appears as one or more light disks crossed by dark blurry lines (the shadows of the lashes), each having fringes of spectral colour. The disk shape is given by the circular aperture of the pupil. See also Theory of Colours References Sources 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; 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/. 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. External links Picture of the entoptic phenomenon: Vitreous Floaters (PDF file, requires an Acrobat Reader or plugin) Diagram of entoptic subjective visual phenomena Video describing history and science of first entoptic viewing technique Video describing history and science of second entoptic viewing technique The Relation Between Migraine, Typical Migraine Aura and “Visual Snow” Ophthalmology Vision