Difference between revisions of Axial length

(12 intermediate revisions by 5 users not shown)

Line 1:

'''Axial length''' of the eyeball is the scientifically accurate reason why ~~anyone has~~ [[myopia]].

'''Axial length''' of the eyeball is the distance from the lens to the retina. Axial elongation is the scientifically accurate reason why most myopes have [[myopia]], as other causes are rare.

==Biology==

It would require precision engineering to be able to grow an eye that was perfectly [[emmetropic]] at birth. Instead, it is of approximate dimensions, and feedback during postnatal development tunes the axial length to match the focusing system. Two mechanisms are available: changing the thickness of the [[choroid]], and changing the length of the eyeball itself. <ref>{{cite journal| author=Wallman J, Winawer J| title=Homeostasis of eye growth and the question of myopia. | journal=Neuron | year= 2004 | volume= 43 | issue= 4 | pages= 447-68 | pmid=15312645 | doi=10.1016/j.neuron.2004.08.008 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15312645}}</ref>

==How it can be reduced==

[[Myopic defocus]], as well as conscious accommodation of the ciliary muscle during [[active focus]]. ~~Finally,~~ good [[distance vision]] practices.

[[Myopic defocus]], as well as conscious accommodation of the ciliary muscle during [[active focus]], can cause axial shortening. Having good [[close-up]] and [[distance vision]] practices helps.

==How it can be increased==

:''Main article: [[Axial elongation]]''

[[Hyperopic defocus]], excessive [[myopic defocus]], form deprivation, and [[accommodation]] strain can all cause [[axial elongation]]. In particular, using distances glasses for close-up is a very common cause of it.

==Controversy==

Hyperopes tend not to report back with any progress toward 20/20 vision. An implication is that EndMyopia techniques may not work for far-sighted people. This may indicate that we aren't changing axial length with EndMyopia techniques. Another theory is that EndMyopia might work by flattening the lens. It's easier to flatten a lens than to squeeze it, so this would explain why EndMyopia doesn't seem to attract people with hyperopic vision. Probably related, see also [[Dr. Carr]].

==Further Reading==

* https://pubmed.ncbi.nlm.nih.gov/19204786/

* http://www.molvis.org/molvis/v15/a31/mv-v15-a31-yang.pdf

* https://endmyopia.org/wp-content/uploads/2017/02/Reduction_in_Axial_Length_with_Age__An.3.pdf

* https://iovs.arvojournals.org/article.aspx?articleid=2126435

==References==

[[Category:Articles]]

@@ Line 1: / Line 1: @@
-'''Axial length''' of the eyeball is the scientifically accurate reason why anyone has [[myopia]].
+'''Axial length''' of the eyeball is the distance from the lens to the retina. Axial elongation is the scientifically accurate reason why most myopes have [[myopia]], as other causes are rare.
 ==Biology==
+It would require precision engineering to be able to grow an eye that was perfectly [[emmetropic]] at birth. Instead, it is of approximate dimensions, and feedback during postnatal development tunes the axial length to match the focusing system. Two mechanisms are available: changing the thickness of the [[choroid]], and changing the length of the eyeball itself. <ref>{{cite journal| author=Wallman J, Winawer J| title=Homeostasis of eye growth and the question of myopia. | journal=Neuron | year= 2004 | volume= 43 | issue= 4 | pages= 447-68 | pmid=15312645 | doi=10.1016/j.neuron.2004.08.008 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15312645}}</ref>
 ==How it can be reduced==
-[[Myopic defocus]], as well as conscious accommodation of the ciliary muscle during [[active focus]]. Finally, good [[distance vision]] practices.
+[[Myopic defocus]], as well as conscious accommodation of the ciliary muscle during [[active focus]], can cause axial shortening. Having good [[close-up]] and [[distance vision]] practices helps.
+==How it can be increased==
+:''Main article: [[Axial elongation]]''
+[[Hyperopic defocus]], excessive [[myopic defocus]], form deprivation, and [[accommodation]] strain can all cause [[axial elongation]]. In particular, using distances glasses for close-up is a very common cause of it.
+==Controversy==
+Hyperopes tend not to report back with any progress toward 20/20 vision.  An implication is that EndMyopia techniques may not work for far-sighted people.  This may indicate that we aren't changing axial length with EndMyopia techniques.  Another theory is that EndMyopia might work by flattening the lens.  It's easier to flatten a lens than to squeeze it, so this would explain why EndMyopia doesn't seem to attract people with hyperopic vision.  Probably related, see also [[Dr. Carr]].
+==Further Reading==
+* https://pubmed.ncbi.nlm.nih.gov/19204786/
+* http://www.molvis.org/molvis/v15/a31/mv-v15-a31-yang.pdf
+* https://endmyopia.org/wp-content/uploads/2017/02/Reduction_in_Axial_Length_with_Age__An.3.pdf
+* https://iovs.arvojournals.org/article.aspx?articleid=2126435
+==References==
+{{reflist}}
+[[Category:Articles]]