Difference between revisions of Eye strain
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'''Eye strain''', or '''asthenopia''', is fatigue of the ciliary muscles and extraocular muscles. Eye strain does not cause [[myopia]], but it can lead to [[pseudomyopia]]. Eye strain can lead to discomfort, including soreness and redness. As a rule the goal of [[ | '''Eye strain''', or '''asthenopia''', is fatigue of the ciliary muscles and extraocular muscles. Eye strain does not cause [[myopia]], but it can lead to [[pseudomyopia]]. Eye strain can lead to discomfort, including soreness and redness. As a rule the goal of the [[reduced lens method]] is to use stimulus without causing unnecessary strain. | ||
==The over-worked muscles== | ==The over-worked muscles== | ||
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==Distance Vision Strain== | ==Distance Vision Strain== | ||
Some participants report feeling strain after long sessions of distance active focus. | Some participants report feeling strain after long sessions of distance active focus. | ||
One suggestion for handling distance strain is to balance both near and far accommodation, which is referred sometimes as "dynamic vision" activity. [https://www.youtube.com/watch?v=GM59lsIsl4M] | |||
Different theories which are still in contention were proposed to describe the mechanism of accommodation. Some of those theories are: | Different theories which are still in contention were proposed to describe the mechanism of accommodation. Some of those theories are: | ||
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'''Schacher theory of accommodation (2006)'''- This theory states that when the lens is in focus, there is increased tension on the lens through the equatorial zonular fibers and when there is contraction of the ciliary muscle, the zonular fibers located equatorially increase their tensile strength. This results in the steepness of the central surface of the lens, an increase in thickness of the lens and a flattening of the lens edges. As the tension on the equatorial zonular fibers increase during accommodation, the anterior and posterior zonular fibers relax. The anterior and posterior zonular fibers serve as passive support structures for the lens, but the equatorial zonular fibers determines the refractive power of the lens. | '''Schacher theory of accommodation (2006)'''- This theory states that when the lens is in focus, there is increased tension on the lens through the equatorial zonular fibers and when there is contraction of the ciliary muscle, the zonular fibers located equatorially increase their tensile strength. This results in the steepness of the central surface of the lens, an increase in thickness of the lens and a flattening of the lens edges. As the tension on the equatorial zonular fibers increase during accommodation, the anterior and posterior zonular fibers relax. The anterior and posterior zonular fibers serve as passive support structures for the lens, but the equatorial zonular fibers determines the refractive power of the lens. | ||
Possibly related to: Theory of Reciprocal Zonular Action: | |||
https://www.youtube.com/watch?v=1yIpyitm6eE | |||
'''Catenary theory of accommodation (1970)'''– This theory is also called the Coleman theory of accommodation. It states that the lens and the zonula fibers form a diaphragm, which is held in a catenary (a curve formed by a wire, rope, or chain hanging freely from two points that are not in the same vertical line) shape due to the difference in pressure between the aqueous and vitreous bodies of the lens. A change in diameter of the ciliary body results in a change of the catenary shape. It means there is a continuous pressure difference on the lens. The strength of this pressure difference is approximately 2.3 cm of water column, with major changes occurring during the initial seconds of the accommodation phase. The anterior capsule and the zonular fibers form hammock shaped surface that is duplicable but depends on the diameter of the ciliary body. The ciliary body however makes a shape like the pillars of a suspension bridge, but does not need to support the force around the equator to flatten the lens. | '''Catenary theory of accommodation (1970)'''– This theory is also called the Coleman theory of accommodation. It states that the lens and the zonula fibers form a diaphragm, which is held in a catenary (a curve formed by a wire, rope, or chain hanging freely from two points that are not in the same vertical line) shape due to the difference in pressure between the aqueous and vitreous bodies of the lens. A change in diameter of the ciliary body results in a change of the catenary shape. It means there is a continuous pressure difference on the lens. The strength of this pressure difference is approximately 2.3 cm of water column, with major changes occurring during the initial seconds of the accommodation phase. The anterior capsule and the zonular fibers form hammock shaped surface that is duplicable but depends on the diameter of the ciliary body. The ciliary body however makes a shape like the pillars of a suspension bridge, but does not need to support the force around the equator to flatten the lens. | ||
[https://community.endmyopia.org/t/distance-vision-strain/17674 forum discussion on distance strain] | [https://community.endmyopia.org/t/distance-vision-strain/17674 forum discussion on distance strain] | ||
==References== | ==References== | ||