Clinical Neuroanatomy
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
There are two forms of voluntarily controlled eye movement: Visual pursuit, where a specific target is fixed and followed, using parietal gaze centres closely integrated with the adjacent visual cortexThe ability to select a new target and relocate vision to suit, via frontal gaze centres utilizing direct voluntary pyramidal motor pathway mechanisms. Damage in either of these areas will cause a conjugate gaze palsy, but because the range of movement of both eyes is identically affected, there is no diplopia. At brainstem level, the need to integrate eye movements controlled by three different cranial nerve nuclei widely spaced in the brainstem requires complex and extremely rapidly conducting internuclear pathways. The most critical of these is the medial longitudinal fasciculus. Damage in this pathway causes internuclear ophthalmoplegias, with disconjugate gaze palsies. These will always cause diplopia as the eyes then move independently.
Victims and survivors
John C. Gunn, Pamela J. Taylor in Forensic Psychiatry, 2014
EMDR was developed by Shapiro in 1987 to treat victims of traumatic stress (Shapiro, 1989, 1995, 1996, 2002). Despite the name, eye movement is just one of several forms of stimulation which may be used. The total approach incorporates procedures derived from several psychological schools, including psychodynamic, cognitive behavioural, interpersonal, experiential, and body-centred therapies. The aim of treatment for trauma victims goes beyond reduction in anxiety, as EMDR is an information processing therapy. It can therefore deal with images, beliefs, emotions, physical responses, increased awareness and interpersonal systems. A variety of different structured protocols have been developed for various pathologies, and therapeutic procedures should also be customised to the needs of the person needing treatment. During EMDR, the patient’s attention is directed to both past and present experiences whilst at the same time focusing on an external stimulus. S/he is then asked to let the new material which arises become the material which is used in association with the next set of stimuli. This consecutive sequence of attending to the bilateral stimulation and the developing personal associations is repeated numerous times during a single session.
Can Cognitive Theories Help to Understand Motor Dysfunction in Autism Spectrum Disorder?
Elizabeth B. Torres, Caroline Whyatt in Autism, 2017
Eye movements serve to maintain objects of interest on the fovea, the region of the retina that provides the greatest acuity and color detection (Leigh and Zee 2015). Accurate eye movements are essential for on-line regulation of fine and gross motor accuracy, in addition to proprioceptive signals, and also for providing visual feedback to refine movement accuracy over the long term. Saccades are semiballistic eye movements that shift the eye toward an object of interest, while smooth pursuit eye movements help us to track moving objects, while either an object or ourselves (or both) are in motion (Leigh and Zee 2015). These two main types of eye movements help us to plan actions and coordinate our whole-body movements, and give us visual information about our changing environment to enable us to adapt our actions on the fly. There are a number of known visual processing and ocular motor disturbances in ASD that are likely to impact these processes, which include impaired motion detection (Manning et al. 2013; Takarae et al. 2014), inaccurate eye movements (Takarae et al. 2004a, 2004b; Johnson et al. 2012; Schmitt et al. 2014), and inefficient timing of ocular motor with fine motor actions (Crippa et al. 2013).
Eye Tracking as a Marker of Hyperphagia in Prader-Willi Syndrome
Published in Developmental Neuropsychology, 2018
Alexandra P. Key, Elisabeth M. Dykens
This study takes advantage of recent advances in the development of noninvasive and low-cost measures of physiological processes, such as eye movements, as a potential means to directly evaluate food-related interests in persons with PWS. Eye movements are a natural human behavior that does not require extensive training and can be used throughout the lifespan. Indeed, with single stimuli, interpretable eye tracking data have been acquired in infants as young as 6–9 months of age (Key & Stone, 2012; Merin, Young, Ozonoff, & Rogers, 2006), and complex visual displays have been successfully used in studies of children starting at 2 years of age (Sasson, Elison, Turner-Brown, Dichter, & Bodfish, 2011). The low behavioral demands make eye tracking measures optimal for use across levels of intellectual or verbal ability while also circumventing any social desirability confounds. Eye tracking is thus an attractive means to investigate hyperphagia in PWS.
Correlation between Ocular and Vestibular Abnormalities and Convergence Insufficiency in Post-Concussion Syndrome
Published in Neuro-Ophthalmology, 2020
Abdelbaset Suleiman, Brian J. Lithgow, Neda Anssari, Mehrangiz Ashiri, Zahra Moussavi, Behzad Mansouri
Patients with concussion can experience acute and chronic visual and ocular symptoms because of the damage to cortical, subcortical or brainstem visual/ocular pathways.13 Of the four stereotyped eye movements (i.e., saccade, smooth pursuit, vergence, and vestibule-ocular reflex [VOR]) vergence, particularly convergence, is most affected in concussed patients. Despite the fact that convergence insufficiency (CI) seems to be the hallmark of ocular abnormalities in PCS16,19–22, its use in automated and clinical diagnosis of concussion has been underappreciated. For example, the current two commercially available eye-tracking systems for diagnosis of concussion and PCS have used the accuracy of the coordination of the movements of the two eyes together17 or the abnormal smooth pursuit.18 Many concussion clinics are either unaware or unequipped to measure convergence and other eye movement deficits in concussion. Thus, these abnormalities are left unrecognised unless the patients with PCS are examined by the few optometrists, ophthalmologists, or neuro-ophthalmologists who have experience in concussion.
Smooth Pursuit Eye Movements as a Biomarker for Mild Concussion within 7-Days of Injury
Published in Brain Injury, 2021
Melissa Hunfalvay, Nicholas P. Murray, Revathy Mani, Frederick Robert Carrick
Saccades are identified if the velocity of eye movements exceed 30 degree/second and greater than ¼ degree radius dispersion for less than 100 millisecond duration. If the velocity of eye movements is below 30 degree/second, it could be either a fixation or a SPEM. Smooth pursuits are differentiated from fixations by dispersion and time threshold. Fixations are classified if the eye trace is located within ¼ degree radius of dispersion from the tracking target for a minimum duration of 100 ms. However, if eye trace takes less than 100 milliseconds to move beyond ¼ degree radius of target position with a velocity of less than 30 degrees/second, a smooth pursuit is identified. Once eye movements are classified, the saccades, pursuits and fixation eye movements were calculated. These numbers are converted into percentages by using total time spent within the eye movement classification divided by test time then multiplied by 100 as fixation percentage, smooth pursuit percentage and saccade percentage.
Related Knowledge Centers
- Electrochemistry
- Eye Tracking
- Optic Nerve
- Photoreceptor Cell
- Rapid Eye Movement Sleep
- Reflex
- Retina
- Visual Cortex
- Voluntary Action
- Extraocular Muscles