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 gel-bag in the back of the eye.
Posterior vitreous detachment (PVD) produces another kind of floater, which is moderately worrisome. PVD is a rather common event. About 50% of eyes by age 60 have gone through this process. The sudden appearance of new floaters in one eye is the primary symptom of a PVD. 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 PVD 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.
Apart from the nuisance of experiencing new floaters, the problem with a PVD is that about 10% of the time the retina (the “Saran Wrap” thin membrane suctioned up against the inside back part of the eyeball –if your eye was a camera, it would be the film) 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. (See Detached and Torn Retina section) Suddenly seeing a large number of tiny dots in one’s vision, especially along with other floaters and flashes, increases the concern. These dots are either red blood cells or freed retinal cells implying 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 85%, increased from 3% to 15% chance when they are not present. Since almost all of the retinal detachments that result from tears occurring from a PVD develop within 6 weeks of the onset of floaters, it follows that if one has had symptoms of a PVD for more than 6-8 weeks, one has been through the period of major worry of retinal detachment.
A PVD can also cause microtrauma to the surface of the retina causing a scar to form called an epiretinal membrane (see Macular Pucker/Epiretinal Membrane Section) which can distort vision.
While most people see a few spots on occasion, they can occur more frequently and become more noticeable with age when a posterior vitreous detachment occurs. More rare causes of floaters include infection, inflammation, hemorrhage, retinal tears, or eye injury.
Specks and threadlike strands that drift across a person’s field of vision are the floaters. When you try to look at them, they generally float away. Floaters are most visible when looking at bright objects, such as white paper or blue skies. A new floater, flashes, or shower of floaters is worrisome for a PVD and/or retinal tear. 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.) If the floaters are still bothersome after about 6 months, a simple surgery can be performed to remove them permanently.
Flashes and floaters are not generally a serious condition needing treatment, but they can be symptoms of vitreous or retinal detachment. If one has experienced floaters suggesting a PVD, 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. 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 or 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.
Surgery for Removal of Floaters
The procedure is done under local anesthetic as an outpatient in much the same way modern cataract surgery is performed. After the placement of the local anesthetic, the patient is positioned under a large microscope. Three tiny wounds are made in the front, white part of the eye a few millimeters away from the colored part of the eye. During the procedure, the eye is maintained in its normal shape by the infusion of fluid. The surgeon views the process using an operating microscope and looking down through the dilated pupil. Light is provided in the eye by a fiber-optic light pipe. Instruments are introduced with which the vitreous gel is removed. Sometimes there is a very subtle, but important layer of vitreous material still lying on the macula which is removed by special techniques. If a person has had cataract surgery, removal of the posterior lens capsule is also performed to prevent needing another procedure in the future that may produce new floaters. The instruments are then removed from the eye, and the tiny wounds usually self-seal but sometimes are sewn closed. The patient wears a patch and shield over the eye for the first 24 hours. The amount of discomfort experienced following the surgery is usually quite minimal. Most vitrectomies for floaters require less than an hour of actual operating time but may involve several hours overall for registration and anesthesia.
The visual results of such surgery are very satisfying with complete resolution of symptoms in over 93% of eyes. For those who still have some symptoms remaining, they are usually very mild. Repeat surgery, if needed, relieves residual floaters.
Vitrectomy provides a definitive cure to floaters, although the surgery is not without risk, albeit quite minimal. If the patient hasn’t had cataract surgery yet, there is a high likelihood that in the next several years a cataract will develop in the operated eye. Such cataracts are removed in the same way as ordinary cataracts as an outpatient under local anesthetic. All the other risks are much less frequent. There is a published 1-2% risk of a retinal detachment developing following surgery for floaters. More than 90% of these detachments are fixable, but require further surgery for the repair. There is a 1 in 10,000 risk of a devastating intraocular infection. There are also lesser risks of transient glaucoma, vitreous and retinal hemorrhage, and macular edema. Modern 25-gauge instrumentation and techniques have helped to greatly reduce the risks of these surgical complications.
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 migraines, even though they sometimes occur without a headache.