This makes the dots of light appear slightly elongated with dark tails. As a large, deformed white blood cell goes through a capillary, a space opens up in front of it and red blood cells pile up behind. White cells are larger than red blood cells and can be larger than the diameter of a capillary, so must deform to fit. ![]() It is much more noticeable when viewed against a field of pure blue light and is caused by white blood cells moving in the capillaries in front of the retina. Blue field entoptic phenomenon has the appearance of tiny bright dots moving rapidly along squiggly lines in the visual field.The first two sort of floaters may collect over the fovea (the center of vision), and therefore be more visible, when a person is lying on his or her back looking upwards. Others may be "coagula of the proteins of the vitreous gel, to embryonic remnants, or the condensation round the walls of Cloquet's canal" that exist in pockets of liquid within the vitreous. Others may be chains of red blood cells stuck together diffraction patterns can be seen around these. Some may be individual red blood cells swollen due to osmotic pressure. They are visible because they move if they were pinned to retina by the vitreous or fixed within the vitreous they would be as invisible as ordinary viewing of any stationary object, such as the retinal blood vessels (see Purkinje tree below). They are shadow images of objects floating in liquid between the retina and the jelly inside the eye (the vitreous) or in the vitreous humor itself. Floaters or muscae volitantes are slowly drifting blobs of varying size, shape, and transparency, which are particularly noticeable when viewing a bright, featureless background (such as the sky) or a point source of diffuse light very close to the eye.Some examples of entoptical effects include:įloaters depiction Purkinje tree depiction Yet, there is enough commonality between the main entoptic phenomena that their physical origin is now well understood. They are also unlike most optical illusions which are produced by viewing a common stimulus. Because of the variation between individuals, and the inability for two observers to share a nearly identical stimulus, these phenomena are unlike most visual sensations. This variance is not surprising because the specific aspects of the eye that produce these images are unique to each individual. Helmholtz commented on entoptic phenomena which could be seen easily by some observers, but could not be seen at all by others. Because entoptic images are caused by phenomena within the observer's own eye, they share one feature with optical illusions and hallucinations: the observer cannot share a direct and specific view of the phenomenon with others. Hence, they are different from optical illusions, which are caused by the visual system and characterized by a visual percept that (loosely said) appears to differ from reality. These perceptions are called entoptical."Įntoptic images have a physical basis in the image cast upon the retina. In Helmholtz's words: "Under suitable conditions light falling on the eye may render visible certain objects within the eye itself. (Occasionally, these are called entopic phenomena, which is probably a typographical mistake.) The numerous visual presentations need to be differentiated so that appropriate treatment, management, and patient education can be rendered.For the archaeological term, see Entoptic phenomena (archaeology).Įntoptic phenomena (from Ancient Greek ἐντός ( entós) 'within', and ὀπτικός ( optikós) 'visual') are visual effects whose source is within the human eye itself. Various types of visual phenomena, disturbances, and hallucinations are discussed. illusion or the visual system may produce images of things not really there, i.e. In addition, the visual system may process incoming sensory information in such a way that what is seen is perceived incorrectly, i.e. Such disruptions can be secondary to retinal and optic nerve disease, migraines associated with visual auras, and cerebrovascular and neurologic diseases they can also be side effects of certain drugs. In contrast, the visual system may be disrupted by various disorders and pathologic processes, which can result in metamorphopsia, transient loss of vision, and positive scotomas. ![]() ![]() Visual images produced by the intrinsic components of the eyes are often normal and are known as entoptic phenomena. The visual system and its processing of sensory information can be affected in a variety of ways that may be either normal or associated with numerous disorders and diseases.
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