Flashes & 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 often are 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.
Posterior Vitreous Separation
Posterior vitreous separation produces another kind of a floater, which is moderately worrisome. Posterior vitreous separation is a rather common event. About 50% of eyes by age 60 have gone through this process. 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 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. Eventually, they subside.
What’s the Worry?
Apart from the nuisance of experiencing floaters, the problem with posterior vitreous separation is that between 3% and 10% of the time the retina (the Saran Wrap thin membrane suctioned up against the inside back part of the eyeball that acts a little like the film in your camera) is torn in the process. About 50 percent 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% to 10% chance when they are not present.
Since almost all of the retinal detachments that result from tears occurring from a posterior vitreous separation develop within 6 weeks of the onset of floaters, it follows that if one has had symptoms of a posterior vitreous separation for more than 6-8 weeks, one has been through the period of major worry of retinal detachment.
If one has experienced floaters suggesting a posterior vitreous separation, it is a good idea to be examined by an eye physician within a few days and to avoid heavy jarring exercise in the meantime. The proper examination involves dilating the pupil with eye drops (usually, but not always, both eyes are dilated). The eye is examined with the patient lying down using the indirect ophthalmoscope (which appears as a bright light on the examiner's forehead) and a hand-held lens. A small probe called a scleral depressor 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.
What to look for afterward?
If a tear is not discovered, it is not likely that one will develop later. However, it is not impossible. Symptoms that should cause one to return for re-examination are:
- A new mess of floaters, especially if accompanied by a large number of little dots.
- A shade or a 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 the peripheral (side) vision briefly on a daily basis, especially during the 6 to 8 week "danger period". This is accomplished by closing the other eye, picking an object to look at on the opposite wall straight ahead, and presenting one's fingers off to the side, and above and below, to make sure that the area of the side vision that you ought to be able to see is still working.
What about re-examination?
If there is no abrupt change in floaters and no shade or shadow develops, is it necessary to have a follow-up examination? Often a formal follow up examination is not necessary. However, if your eye physician detects any suspicious findings in the peripheral retina or if there are other particular risk factors in your personal or family ocular history, then a follow-up examination or a referral to a retinal specialist may be recommended.
What if a tear is found?
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 going on to a retinal detachment from 50% down to 2% or 3%.
What will happen to my floaters?
In most eyes, the floaters will "lighten up" over several weeks to many months. In addition, most patients eventually get quite used to the floaters that remain, noticing them only when asked to look for them. (Admittedly, this may not sound very likely right now, but it almost always comes to pass.)
Will this happen again?
Usually not. 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 (if one thinks to check the other eye) are not floaters. Most commonly these symptoms are related to migraine, even though they sometimes occur without headache.