They are also called Muscae volitantes (from the Latin, meaning “flying flies”), or mouches volantes (from the French). They may appear as spots, threads, which float slowly before the observer’s eyes. The common type of floater, which is present in most people’s eyes, is due to degenerative changes of the vitreous humour. The perception of floaters is known as myodesopsia, or less commonly as myiodeopsia, myiodesopsia, or myodeopsia
Non-Worrisome Floaters
Many people occasionally see some floating material in their vision. This may appear as a dot, a translucent short string, or a ”tadpole”. These floaters are often seen only under bright lighting circumstances, for example, against snow or a bright sky or a white ceiling. Some patients first notice them when looking through a microscope or binoculars. Most such floaters are visible again under similar lighting conditions. These non-worrisome floaters represent flecks of material floating in a liquid pocket within the vitreous jelly-bag in the back of the eye.
Causes
Posterior vitreous separation produces another kind of floater, which is moderately worrisome. Posterior vitreous separation is a rather common event, and is caused by the shrinkage of the vitreous. As the vitreous shrinks, it often pulls away from the back of the eye, and this is posterior vitreous separation. Shrinkage of the vitreous is a natural process of aging, and about 50% of eyes by age 60 have gone through posterior vitreous separation. The sudden appearance of floaters in one eye is the primary symptom of posterior vitreous separation. These floaters are usually described as a cobweb, a comma or a circle, and usually appear in the vision slightly to the side from where one looks. Sometimes a posterior vitreous separation is accompanied by flashes of light off to the side in the vision of the affected eye. Occasionally, these flashes precede the actual posterior vitreous separation by several days or even weeks. Sometimes they last on an occasional basis for months afterward.
Apart from the nuisance of experiencing floaters, the problem with posterior vitreous separation is that between 3% and 10% of the time the retina is torn in the process. This happens when points on the vitreous are attached to the retina and pull on it as the vitreous shrinks and pulls away from the retina. About 50% of the eyes that have a retinal tear will, if not treated, go on to develop a retinal detachment. If this is going to occur, it usually occurs during the first 6 weeks from the onset of floaters. Suddenly seeing a large number of tiny dots in one’s vision, especially along with other floaters, increases the concern. These dots are red blood corpuscles and imply that either a blood vessel on the retina has been tweaked or the retina itself has been torn. The likelihood of finding a retinal tear in the presence of these ”dots” is about 50%, increased from the 3-10% chance when they are not present.
Prevention
At the sudden onset of floaters, it would be wise to see a doctor within a few days and avoid heavy or jarring exercise in the meantime. If you experience ”dots”, it is especially important that you see an eye specialist as soon as possible so they can detect and treat any possible retinal tears and avoid retinal detachment. In the examination, the doctor will dilate your eyes with eye drops. The eye is examined with the patient lying down while the doctor uses an indirect ophthalmoscope and a hand-held lens. A small probe called a scleral depressor (similar to the tongue depressors used by your family doctor or internist) is used to press on the eyeball through the eyelid in order to bring into view the part of the retina in which the tears are usually found. After the examination, if a tear is not discovered, it is not likely that one will develop later. It is not, however, impossible. Symptoms to be on the alert for are:
1. A new mess of floaters, especially if accompanied by a large number of little dots.
2. A shade or shadow covering up or severely disturbing part of the side (or up or down) vision of the affected eye. It does not hurt to check your peripheral vision briefly on a daily basis, especially during the 6 to 8 week “danger period“. You can do this by closing the eye you are not checking, picking an object to look at on the opposite wall straight ahead, and presenting your fingers off to the side, above, and below, to make sure that the area of the side vision that you ought to be able to see is still working.
If a retinal tear is found, either cryotherapy or laser will be recommended to seal the area around the retinal tear to prevent a retinal detachment. These are both outpatient procedures involving minimal discomfort and are often performed on the same day that the retinal tear is discovered. Such treatment reduces the likelihood of a retinal tear progressing to a retinal detachment from 50% down to 2% or 3%.
What Happens to the Floaters?
In most eyes, the floaters will ”lighten up” over a period of several weeks to several months as the particles that cause the floaters in the vitreous are naturally absorbed back into the blood stream. Most patients get quite used to any floaters that might remain, noticing them only when asked to specifically look for them.
Will this Happen Again?
Posterior vitreous separation is ordinarily an all or nothing phenomenon. Exceptions exist, but usually a completed posterior vitreous separation that has been present for 2 or 3 months without trouble is considered protective against retinal detachment. What is Not a Floater? Shimmering lights, which obscure a portion of the vision, gradually developing and subsiding over 15 minutes to an hour and usually present to some extent in both eyes are not floaters. Most commonly these symptoms are related to migraine, even though they sometimes occur without headache.