Smart Eye Tracking Sensors Based on Pixel-Level Image Processing Circuits
Iniewski Krzysztof in Integrated Microsystems, 2017
Fixation or visual fixation means maintaining the visual gaze on a location. Humans (and other animals with a fovea) typically alternate saccades and visual fixations. Visual fixation is never perfectly steady: this eye movement occurs involuntarily. The term “fixation” can also be used to refer to the point in time and space of the focus rather than to the act of fixating; a fixation in this sense is the point between any two saccades, during which the eyes are relatively stationary and virtually all visual input occurs. The fixation always lasts at least 100 ms. It is during these fixations that most visual information is acquired and processed. At least three types of small involuntary eye movements commonly occur during the fixations: Flicks are very rapid (perhaps as little as 30 ms apart), involuntary, saccade-like movements of less than 1°; drifts are very small and slow (about 0.1°/s), apparently random motions of the eye; and tremors are tiny (less than 30 arc seconds), high-frequency (30–150 Hz) eye vibrations [13].
Nasopharyngeal Carcinoma in Man
D. V. M. Gerd Reznik, Sherman F. Stinson in Nasal Tumors in Animals and Man, 2017
These symptoms develop as a result of involvement of the cranial nerves and/or orbit which may be affected intracranially or extracranially. The most common symptoms in this group are diplopia and numbness of face,111 which are due to the paralysis of the abducent (Figure 17) and maxillary nerves, respectively. There could be fixation of eye movements with ptosis (total ophthalmoplegia) due to loss of function of Illrd, IVth, and Vlth cranial nerves (Figure 18). The next most frequently affected nerves are the IXth, Xth, Xlth, and Xllth cranial nerves and the sympathetic trunk, giving rise to complaints like dysphagia, altered speech, and hoarseness of voice. While the Vllth and Vlllth cranial nerves are involved very late in disease, the infiltration of the 1st and Und cranial nerves are very rare. Proptosis, a very uncommon symptom in NPC, is due to invasion of the orbit by the tumor extracranially.
Visual impairments
Michael Horvat, Ronald V. Croce, Caterina Pesce, Ashley Fallaize in Developmental and Adapted Physical Education, 2019
In addition to visual acuity, vision undergoes a developmental process that allows the child to use vision for reading as well as using visual information for learning. In the newborn, the muscles of the eye are weak, and vision is limited to focusing on near objects and responses to light. It could be said that we are born with sight but not vision. Vision will develop from several functions of the eye. For example, visual acuity is the ability to see objects clearly, as measured by performance on the Snellen test. In addition, the eyes must also demonstrate visual fixation, that is, the ability to gaze directly at an object, and pursuant fixation, by which they follow a moving object. Fixation of an object is pursuit at zero velocity, with the pursuit system correcting for small drifts off target. These movements are slower than the fast saccadic movements (involuntary, abrupt, small movements, such as those made when the eye changes their point of fixation). The slower eye movements go by a variety of names but are most commonly called smooth pursuit or tracking movement. The brain must allow the ability to process information and slowly track the object.
Preliminary investigation of visual attention to complex AAC visual scene displays in individuals with and without developmental disabilities
Published in Augmentative and Alternative Communication, 2019
Tara O’Neill, Krista M. Wilkinson, Janice Light
Data were collected using a 17-inch (43.8 cm) Tobii T60 research eye tracker1 that recorded point of eye gaze. The technology projected infrared light from a strip at the top of the Tobii monitor onto the pupils and corneas of participants. Light that reflected off the eyes was recorded by three cameras embedded in a strip at the bottom of the monitor. The T60 monitor was connected to a laptop that controlled the presentation of the stimuli and the acquisition of data using Tobii Studio software2. The input (samples) from the T60 monitor was recorded as a series of x–y-coordinates at a sampling rate of 60 samples/s. A fixation was defined as a sequence of consecutive fixations with gaze within a 35-pixel area for more than 100 ms, calculated automatically by the software using participant distance, pupil location, and angle of the eyeball. A threshold of 100 ms reveals information about visual attention without contamination from blinks, saccades, and other non-fixation behaviours (Manor & Gordon, 2003). This threshold has been used in other research of individuals with developmental disabilities (e.g., Liang & Wilkinson, 2018; Wilkinson & Light, 2014).
Fellow Eye Deficits in Amblyopia
Published in Journal of Binocular Vision and Ocular Motility, 2019
Eileen E. Birch, Krista R. Kelly, Deborah E. Giaschi
During normal fixation, the eyes constantly make small, involuntary movements such as microsaccades, slow drifts, and tremors that aid in maintaining fixation and that prevent image fading.8–11 Remarkably, binocularity in the normal visual system is not affected by these eye movements. When these involuntary eye movements become excessive, instability occurs in the ability to maintain fixation and visual function is disrupted. Fixation instability is a common consequence of strabismus, anisometropia, and amblyopia. Instability associated with these pediatric eye conditions is typically composed of abnormal fixational saccades, ocular drift, and fusion maldevelopment nystagmus.1,4,8,9,12–16 Although amblyopia is associated with larger fixation instability, amblyopia is not a necessary condition for instability as it is also found in nonamblyopic strabismus.1–6,13,17
Future clinical applicability of optical coherence tomography angiography
Published in Clinical and Experimental Optometry, 2019
Jacqueline Chua, Bingyao Tan, Marcus Ang, Monisha E Nongpiur, Anna Cs Tan, Raymond P Najjar, Dan Milea, Leopold Schmetterer
Motion artefacts are lateral displacements of the image, leading to misalignment of the vessels on the OCT‐A image (Figure 1D). These are commonly caused by involuntary eye movements and cardiac motion, often unavoidable during OCT‐A imaging. Bulk motion affects the single B‐scan vascular extraction as well as the quality of en face angiogram. The introduction of an inbuilt eye tracker has significantly reduced excessive motion artefacts and preserved the quality of the angiogram. However, small‐scale motion compensation remains a challenge and can be seen as a single solid line, dual vessel, or vessel discontinuity on the en face angiogram. Furthermore, patients who have ocular pathologies tend to have poor fixation, resulting in excessive eye motions.2015 For such cases, the eye tracker will prolong image acquisition time and may even increase the artefacts due to small‐scale motion.
Related Knowledge Centers
- Eye
- Eye Movement
- Fovea Centralis
- Nervous System
- Retina
- Saccade
- Smooth Pursuit
- Visual Perception
- Neural Substrate
- Stabilized Images