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Vision System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Aaron P. Batista and George D. Stetten
When the images arriving at the two retinas cannot be combined, one or the other image is rejected. is phenomenon is known as binocular rivalry, and if a chronic condition, it can lead to blindness in one eye. e general term amblyopia refers to the partial or complete loss of eyesight not caused by abnormalities in the eye. e most common form of amblyopia is caused by strabismus, in which the eyes are not aimed in a parallel direction, but rather are turned inward (cross-eyed) or outward (walleyed). is condition leads to habitual suppression of vision from one of the eyes and sometimes to blindness in that eye or to alternation, in which the subject maintains vision in both eyes by using only one eye at a time. Cutting selected ocular muscles in kittens causes strabismus, and the kittens respond by developing alternation, preserving functional vision in both eyes. However, the number of cells in the cortex displaying binocular responses becomes greatly reduced. In humans with long-standing alternating strabismus, surgical repair to make the eyes parallel again does not bring back a sense of depth. Permanent damage has been caused by the subtle condition of the images on the two retinas not coinciding. is may be explained by the Hebbian model for associative learning, in which temporal association between inputs strengthens synaptic connections (Hebb, 1961).
Impact of Retinal Stimulation on Neuromodulation
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
What should be noted is not all studies have found improvements from neuro-optometric treatments. However, tests that have failed often have not considered particular variables. For instance, one study included more than 5500 children with reading impairments. They were evaluated for eye problems involving image-forming (eyesight) circuitry. Conclusion was that no optometric vision rehabilitation would be helpful. Strabismus, motor fusion, sensory fusion at a distance, refractive error, amblyopia, convergence, accommodation, or contrast sensitivity were not significantly different in those children when they were compared to children with normal reading ability (Creavin et al. 2015). However, this study did not take into account all the linkages between the eyes and other sensory systems. For instance, dyslexia involves auditory/visual interactions.
From Vision Science to Design Practice
Published in Marcelo M. Soares, Francisco Rebelo, Ergonomics in Design Methods & Techniques, 2016
Cristina Pinheiro, Fernando Moreira da Silva
Amblyopia, also known as low vision means a reduced visual capacity—whatever the origin— that does not improve using optical correction. There is a low visual acuity either of organic origin (organic amblyopia—with injuries to the eyeball or the optic tracts), whether functional (functional amblyopia—without organic damage).
The changing scope of Optometry in New Zealand: historical perspectives, current practice and research advances
Published in Journal of the Royal Society of New Zealand, 2019
Joanna M. Black, Robert J. Jacobs, John R. Phillips, Monica L. Acosta
Paediatric vision studies are an important research theme within SOVS with early studies investigating visual acuity measurement in children (Carkeet et al. 1997) (Garner et al. 1997). Research on paediatric populations has also included the development of new treatments for amblyopia. Amblyopia or ‘lazy eye’ is a neurodevelopmental disorder of vision which effects approximately 3% of children. Traditionally, patching therapy is prescribed, to strengthen the weaker eye by blocking vision to the normally developing eye. A number of studies have been conducted investigating the binocular basis of amblyopia and inter-ocular suppression. These suggest that binocular treatments may give more sustained visual improvements. The binocular treatment of amblyopia using videogames (BRAVO) study was a randomized placebo-controlled double-masked clinical trial led by Auckland that involved multiple international sites. The aim was to assess the effectiveness of a binocular videogame treatment when used at home for children ≥7 years of age and adults. The study result was that both the active and placebo game improved visual acuity following the trial (Gao, Guo, et al. 2018), and that refractive correction shows significant improvements in visual acuity in adults and children (Gao, Anstice, et al. 2018). A Phase II clinical trial of a related binocular therapy – developed by researchers at Auckland – is commencing at Moorfields Eye Hospital in the UK at the time of writing.