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, or 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.
- When the eye has imperfect sight the mind not only distorts what the eye sees, but it imagines that it sees things that do not exist. Among illusions of this sort are the floating specks which so often appear before the eyes when the sight is imperfect, and even when it is ordinarily very good. These specks are known scientifically as "muscæ volitantes," or "flying flies," and although they are of no real importance, being symptoms of nothing except mental strain, they have attracted so much attention.
- William Bates, Perfect Eyesight Without Glasses, 1920
- At first the amoebae look like muscae volitantes, those curled moving spots you seem to see in your eyes when you stare at a distant wall. Then I see the amoebae as drops of water congealed, blusish, translucent, like chips of sky in the bowl.
- Oh, squiggly line in my eye fluid. I see you there lurking on the periphery of my vision. But when I try to look at you, you scurry away. Are you shy, squiggly line? Why only when I ignore you, do you return to the center of my eye? Oh, squiggly line, it's alright, you are forgiven.
- A common experience... is for a person who has some ocular trouble that impairs his vision to become suddenly aware of the so-called mouches volantes in his visual field, although the causes of this phenomenon have been there in the vitreous humour all his life. Yet now he will be firmly persuaded that these corpuscles have developed as the result of his ocular ailment, although the truth simply is that, owing to his ailment, the patient has been paying more attention to visual phenomena.""
- They could have done the same thing, alone, in the back yard, seeing the shapes swimming in the sky. I forget how old I was when I asked somebody about it, and I was told that those wonderful gliding changing spots were imperfections in the fluid of my eye-ball, that what I was seeing was in my eye. In your eye! For so long, for a child's years, the sky was full of wonder, these shapes were in the sky, the sky was full of transparent things that swooped and swam. They were almost invisible, and, I thought, almost bodiless, they were there, but you could go right through them, they were animals that lived in the air. You see, we didn't go around talking about things like this. It's only now, when I am grown up and know everything, that I talk about this.