China
Africa
Explore chapters and articles related to this topic
Clinical Examination in Neuro-Ophthalmology
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Selvakumar Ambika, Krishnakumar Padmalakshmi
Ductions are monocular eye movements. Medial movement of eye is termed as adduction, lateral is—abduction, upward—elevation/supraduction, downward-depression/infraduction. Vergences are binocular eye movements, which may be convergence or divergence. Convergence is tested by asking the patient to look at an accommodative target as it is brought closer to the nose and is associated with physiological constriction of pupils. Disorders of midbrain and Parkinson's disease can cause convergence insufficiency.
Cranial Neuropathies II, III, IV, and VI
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Tanyatuth Padungkiatsagul, Heather E. Moss
The ductions should be tested. Ductions are the movements of both eyes in all the directions of gaze and are tested by asking the patient to look in a direction, follow an object, or localize a sound with their eyes. How the movement is stimulated does not matter as this is a motor test, not a sensory test. Limitations of motility of any of the muscles may be noted during this examination. Testing the eyes separately can be helpful when there is misalignment present. Vergences are the result of the eyes moving in opposite directions such as convergence and divergence and are testing by having the patient look at an object moving toward them and away from them.
The accommodative-convergence complex — A review
Published in Jan-Tjeerd de Faber, 28th European Strabismological Association Meeting, 2020
R.L. Brautaset, J.A.M. Jennings
The controllers for both the accommodation and vergence loops have fast and slow components. The fast component reacts quickly but fatigues when having to maintain innervation. The output of the fast component is the input to the slow component. The slow system reacts more slowly but does not fatigue easily. The longer time constant (the time for the exponential response to reach 63% of its final output) of the decay of the slow component causes the slow component to continue its innervation even after the stimulus has been removed. This may be observed by noting the esophoric shift in the phoria after measuring vergence with base-out prisms (Saladin, 1986). The slow component is responsible for allowing the system to adjust to changes overtime (i.e. adaptation).
Visual function impairment in patients suffering from visually induced motion sickness. A preliminary observational longitudinal study
Published in Hearing, Balance and Communication, 2023
Leonardo Gabriele, Sara De Angelis, Vittorio Roncagli, Marco Tramontano, Leonardo Manzari, Domenico Gabriele
Two evaluation sessions were carried out immediately before (T0) and after 16 weeks of visual rehabilitation training (T1) (Figure 1). Each evaluation aimed to evaluate participants’ visual function and sickness-related symptoms. Visual function evaluation consisted of vergence and accommodative tests, binocular vision, stereopsis and phoria. The function of the vergence eye movement system is to track objects moving in depth, to attain cortical fusion and bifoveation. Visual accommodation is a reflexive physical process in which the lens of the eye adjusts allowing images to become focussed. The stereopsis is the perception of depth produced by the reception in the brain of visual stimuli from both eyes in binocular vision. The phoria is characterized by a latent horizontal and vertical deviation of the visual axes.
Adherence to home-based videogame treatment for amblyopia in children and adults
Published in Clinical and Experimental Optometry, 2021
Tina Y Gao, Joanna M Black, Raiju J Babu, William R Bobier, Arijit Chakraborty, Shuan Dai, Cindy X Guo, Robert F Hess, Michelle Jenkins, Yannan Jiang, Lisa S Kearns, Lionel Kowal, Carly S Y Lam, Peter C K Pang, Varsha Parag, Roberto Pieri, Rajkumar Nallour Raveendren, Jayshree South, Sandra Elfride Staffieri, Angela Wadham, Natalie Walker, Benjamin Thompson
It may be that for treatments based on visual stimulation to be successful, detailed instructions need to be given to patients (and parents/caregivers where relevant) specifying the optimal session length and emphasising the need to continuously view the display for maximum effect. However, continuous viewing must be enforced in a friendly manner to be acceptable to the user, and longer training sessions need to be balanced against the fact that they are less convenient to schedule within the patient’s daily routine. Inconvenient or unpleasant treatments will hinder overall treatment adherence, which can also lead to reduced effectiveness. This balance between training intensity and practicality is an important design consideration for all home-based treatments, and the optimal balance will depend on many factors including patient age, ability, lifestyle factors (e.g. school, work, and/or family responsibilities), the treatment delivery method (e.g. portable versus not portable), and, importantly, the true impact of disrupted play on treatment outcomes, which may vary depending on the condition being treated and the mechanisms underlying the treatment effects. Traditional vision therapy exercises for vergence disorders, for example, are often prescribed with a ‘little but often’ daily regimen to minimise ocular fatigue. But this may not be suitable for all training-type therapies.
Association between post-concussion symptoms and oculomotor deficits among adolescents
Published in Brain Injury, 2021
Sowjanya Gowrisankaran, Ankoor S. Shah, Tawna L. Roberts, Emily Wiecek, Ryan N. Chinn, Karameh K Hawash, Michael J. O’Brien, David R Howell, William P Meehan, Aparna Raghuram
Oculomotor assessment included evaluation of vergence, accommodation, and visual tracking. The following tests were performed to evaluate vergence: eye alignment at distance and near (unilateral and alternating prism cover test); near point of convergence (NPC); vergence amplitudes, including convergence (Positive Fusional Vergence) and divergence (Negative Fusional Vergence) at near (40 cm); and near vergence facility using a prism wedge of 3Δ base in (BI) and 12Δ base out (BO). The following tests were used to evaluate the accommodation system: amplitude of accommodation using the push-up method and monocular and binocular accommodative facility using ± 2.00 D flippers. The developmental eye movement (DEM) test was used to evaluate visual tracking ability. A detailed description of the tests can be found in earlier publications (27,34). Results of oculomotor testing were used to provide vergence, accommodation, and visual tracking deficit diagnoses to each patient, based on criteria described in (Table 1) (17,27).