Hz.

Vídeo del experimento realizado para medir la frecuencia de vibración de un diapasón.

Retinal image quality is commonly analyzed through parameters inherited from instrumental optics. These parameters are defined for ‘good optics’ so they are hard to translate into visual quality metrics. Instead of using point or artificial functions, we propose a quality index that takes into account properties of natural images. These images usually show strong local correlations that help to interpret the image. Our aim is to derive an objective index that quantifies the quality of vision by taking into account the local structure of the scene, instead of focusing on a particular aberration. As we show, this index highly correlates with visual acuity and allows inter-comparison of natural images around the retina. The usefulness of the index is proven through the analysis of real eyes before and after undergoing corneal surgery, which usually are hard to analyze with standard metrics.

We present an algorithm to process images of reflected Placido rings captured by a commercial videokeratoscope. Raw data are obtained with no Cartesian-to-polar-coordinate conversion, thus avoiding interpolation and associated numerical artifacts. The method provides a characteristic equation for the device and is able to process around 6 times more corneal data than the commercial software. Our proposal allows complete control over the whole process from the capture of corneal images until the computation of curvature radii.