Floaters or eye floaters are sometimes visible deposits within the eye's vitreous humour ("the vitreous"), which is normally transparent, or between the vitreous and retina. Each floater can be measured by its size, shape, consistency, refractive index, and motility. They are also called "muscae volitantes" (Latin for 'flying flies'), or "mouches volantes" (from the same phrase in French). The vitreous usually starts out transparent, but imperfections may gradually develop as one ages. The common type of floater, present in most people's eyes, is due to these degenerative changes of the vitreous. The perception of floaters, which may be annoying or problematic to some people, is known as myodesopsia, or, less commonly, as "myodaeopsia", "myiodeopsia", or "myiodesopsia". It is not often treated, except in severe cases, where vitrectomy (surgery), laser vitreolysis, and medication may be effective.