Entoptic Phenomena

Entoptic phenomena are perceptions generated by the eye’s own anatomy and physiology. This chapter reviews halos around lights resulting from the natural lens fibers which can act as a diffraction grating, corneal edema from various pathologic states, and both negative and positive dysphotopsias. Floaters can result from vitreous syneresis and are known as muscae volitantes . The chapter contains reviews of Scheerer’s phenomenon and Shafer’s sign (tobacco dust). Phosphenes, or flashes of light that occur without an actual light source, may be generated by retinal stimulation through prolonged accommodation, quick eye movement or digitally pressing an eye. Moore’s lightning streaks and other induced visual disturbances, such as Purkinje tree and light emitting diode headlights, are also introduced.