muscae volitantes

   Also known as mouches volantes, floaters, eye floaters, vitreous floaters, flying gnats, and entopsia. Muscae volitantes is Latin for flying flies. Thetermisusedtodenotean* entoptic phenomenon consisting of out-of-focus black or greyish specks, spots, threads, or fragments of cobwebs, which move slowly across the visual field. Normally muscae volitantes tend to go unnoticed because their angular size is small, and they affect each eye differently. They can be seen best against a uniformly bright background and sometimes even better through a pinhole placed close to the eye. Pathophysiologically, muscae volitantes are associated with the presence of deposits of protein or other cell debris of varying size, shape, consistency, refractive index, and motility within the eye's vitreous humour, the shadows of which are projected upon the retina. They may be congenital or acquired in nature. In the latter case, they may be due to vitreoreti-nal disorders, to trauma, or simply to ageing. The perception of muscae volitantes is referred to as myodeopsia, myiodeopsia, myiodesopsia, or myodesopsia. Sometimes muscae volitantes lead the affected individual to perceive fleeting illusory images, called * passage hallucinations. It has been speculated that these may even act as * points de repère for the development of * complex visual hallucinations. As the British surgeon Walter Cooper Dendy (1794-1871) wrote in 1847, "Mus-cae volitantes are usually, though not always, substantial; i.e., depending on points or fibres in the axis of vision, on congestions,or varicose states of the vessels of the choroid or retina, or of atoms floating in the humours. These specks, which do not appear alike in the eyes of all, and the brilliant beams in the suffusio scintillans, so varied and so whimsical, might be readily moulded into human form by the imagination of an enthusiast or the feelings of the ghost-seer, who is usually morose and melancholy, in a state of longing for a ghost or a mystery." Muscae volitantes should not be confused with the * blue-field entoptic phenomenon.

   References

   Dendy, W.C. (1847). The philosophy of mystery. New York, NY: Harper & Brothers. Murakami, K, Jalkh, A.E., Avila, M.P., Trempe,

   C.L., Schepens, C.L. (1983). Vitreous floaters. Ophthalmology, 90, 1271-1276.