Floater - Description

Description

Floaters are suspended in the vitreous humour, the thick fluid or gel that fills the eye. Thus, they generally follow the rapid motions of the eye, while drifting slowly within the fluid. 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 since floaters follow the motion of the eye, remaining to the side of the direction of gaze. Floaters 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 due to neural adaptation. This stabilization is often interrupted by floaters, especially when they tend to remain visible.

Floaters are particularly noticeable when looking at a blank surface or an open monochromatic space, such as blue sky. Despite the name "floaters", 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 floaters less blurry and easier to see.

Floaters are essentially changeless, and the most prominent continue to be seen in the field of vision for a lifetime. They are not uncommon, and do not cause serious problems for most people; 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 floaters in the UK. However, floaters are more than a nuisance and a distraction to those with severe cases, especially if the spots seem to constantly 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. Floaters 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 people who are troubled by floaters; they can also become a problem to younger people, especially if they are myopic. They are also common after cataract operations or after trauma. In some cases, floaters are congenital.

Floaters are able to catch and refract light in ways that somewhat blur vision temporarily until the floater moves to a different area. Often they trick people who are troubled by floaters into thinking they see something out of the corner of their eye that really is not there. Most people come to terms with the problem, after a time, and learn to ignore their floaters. For people with severe floaters it is nearly impossible to completely ignore the large masses that constantly stay within almost direct view.

Floaters have been reported in patients as young as 3. Floaters in teenage patients and young adults are usually harder to treat. For people in this age group, the floater that is seen usually looks like a kind of crystal (translucent) worm/web/cell. These particular floaters aren't really floaters in a technical sense as they aren't found in the vitreous humour, instead they are found right on top of the retina in the premacular bursa. Very little is known about this region, and it only becomes distinct after the vitreous detaches from the retina at later stages of life. Due to their microscopic size they cannot be seen by professional doctors. They only appear as big as they do because of their proximity to the retina. This type of floater is still described occasionally in the third decade and very rarely occur in the 40 or older population.