<unk> s are from objects in pockets of liquid within the vitreous humour, the thick fluid or gel that fills the eye, or between the vitreous and the retina. The vitreous humour, or vitreous body, is a jelly-like, transparent substance that fills the majority of the eye. It lies within the vitreous chamber behind the lens, and is one of the four optical components of the eye. Thus,<unk> s follow the rapid motions of the eye, while drifting slowly within the pocket of liquid. When they are first noticed, the natural reaction is to attempt to look directly at them. However, attempting to shift one's gaze toward them can be difficult because<unk> s follow the motion of the eye, remaining to the side of the direction of gaze.<unk> s are, in fact, visible only because they do not remain perfectly fixed within the eye. Although the blood vessels of the eye also obstruct light, they are invisible under normal circumstances because they are fixed in location relative to the retina, and the brain "tunes out" stabilized images through neural adaptation.<unk> s are particularly noticeable when looking at a blank surface or an open monochromatic space, such as blue sky. Despite the name<unk> s", many of these specks have a tendency to sink toward the bottom of the eyeball, in whichever way the eyeball is oriented; the supine position (looking up or lying back) tends to concentrate them near the fovea, which is the center of gaze, while the textureless and evenly lit sky forms an ideal background against which to view them. The brightness of the daytime sky also causes the eyes' pupils to contract, reducing the aperture, which makes<unk> s less blurry and easier to see.<unk> s present at birth usually remain lifelong, while those that appear later may disappear within weeks or months. They are not uncommon, and do not cause serious problems for most persons; they represent one of the most common presentations to hospital eye services. A survey of optometrists in 2002 suggested that an average of 14 patients per month per optometrist presented with symptoms of<unk> s in the UK. However,<unk> s are more than a nuisance and a distraction to those with severe cases, especially if the spots seem constantly to drift through the field of vision. The shapes are shadows projected onto the retina by tiny structures of protein or other cell debris discarded over the years and trapped in the vitreous humour or between the vitreous and retina.<unk> s can even be seen when the eyes are closed on especially bright days, when sufficient light penetrates the eyelids to cast the shadows. It is not, however, only elderly persons who are troubled by<unk> s; they can also become a problem to younger people, especially if they are myopic. They are also common after cataract operations or after trauma.<unk> s are able to catch and refract light in ways that somewhat blur vision temporarily until the<unk>  moves to a different area. Often they trick persons who are troubled by<unk> s into thinking they see something out of the corner of their eye that really is not there. Most persons come to terms with the problem, after a time, and learn to ignore their<unk> s. For persons with severe<unk> s it is nearly impossible to ignore completely the large masses that constantly stay within almost direct view.
Floater
Boil
BoRit Asbestos
Drustbed
Straw 
Dream
Snake
Wart