entoptic

Entoptic describes visual phenomena that originate within the eye itself rather than from external objects. The term comes from Greek roots entos “inside” and optos “seen” and is used in ophthalmology and vision science to distinguish internal from external sources of vision. Most entoptic phenomena are normal and temporary, produced by the anatomy or physiology of the eye, such as the cornea, lens, vitreous humor, retina, or intraocular blood vessels, or by the neural processing of visual information.

Common examples include floaters (myodesopsia), caused by tiny opacities or inhomogeneities in the vitreous humor that cast shadows on the retina, often seen as specks or threads that drift with eye movement; the blue field entoptic phenomenon, where small moving white cells in retinal capillaries appear against a bright blue field; Haidinger’s brush, a subtle yellowish pattern seen under polarized light, reflecting the eye’s polarization sensitivity; and the Purkinje tree, a faint, branching pattern produced by shadows of retinal vessels when looking at a bright light. Phosphenes—percepts of light without external light input, produced by stimulation of the retina or visual pathways—are sometimes described as entoptic because their origin is internal.

While most entoptic phenomena are harmless, a sudden or persistent change in visual phenomena such as new floaters, flashes, or a marked increase in spots should be evaluated for possible retinal pathology.