內視現象

內視現象（Entoptic phenomenon）是一種由人眼本身的內部造成的視覺效果。（有時也稱為entopic phenomenon ，可能是印刷錯誤。）
用亥姆霍茲話來說：「在合適的條件下，落在眼睛上的光線可能致使我們得以看見眼睛內的某些物體。這些知覺稱為「內視」（entoptical）。」

**概述**
內視影像所投射在視網膜上的影像有其物理基礎，這與由視覺系統引起的視錯覺不同，視錯覺的特點是視知覺似乎與現實不同。內視影像則是由觀察者自己眼睛內部的現象引起的，這種影像與視錯覺和幻覺有個共同之處，觀察者都無法與其他人分享對於這種現象的直接和特定的觀點。
亥姆霍茲helmholtz說明瞭某些觀察者可輕易看見而其他人卻完全看不到的內視現象。這種差異不足為奇，因為產生這些影像的眼睛，在具體的層面上對每個人來說都是獨一無二的。由於個體之間有所差異，加上兩個觀察者無法共享一個幾乎相同的刺激，所以這些現象與大多數視覺感覺不同，也不同於大多數藉由觀察共同刺激所產生的視錯覺。不過主要的內視現象之間有充足的共性，現在已能令人滿意地解釋其物理成因。

**例子**
內視效應的一些例子包括：

**參見**
 關於鬼的科學解釋- 耳內現象（Endaural phenomena）- 結構衡量（Form Constant）- 臨睡幻覺（hypnagogia）- 感覺剝奪箱（Isolation tank）- 囚人戲劇（prisoner's cinema）- 閃爍的視野缺損（scintillating scotoma）- 視雪症- 藍天內視現象- 飛蚊症- 《論色彩學》（Theory of Colours）

**參考文獻**
 Jan E. Purkyně, 1823: Beiträge zur Kenntniss des Sehens in subjectiver Hinsicht in Beobachtungen und Versuche zur Physiologie der Sinne, In Commission der J.G. Calve'schen Buchhandlung, Prag.- H. von Helmholtz, Handbuch der Physiologischen Optik, published as "Helmholtz's Treatise on Physiological Optics, Translated from the Third German Edition," ed. James P. C. Southall; 1925; The Optical Society of America.- Leonard Zusne, 1990: Anomalistic Psychology: A Study of Magical Thinking; Lea; 0-8058-0508-7  date=20071114212320 - Becker, O., 1860, “Über Wahrnehmung eines Reflexbildes im eigenen Auge About perception of a reflected image in your own eye,” Wiener Medizinische Wochenschrift, pp. 670 672 & 684 688.- M. Tscherning, 1920, Physiologic Optics; Third Edition, (English translation by C. Weiland). Philadelphia: Keystone Publishing Co. pp. 55–56.- White, Harvey E., and Levatin, Paul, 1962, "'Floaters' in the eye," Scientific American, Vol. 206, No. 6, June, 1962, pp. 199 127.- Duke Elder, W. S. (ed.), 1962, System of Ophthalmology, Volume 7, The Foundations of Ophthalmology: heredity pathology diagnosis and therapeutics, St. Louis, The C.V. Mosby Company. p450.- Snodderly, D.M., Weinhaus, R.S., & Choi, J.C. (1992). Neural-vascular relationships in central retina of Macaque monkeys (Macaca fascicularis). Journal of Neuroscience, 12(4), 1169-1193. Available online at: http://www.jneurosci.org/cgi/reprint/12/4/1169.pdf.- Sinclair, S.H., Azar-Cavanagh, M., Soper, K.A., Tuma, R.F., & Mayrovitz, H.N. (1989). Investigation of the source of the blue field entoptic phenomenon. Investigative Ophthalmology & Visual Science, 30(4), 668-673. Available online at: http://www.iovs.org/ date=20150322000208 .- Giles Skey Brindley, Physiology of the Retina and Visual Pathway, 2nd ed. (Edward Arnold Ltd., London, 1970), pp. 140–141.- Bill Reid, “Haidinger's brush,” Physics Teacher, Vol. 28, p. 598 (Dec. 1990).- Walker, J., 1984, “How to stop a spinning object by humming and perceive curious blue arcs around the light,” Scientific American, February, Vol. 250, No. 2, pp. 136 138, 140, 141, 143, 144, 148.

**外部連結**
 Entoptic+Vision-  Picture of the entoptic phenomenon: Vitreous Floaters date=20190612194449  (PDF file, requires an Acrobat Reader or plugin)-  Diagram of entoptic subjective visual phenomena date=20190613035528 -  Video describing history and science of first entoptic viewing technique date=20200226084909 -  Video describing history and science of second entoptic viewing technique date=20200410084537 -  The Relation Between Migraine, Typical Migraine Aura and “Visual Snow” date=20171225033640