Floaters are deposits of various size, shape, consistency,
refractive index, and
motility within the
eye's
vitreous humour, which is normally transparent. At a young age, the vitreous is transparent, but as one ages, imperfections gradually develop. The common type of floater, which is present in most persons' eyes, is due to degenerative changes of the vitreous humour. The
perception of floaters is known as
myodesopsia, or less commonly as
myodaeopsia,
myiodeopsia,
myiodesopsia. They are also called
Muscae volitantes (Latin: "flying flies"), or
mouches volantes (from the French). Floaters are visible because of the shadows they cast on the
retina or refraction of the light that passes through them, and can appear alone or together with several others in one's
visual field. They may appear as spots, threads, or fragments of cobwebs, which float slowly before the observer's eyes. As these objects exist within the eye itself, they are not
optical illusions but are
entoptic phenomena.
