Natural Eye Research Articles

Refinement of Spatial Receptive Fields in the Developing Mouse Lateral Geniculate Nucleus Is Coordinated with Excitatory and Inhibitory Remodeling.

Receptive field properties of individual visual neurons are dictated by the precise patterns of synaptic connections they receive, including the arrangement of inputs in visual space and features such as polarity (On vs Off). The inputs from the retina to the lateral geniculate nucleus (LGN) in the mouse undergo significant refinement during development. However, it is unknown how this refinement corresponds to the establishment of functional visual response properties. Here we conducted in vivo and in vitro recordings in the mouse LGN, beginning just after natural eye opening, to determine how receptive fields develop as excitatory and feedforward inhibitory retinal afferents refine. Experiments used both male and female subjects. For in vivo assessment of receptive fields, we performed multisite extracellular recordings in awake mice. Spatial receptive fields at eye-opening were >2 times larger than in adulthood, and decreased in size over the subsequent week. This topographic refinement was accompanied by other spatial changes, such as a decrease in spot size preference and an increase in surround suppression. Notably, the degree of specificity in terms of On/Off and sustained/transient responses appeared to be established already at eye opening and did not change. We performed in vitro recordings of the synaptic responses evoked by optic tract stimulation across the same time period. These recordings revealed a pairing of decreased excitatory and increased feedforward inhibitory convergence, providing a potential mechanism to explain the spatial receptive field refinement.SIGNIFICANCE STATEMENT The development of precise patterns of retinogeniculate connectivity has been a powerful model system for understanding the mechanisms underlying the activity-dependent refinement of sensory systems. Here we link the maturation of spatial receptive field properties in the lateral geniculate nucleus (LGN) to the remodeling of retinal and inhibitory feedforward convergence onto LGN neurons. These findings should thus provide a starting point for testing the cell type-specific plasticity mechanisms that lead to refinement of different excitatory and inhibitory inputs, and for determining the effect of these mechanisms on the establishment of mature receptive fields in the LGN.

Detecting fake iris in iris bio-metric system

Iris recognition is an automated method of biometric identification that uses mathematical pattern-recognition techniques on video images of the irises of an individual's eyes, whose complex random patterns are unique and can be seen from some distance. Now days, Iris is being used widely by several organizations, including governments, for identification and authentication purposes. Aadhar, India's UID project uses Iris scan along with fingerprints to uniquely identify people and allocate a Unique Identification Number. Most of the work done in the area of Iris pattern recognition systems emphasizes only on matching of the patterns with the stored templates. Security aspects of the system are still unexplored. The available security algorithms provide only some cryptographic solutions that keeps the template database in a secret cryptographic form. We successfully enhanced the detection of fake iris images and add the provision of detection of false of scanned iris images as template. This enhanced significantly the performance of the system in terms of security and reliability. We use Flash and motion detection of natural eye to detect the liveliness of real iris images before matching from stored templates.

Lowering minimum eye height to increase peak knee and hip flexion during landing

ABSTRACTThe purpose was to determine the effect of lowering minimum eye height through an externally focused object on knee and hip flexion and impact forces during jump-landing. Kinematics and ground reaction forces were collected when 20 male and 19 female participants performed jump-landing trials with their natural minimum eye height, and trials focusing on lowering their minimum eye height to an external object, which was set at 5% or 10% of standing height lower. Participants demonstrated decreased minimum eye height and increased peak knee and hip flexion during early-landing and stance phase when focusing on lowering eye height to the external object (p < 0.01). Peak vertical ground reaction forces during early-landing also decreased for the greater force group (p < 0.001). Jump-landing training through manipulating eye height provides a strategy that involves an external focus and intrinsic feedback, which may have advantages in promoting learning and practical application.

Concerns of anophthalmic patients—a comparison between cryolite glass and polymethyl methacrylate prosthetic eye wearers

To compare the concerns of experienced cryolite glass and (poly)methyl methacrylate (PMMA) prosthetic eye wearers. One hundred six experienced cryolite glass and 63 experienced PMMA prosthetic eye wearers completed an anonymous questionnaire regarding general and specific prosthetic eye concerns at least 2years after natural eye loss. From these independent anophthalmic populations, we identified 34 case-control pairs matched for the known influencing demographic variables of gender, occupation, age, and time since natural eye loss. The levels of concern were significantly lower in the cryolite glass group than those in the PMMA group for the following: loss of balance (p < 0.001), phantom sight vision (p < 0.001), pain (p < 0.001), receiving good advice (p = 0.001), fullness of orbit (p = 0.001), size (p = 0.007), direction of gaze relative to the healthy fellow eye (p = 0.005), eye lid contour (p = 0.037), comfort of the prosthetic eye (p < 0.001), colour relative to the healthy fellow eye (p < 0.001), and retention of the prosthetic eye (p < 0.001). Concerns about watering, crusting, discharge, visual perception, appearance, movement of the prosthetic eye, and health of the remaining eye were not significantly different between both groups. The results of this study showed that many general and specific levels of concern were significantly lower for cryolite glass prosthetic eye wearers than for PMMA prosthetic eye wearers. The question of why there are significant differences and to what extent the material of the prosthesis (cryolite glass or PMMA) has an impact on various concerns remains unanswered and should be addressed in a prospective comparative multicentre trial.

Excitatory Pathways from the Lateral Habenula Enable Propofol-Induced Sedation

SummaryThe lateral habenula has been widely studied for its contribution in generating reward-related behaviors [1, 2]. We have found that this nucleus plays an unexpected role in the sedative actions of the general anesthetic propofol. The lateral habenula is a glutamatergic, excitatory hub that projects to multiple targets throughout the brain, including GABAergic and aminergic nuclei that control arousal [3, 4, 5]. When glutamate release from the lateral habenula in mice was genetically blocked, the ability of propofol to induce sedation was greatly diminished. In addition to this reduced sensitivity to propofol, blocking output from the lateral habenula caused natural non-rapid eye movement (NREM) sleep to become highly fragmented, especially during the rest (“lights on”) period. This fragmentation was largely reversed by the dual orexinergic antagonist almorexant. We conclude that the glutamatergic output from the lateral habenula is permissive for the sedative actions of propofol and is also necessary for the consolidation of natural sleep.

Health status by gender, hair color, and eye color: Red-haired women are the most divergent.

Red hair is associated in women with pain sensitivity. This medical condition, and perhaps others, seems facilitated by the combination of being red-haired and female. We tested this hypothesis by questioning a large sample of Czech and Slovak respondents about the natural redness and darkness of their hair, their natural eye color, their physical and mental health (24 categories), and other personal attributes (height, weight, number of children, lifelong number of sexual partners, frequency of smoking). Red-haired women did worse than other women in ten health categories and better in only three, being particularly prone to colorectal, cervical, uterine, and ovarian cancer. Red-haired men showed a balanced pattern, doing better than other men in three health categories and worse in three. Number of children was the only category where both male and female redheads did better than other respondents. We also confirmed earlier findings that red hair is naturally more frequent in women than in men. Of the ‘new’ hair and eye colors, red hair diverges the most from the ancestral state of black hair and brown eyes, being the most sexually dimorphic variant not only in population frequency but also in health status. This divergent health status may have one or more causes: direct effects of red hair pigments (pheomelanins) or their by-products; effects of other genes that show linkage with genes involved in pheomelanin production; excessive prenatal exposure to estrogen (which facilitates expression of red hair during fetal development and which, at high levels, may cause health problems later in life); evolutionary recentness of red hair and corresponding lack of time to correct negative side effects; or genetic incompatibilities associated with the allele Val92Met, which seems to be of Neanderthal origin and is one of the alleles that can cause red hair.

Effect of Oil Paint Addition on Porosity of Scleral Part of Acrylic Ocular Prosthesis

Background: white acrylic resins are widely used for fabrication of scleral part of ocular prostheses to restore acquired or congeni- tal ocular defects. However, such materials are not available in the local markets. Several additive materials, hence, must be applied to the prosthesis to match the colour of natural eye. The aim of this study was to assess the effect of adding titanium dioxide oil paints to scleral part of ocular prosthesis on its porosity. Methods: there were 20 samples in total. The first group was fabricated without addition of oil paint and considered as control. The second group was constructed from heat cured acrylic resin with addition of oil paint in a concentration of 1 ml. A surface area of 1cm 2 was limited in the center of each specimen &observed under optical microscopy and numbers of pores per area was manually determined. All values were analyzed using SPSS version 20 and comparison between 2 groups was obtained using inde- pendent t test. Results: there was an increase in the mean values of porosity following addition of oil paint. The control group presented a lower mean value of porosity compared to experimental group. however, no significant differences between control and TiO 2 group where P >0.05. Conclusion: the incorporation of titanium dioxide into clear acrylic resin increases its ' porosity .

Volumetric integration model of the Stiles-Crawford effect of the first kind and its experimental verification.

The integrated Stiles-Crawford function is commonly used as apodization model for vision through the natural eye pupil. However, this method does not account for possible effects related to the retinal thickness, the large length-to-diameter aspect ratio of the photoreceptors, or the use of nonMaxwellian illumination. Here, we introduce a geometrical optics model to calculate the fraction of overlap between light at the retina and the photoreceptor outer segments where absorption triggers vision. The model, which does not account for photoreceptor waveguiding, is discussed for both Maxwellian and nonMaxwellian illumination. The integrated Stiles-Crawford effect is analyzed experimentally with a uniaxial pupil-size flicker methodology and we find that the psychophysical measurements match better to the geometrical optics predictions than direct integration of a Stiles-Crawford function.

Alternative Technique of Iris Orientation in a Custom-Made Ocular Prosthesis.

Accurate positioning of the iris is critical for the success of an ocular prosthesis. Precise duplication of size and location of the iris is essential for the establishment of realism, symmetry, and a natural-appearing gaze. This article explores an alternative procedure for positioning the iris in a custom-made ocular prosthesis using a pupillary distance ruler (PD ruler). The orientation and mediolateral dimension of the iris of the natural eye was measured from the graduated scale on a PD ruler and transferred on to the sculpted scleral wax pattern. The iris button was positioned in the marked area, and the established orientation was evaluated for symmetry and a natural-appearing gaze. Accurate, predictable, and easy positioning of the iris with the transfer of these dimensions to the definitive prosthesis provided a good result in terms of patient esthetics and satisfaction.

Gaze-in-World movement Classification for Unconstrained Head Motion during Natural Tasks.

Accurate classification of eye movements is an integral component of many psychophysical experiments. Most event classifiers are restricted to the analysis of eye-in-head (EIHv) vectors while the head is fixed, and detect two classes of gaze events, namely fixations and saccades. Classification of eye movements as Vestibular Ocular reflex (VOR) or Smooth pursuits (SP) require that we compensate gaze motion with a person's head movements. As the complexity of naturalistic behavioral paradigms increases, so does the need for gaze classification with head-free motion which could detect these complex eye movements. We propose the use of a supervised Machine Learning (ML) classifier for the automated analysis of head free gaze signal. As a preliminary test, we used a SVM classifier to label a 60 Hz test dataset from a virtual reality ball catching task into periods of fixations, saccades and pursuit. This preliminary test resulted in 94% accuracy in a sample to sample comparison with an artificially generated set of gaze movements reflective of measured gaze statistics, and visual inspection shows very high correspondence to subjective analysis of the gaze signal. This promising methodology has since been extended to the analysis of data collected during natural tasks. Five subjects' head and gaze movements were recorded using an IMU and a 120 Hz SMI Wireless ETG2 as they performed four different natural tasks for 10 minutes each. This yielded 120 minutes of angular velocity data of the gaze in world vector (GIWv) during natural tasks. Four experts manually annotated a subset of the data as periods of fixation, saccade, smooth pursuit, and blinks. Inter-labeler reliability was measured to generate a confidence metric and a cost function for misclassifications. We summarize the statistics of natural eye movements and compare various ML based temporal series classification schemes. Meeting abstract presented at VSS 2017

Survey of Ocular Prosthetics Rehabilitation in the United Kingdom, Part 1: Anophthalmic Patients' Aetiology, Opinions, and Attitudes.

Ocular prostheses are constructed to aid cosmetic, functional, and psychological rehabilitation of anophthalmic patients. Part-1 of this study aimed to evaluate anophthalmic patients' opinions, attitudes, and experience about aspects related to their postfit ocular prostheses. One hundred sixty questionnaires were delivered to anophthalmic patients inquiring about different information such as age, gender, occupation, eye-loss cause, prosthesis type, prosthesis-wearing frequency, prosthesis-cleaning frequency, and problems encountered. A total of 126 questionnaires were returned (response rate was 78.8%). Data was analyzed using SPSS software (P <0.05). The patients were 74 males and 52 females (57.55 years ± 17.57). Almost 50% of the patients lost their eye due to trauma that was the highest among other causes (P <0.05). High proportion clean their prosthesis daily (37.4%) which was the highest among other cleaning regimes (P <0.05). Almost 30.3% experienced having problems with their prosthetic eye. Patients who clean their prosthetic eye every 6 months have experienced more problems (P <0.05). Majority of patients wear their prosthetic eyes 24 hours (92%) (P <0.05). Half of patients who received a prosthetic eye for the first time experienced problems with it (P <0.05) such as excess discharge (45%), infection (25%), and soreness (20%). However, the problems were independent of prosthesis-type (P >0.05). Trauma is the most common cause of anophthalmic patients in the North-West of England. Anophthalmic patients are likely to experience problems with their prosthetic eye if they have lost their natural eye due to disease; it is their first prosthesis; or if they clean it once every 6 months.

Modern Speed-Reading Apps Do Not Foster Reading Comprehension.

New computer apps are gaining popularity by suggesting that reading speeds can be drastically increased when eye movements that normally occur during reading are eliminated. This is done using rapid serial visual presentation (RSVP), where words are presented 1 at a time, thus preventing natural eye movements such as saccades, fixations, and regressions from occurring. Al- though the companies producing these apps suggest that RSVP reading does not yield comprehension deficits, research investigating the role of eye movements in reading documents shows the necessity of natural eye movements for accurate comprehension. The current study explored variables that may affect reading comprehension during RSVP reading, including text difficulty (6th grade and 12th grade), text presentation speed (static, 700 wpm, and 1,000 wpm), and working memory capacity (WMC). Consistent with recent work showing a tenuous relationship between comprehension and WMC, participants' WMC did not predict comprehension scores. Instead, comprehension was most affected by reading speed: Static text was associated with superior performance, relative to either RSVP reading condition. Furthermore, slower RSVP speeds yielded better verbatim comprehension, and faster speeds benefited inferential comprehension.

Focus and perspective adaptive digital surgical microscope: optomechanical design and experimental implementation.

This paper relates to the improvement of conventional surgical stereo microscopy via the application of digital recording devices and adaptive optics. The research is aimed at improving the working conditions of the surgeon during the operation, such that free head movement is possible. The depth clues known from conventional stereo microscopy in interaction with the human eye’s functionality, such as convergence, disparity, angular elevation, parallax, and accommodation, are implemented in a digital recording system via adaptive optomechanical components. Two laterally moving pupil apertures have been used mimicking the digital implementation of the eye’s vergence and head motion. The natural eye’s accommodation is mimicked via the application of a tunable lens. Additionally, another system has been built, which enables tracking the surgeon’s eye pupil through a digital displaying stereoscopic microscope to supply the necessary information for steering the recording system. The optomechanical design and experimental results for both systems, digital recording stereoscopic microscope and pupil tracking system, are shown.

An iris positioning device and centering approach: A technique

For patients who have lost an eye as result of trauma or a carcinoma, accurate replacement with an ocular prosthesis that is symmetrical to the natural eye is essential. This report describes a technique for recording the measurement and position of the iris of the natural eye and accurately transferring it to the prosthetic eye of the patient. The technique is both straightforward and accurate.

Matching the Iris Color of Ocular Prosthesis Using an Eye Contact Lens: New Technique

The prosthodontist can give a cosmetically acceptable ocular prosthesis for those patients undergoing surgical resection of the eye ball. This artificial replacement being either stock or custom made. A favourable esthetics results could be achieved by select- ing tinted contact lenses to match the iris color of the ocular prosthesis with natural eye color. The design, size, contour, technique and multi-color contact eye lenses facilitate the production of a satisfactory prosthesis.

Wet laboratory training using porcine eyes with eyelids

ObjectiveThis study aimed to evaluate the usefulness of a new wet laboratory (wet lab) system using porcine eyes with eyelids. DesignTeaching device trial. ParticipantsPorcine eyes with orbital tissues and eyelids. MethodsTwenty porcine eyes with orbital tissues and eyelids were enucleated from pigs butchered at age 6 months. These eyes were positioned in the eye sockets of a model head and stabilized with a pin. Eye draping, dressing with tape, and speculum placement were conducted. The vertical and horizontal widths of the palpebra under the speculum setting were compared with those of 55 patients who underwent cataract surgery. The rotation and torsion of the porcine eye in the new wet lab system were also compared with those of a conventional wet lab system. For comparison with actual cataract surgery, 5 ophthalmologists, including residents, were asked to respond to a questionnaire survey. ResultsThe horizontal widths of the palpebra under the speculum setting were 27.5 ± 3.1 mm in porcine eyes and 28.6 ± 5.1 mm in human eyes, and the vertical widths were 16.9 ± 1.3 mm and 16.1 ± 1.5 mm (p = 0.53, 0.05). The amounts of rotation and torsion were significantly greater with the new wet lab system. Ophthalmologists evaluated the new wet lab system as being more realistic than the conventional system, in terms of both natural eye movement and restriction of the surgical field by the eyelid and the speculum. ConclusionsWet lab training using porcine eyes with eyelids is more practical than older systems as it reproduces an ocular surgical field very similar to that of humans.

Webcam-Based Eye Movement Analysis Using CNN

Due to its low price, webcam has become one of the most promising sensors with the rapid development of computer vision. However, the accuracies of eye tracking and eye movement analysis are largely limited by the quality of the webcam videos. To solve this issue, a novel eye movement analysis model is proposed based on five eye feature points rather than a single point (such as the iris center). First, a single convolutional neural network (CNN) is trained for eye feature point detection, and five eye feature points are detected for obtaining more useful eye movement information. Subsequently, six types of original time-varying eye movement signals can be constructed by feature points of each frame, which can reduce the dependency of the iris center in low quality videos. Finally, behaviors-CNN can be trained by the time-varying eye movement signals for recognizing different eye movement patterns, which is capable of avoiding the influence of errors from the basic eye movement type detection and artificial eye movement feature construction. To validate the performance, a webcam-based visual activity data set was constructed, which contained almost 0.5 million frames collected from 38 subjects. The experimental results on this database have demonstrated that the proposed model can obtain promising results for natural and convenient eye movement-based applications.

Customizing the Stock Acrylic Resin Ocular Prosthesis: Simplified and Innovative Technique – A Case Report

Eyes are the most precious gift given to us by the God as they help us to enjoy the beautiful world around us. Loss of the eyes can be detrimental to the patient both physically as well as mentally. Therefore, prosthodontic rehabilitation of such patients should be done as soon as possible with the ocular prosthesis. An ocular prosthesis, artificial eye or glass eye is a type of craniofacial prosthesis that replaces an absent natural eye following an enucleation, evisceration, or orbital exenteration. This article describes the simplified and innovative technique of prosthetic rehabilitation of a patient by customizing the stock eyes available in the market.

Evaluation of the Tobii EyeX Eye tracking controller and Matlab toolkit for research

The Tobii Eyex Controller is a new low-cost binocular eye tracker marketed for integration in gaming and consumer applications. The manufacturers claim that the system was conceived for natural eye gaze interaction, does not require continuous recalibration, and allows moderate head movements. The Controller is provided with a SDK to foster the development of new eye tracking applications. We review the characteristics of the device for its possible use in scientific research. We develop and evaluate an open source Matlab Toolkit that can be employed to interface with the EyeX device for gaze recording in behavioral experiments. The Toolkit provides calibration procedures tailored to both binocular and monocular experiments, as well as procedures to evaluate other eye tracking devices. The observed performance of the EyeX (i.e. accuracy < 0.6°, precision < 0.25°, latency < 50 ms and sampling frequency ≈55 Hz), is sufficient for some classes of research application. The device can be successfully employed to measure fixation parameters, saccadic, smooth pursuit and vergence eye movements. However, the relatively low sampling rate and moderate precision limit the suitability of the EyeX for monitoring micro-saccadic eye movements or for real-time gaze-contingent stimulus control. For these applications, research grade, high-cost eye tracking technology may still be necessary. Therefore, despite its limitations with respect to high-end devices, the EyeX has the potential to further the dissemination of eye tracking technology to a broad audience, and could be a valuable asset in consumer and gaming applications as well as a subset of basic and clinical research settings.

Model-based stability assessment of ventilatory control in overweight adolescents with obstructive sleep apnea during NREM sleep.

Obstructive sleep apnea (OSA) involves the interplay of several different factors such as an unfavorable upper airway anatomy, deficiencies in pharyngeal muscle responsiveness, a low arousal threshold, and ventilatory control instability. Although the stability of ventilatory control has been extensively studied in adults, little is known about its characteristics in the pediatric population. In this study, we developed a novel experimental setup that allowed us to perturb the respiratory system during natural non-rapid eye movement (NREM) sleep conditions by manipulating the inspiratory pressure, provided by a bilevel pressure ventilator, to induce sighs after upper airway stabilization. Furthermore, we present a modeling framework that utilizes the noninvasively measured ventilatory responses to the induced sighs and spontaneous breathing data to obtain representations of the processes involved in the chemical regulation of respiration and extract their stability characteristics. After validation with simulated data, the modeling technique was applied to data collected experimentally from 11 OSA and 15 non-OSA overweight adolescents. Statistical analysis of the model-derived stability parameters revealed a significantly higher plant gain and lower controller gain in the OSA group (P = 0.046 and P = 0.007, respectively); however, no differences were found in loop gain (LG) and circulatory time delay between the groups. OSA severity and LG, within the 0.03-0.04-Hz frequency band, were significantly negatively associated (r = -0.434, P = 0.026). Contrary to what has been found in adults, our results suggest that in overweight adolescents, OSA is unlikely to be initiated through ventilatory instability resulting from elevated chemical loop gain.