This is because their eyes are struggling to maintain fusion. Intermittent strabismics tend to have more symptoms of double vision, eye fatigue, and words moving on a page while reading. Patients with constant strabismus do not have stereopsis, or proper development of binocularity, and often develop sensory adaptations to maintain single vision. A constant unilateral strabismus may or may not have associated amblyopia. Strabismus can be constant or intermittent. The prevalence of strabismus is estimated at 2-5% of the population, similar to the prevalence of amblyopia. Strabismus is an inward eye turn (esotropia) or outward eye turn (exotropia). With adults, it can difficult to judge how much improvement can be made, but the adult brain has significant neuroplasticity and improvement to the visual system is possible. Patients who have dizziness and balance disorders and also have longstanding amblyopia may benefit from attempting to improve vision in their amblyopic eye and improving their binocularity if treatment has not been attempted in the past. Optometric vision therapy may improve visual acuity in the amblyopic eye, and improve binocularity. This means that suppression need not be permanent. If the inhibition is removed, the visual cortex is able respond to signals from both eyes.
Researchers have discovered that suppression is caused by the development of a GABA neurotransmitter inhibitory network in the visual cortex (e.g. Suppression can be defined as an inhibitory force the dominant eye exerts on the amblyopic eye, which reduces the amblyopic eye’s contribution to the brain’s image. A binocular treatment approach focuses on reducing interocular suppression.
Recent research has shown that a binocular approach to treating amblyopia may be more effective, and a better treatment option for adults. Historically, amblyopia has been treated with patching therapy in children. Patients with amblyopia also have inaccurate accommodation (focusing), reduced contrast sensitivity, unsteady fixation, reduced oculomotor skills, spatial uncertainty, interocular suppression (see below), and reduced binocularity. Amblyopia is typically caused by a constant strabismus (eye turn), anisometropia (high refractive error in one eye), or form deprivation (typically a congenital cataract) which develops before the age of 6 years. It is a developmental disorder of the brain visual cortex, the hallmark of which is reduced visual acuity in one eye, arising from abnormal visual experience early in life (Levi et al, 2015) . AmblyopiaĪmblyopia is the most common visual impairment affecting one eye, with a prevalance of about 1-5% of the world population (Bonaccorsi et al, 2014).
It is also possible to have a torsional misalignment between the two eyes. There are several types of binocular vision disorders, including amblyopia, constant or intermittent strabismus, disorders of maintaining horizontal eye alignment ( convergence insufficiency, convergence excess, divergence insufficiency, divergence excess) and vertical heterophoria. This suggests treating binocular vision disorders may improve quality of life in patients with vestibular dysfunction. The presence of binocular vision disorders may limit the effectiveness of vestibular therapy (Pavlau et al, 2015). When the binocular visual system and vestibular system are not properly integrated, dizziness and sensitivity to visual motion may result. Symptoms of binocular vision dysfunction include eyestrain, double vision, blurred vision, visual fatigue, and headaches. The visual system must converge (turn eyes inward) and diverge (turn eyes outward) to maintain a clear, single, three-dimensional image. Depth perception helps orient the body in space. Binocular vision refers to how the eyes work together to produce a three-dimensional perception of the world.
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