CONVERGENCE PHOSPHENE

   A term used to denote a *phosphene (i.e. 'seeing stars') arising physiologically in association with convergence of the eyes. In 1978 the American neuroscientist Christopher W. Tyler proposed a distinction between two types of convergence phosphene: one mediated by rapid convergence movements, and one mediated by prolonged convergence movements. Phenomenologi-cally, the type of phosphene which follows rapid convergence movements is characterized by two large rings that can be seen best in a dark environment. This type is also referred to as the fiery rings of Purkinje, after the Bohemian physiologist Johannes Evangelista Purkyne (1787-1869), who described the phenomenon in his textbook of 1823.The mediation of the fiery rings of Purkinje is attributed to stretching of the optic nerves and the region of the papillae, followed by peripheral neuronal discharges. The second type of convergence phosphene, occurring after sustained convergence of the eyes, can be best perceived with eyes closed against an illuminated background. This type is characterized by a red dumbbell-shaped form that extends horizontally from the region of the fovea to the periphery. Because of its shape, this type of phosphene is also referred to as a dumbbell phosphene or dumbbell-shaped phosphene. Convergence phosphenes are classified either as *entoptic phenomena or as * physiological illusions. The term convergence phosphene is used in opposition to the terms *flick phosphene, *movement phosphene, and *sound phosphene.

   References

   Purkyne, J.E. (1823). Beobachtungen und Versuche zur Physiologie der Sinne I. Prague: Calve.

   Tyler, C.W. (1978). Some new entoptic phenomena. Vision Research, 18, 1633-1639.