Also known as pressure phosphene. The two terms are used interchangeably to denote a type of "phosphene (i.e. 'seeing stars') that can be provoked under physiological conditions by the exertion of gentle pressure on the eyeball. Deformation phosphenes are classified as "entoptic phenomena. They may present as a darkening of the visual field, as diffuse colour patches, as changing, scintillating, and deforming light-grids with occasional dark spots, or as a field that is sparsely covered with intense blue points of light. The earliest known description of the deformation phosphene was recorded by the Greek philosopher and medical theorist Alcmaeon of Croton, who lived in the mid-fifth century BC. Under the influence of "hallucinogens such as mescaline and LSD, the induction ofdeformation phosphenes can trigger a kaleidoscopic series of " visual hallucinations.
References
Grüsser, O.-J., Hagner, M. (1990). On the history of deformation phosphenes and the idea of internal light generated in the eye for the purpose of vision. Documenta Ophthalmologica, 74, 57-85.
Dictionary of Hallucinations. J.D. Blom. 2010.