Changes

== Physiology ==

== Physiology ==

A vergence-focal conflict is caused due to factors in human physiology like the [[accommodation reflex]]. Focal conflict occurs when the human brain receives mismatching cues between [[vergence]] and [[Accommodation (eye)|accommodation]].<ref name="kramida">{{Cite web |date=2022-09-22 |title=Resolving the Vergence-Accommodation Conflict in Head-Mounted Displays |url=https://3dvar.com/Kramida2016Resolving.pdf |access-date=2022-09-22 |archive-url=https://web.archive.org/web/20220922032435/https://3dvar.com/Kramida2016Resolving.pdf |archive-date=2022-09-22 |url-status=live}}</ref><ref>{{Cite journal |last1=Zhou |first1=Yao |last2=Zhang |first2=Jufan |last3=Fang |first3=Fengzhou |date=2021-12-01 |title=Vergence-accommodation conflict in optical see-through display: review and prospect |journal=Results in Optics |language=en |volume=5 |pages=100160 |doi=10.1016/j.rio.2021.100160 |s2cid=241361232 |issn=2666-9501|doi-access=free }}</ref><ref>{{Cite journal |last=Konrad |first=Robert |date=2015-11-06 |title=What is the vergence-accommodation conflict and how do we fix it? |url=https://doi.org/10.1145/2810048 |journal=XRDS: Crossroads, the ACM Magazine for Students |volume=22 |issue=1 |pages=52–55 |doi=10.1145/2810048 |s2cid=9330080 |issn=1528-4972}}</ref><ref name=anses>{{Cite web |date=2014-11-06 |title=3D technologies and eyesight: use not recommended for children under the age of six, use in moderation for those under the age of 13 |url=https://www.anses.fr/en/content/3d-technologies-and-eyesight-use-not-recommended-children-under-age-six-use-moderation-0 |access-date=2022-09-22 |website=Anses |language=en}}</ref> It often causes headaches and visual fatigue.<ref>{{Cite journal |last1=Hoffman |first1=David M. |last2=Girshick |first2=Ahna R. |last3=Akeley |first3=Kurt |last4=Banks |first4=Martin S. |date=2008-03-01 |title=Vergence–accommodation conflicts hinder visual performance and cause visual fatigue |url=https://jov.arvojournals.org/article.aspx?articleid=2122611 |journal=Journal of Vision |language=en |volume=8 |issue=3 |pages=33.1–30 |doi=10.1167/8.3.33 |issn=1534-7362 |pmc=2879326 |pmid=18484839}}</ref> The vergence-accommodation conflict is one of the main causes of [[virtual reality sickness]].<ref>{{Cite journal |last1=Lawson |first1=Ben D. |last2=Stanney |first2=Kay M. |date=2021 |title=Editorial: Cybersickness in Virtual Reality and Augmented Reality |journal=Frontiers in Virtual Reality |volume=2 |doi=10.3389/frvir.2021.759682 |issn=2673-4192|doi-access=free }}</ref>

A vergence-focal conflict is caused due to factors in human physiology like the [[accommodation reflex]]. Focal conflict occurs when the human brain receives mismatching cues between [[vergence]] and [[Accommodation (eye)|accommodation]].<ref name="kramida">{{Cite web |date=2022-09-22 |title=Resolving the Vergence-Accommodation Conflict in Head-Mounted Displays |url=https://3dvar.com/Kramida2016Resolving.pdf |access-date=2022-09-22 |archive-url=https://web.archive.org/web/20220922032435/https://3dvar.com/Kramida2016Resolving.pdf |archive-date=2022-09-22 |url-status=live}}</ref><ref>{{Cite journal |last=Konrad |first=Robert |date=2015-11-06 |title=What is the vergence-accommodation conflict and how do we fix it? |url=https://doi.org/10.1145/2810048 |journal=XRDS: Crossroads, the ACM Magazine for Students |volume=22 |issue=1 |pages=52–55 |doi=10.1145/2810048 |s2cid=9330080 |issn=1528-4972}}</ref><ref name=anses>{{Cite web |date=2014-11-06 |title=3D technologies and eyesight: use not recommended for children under the age of six, use in moderation for those under the age of 13 |url=https://www.anses.fr/en/content/3d-technologies-and-eyesight-use-not-recommended-children-under-age-six-use-moderation-0 |access-date=2022-09-22 |website=Anses |language=en}}</ref> It often causes headaches and visual fatigue.<ref>{{Cite journal |last1=Hoffman |first1=David M. |last2=Girshick |first2=Ahna R. |last3=Akeley |first3=Kurt |last4=Banks |first4=Martin S. |date=2008-03-01 |title=Vergence–accommodation conflicts hinder visual performance and cause visual fatigue |url=https://jov.arvojournals.org/article.aspx?articleid=2122611 |journal=Journal of Vision |language=en |volume=8 |issue=3 |pages=33.1–30 |doi=10.1167/8.3.33 |issn=1534-7362 |pmc=2879326 |pmid=18484839}}</ref> The vergence-accommodation conflict is one of the main causes of [[virtual reality sickness]].<ref>{{Cite journal |last1=Lawson |first1=Ben D. |last2=Stanney |first2=Kay M. |date=2021 |title=Editorial: Cybersickness in Virtual Reality and Augmented Reality |journal=Frontiers in Virtual Reality |volume=2 |doi=10.3389/frvir.2021.759682 |issn=2673-4192|doi-access=free }}</ref>

Two ocular responses exist: vergence of eyes, and focus, also known as accommodation. Both of these mechanisms are crucial in stereoscopic vision. Vergence or independent inward/outward rotation of eyes is engaged to fixate on objects and perceive them as single. Incorrect vergence response can cause double vision. Accommodation is the eye’s focusing mechanism and it is engaged to produce a sharp image on a retina. Both of these mechanisms are neurally linked forming the accommodation-convergence reflex<ref>{{Cite web |title=Reflex action {{!}} Definition, Types and Mechanism and Important solved questions |date=11 November 2020 |url=https://www.crackyourtarget.com/reflex-action.html}}</ref> of eyes. One can distinguish vergence {{nowrap|distance{{px2}}{{mdash}}{{px2}}}}a distance of a point towards which both eyes are converging, and an accommodation {{nowrap|distance{{px2}}{{mdash}}{{px2}}}}a distance of a region in space towards which the focus or refractive power of the crystalline lens has been adjusted to produce a sharp image on the retina.

Two ocular responses exist: vergence of eyes, and focus, also known as accommodation. Both of these mechanisms are crucial in stereoscopic vision. Vergence or independent inward/outward rotation of eyes is engaged to fixate on objects and perceive them as single. Incorrect vergence response can cause double vision. Accommodation is the eye’s focusing mechanism and it is engaged to produce a sharp image on a retina. Both of these mechanisms are neurally linked forming the accommodation-convergence reflex<ref>{{Cite web |title=Reflex action {{!}} Definition, Types and Mechanism and Important solved questions |date=11 November 2020 |url=https://www.crackyourtarget.com/reflex-action.html}}</ref> of eyes. One can distinguish vergence {{nowrap|distance{{px2}}{{mdash}}{{px2}}}}a distance of a point towards which both eyes are converging, and an accommodation {{nowrap|distance{{px2}}{{mdash}}{{px2}}}}a distance of a region in space towards which the focus or refractive power of the crystalline lens has been adjusted to produce a sharp image on the retina.