Flashes and Floaters
Allen C. Ho, M.D. 

Definition Flashes of light and floaters are common ocular symptoms of benign floaters, a posterior vitreous detachment or occasionally, symptoms of a retinal tear or retinal detachment.

Causes of flashes and floaters

The back of the eye is filled with a jelly-like substance called the vitreous. In childhood, the vitreous has a thicker consistency, similar to that of jelly, and is attached to the retina which forms the inside wall of the eye. As a person ages, the vitreous becomes increasingly more liquid and begins to collapse in on itself and pull away from the inside walls of the eye. This process is known as posterior vitreous detachemtent, and usually occurs gradually over the course of several weeks or months. The areas of collapsed vitreous are then filled in with eye fluid, called aqueous, which is constantly being produced by the front part of the eye. Sometimes, small parts of the collapsed vitreous become visible to the eye. These can be perceived as small floaters which drift through the field of vision as the eye moves.

Occasionally, the process of posterior vitreous detachment is much more rapid. In these cases, flashes of light can be perceived as the vitreous tugs on small areas of the retina, where the vitreous is partially attached. Uncommonly, a small tear occurs in the retina in the spot where the vitreous is detaching from it. If the tear involves a blood vessel, a sudden shower of black floaters can be perceived in addition to flashes of light. A small retinal tear may occasionally heal on its own. However, eye fluid can sometimes dissect under the tear and cause the retina to detach from the inside wall of the eye, similar to wallpaper pealing off a wall if water is poured behind it.

Symptoms (What you may experience if you have a vitreous detachement, retinal tear or retinal detachment):

Floaters are an extremely common ocular condition and are benign in the vast majority of people who experience them. Even young individuals can notice floaters, especially when looking at bright lights. Floaters usually appear as small, spider-web like wisps that dance across the field of vision. Sometimes they appear as small rings or occasionally just small dots. If the floaters are fairly limited in number and are not rapidly increasing in size or number over a few hours or days, the are usually not a cause for concern.

However, floaters that are new or are increasing in size and number should be examined by an eye doctor. Typically, new floaters are just symptoms of a posterior vitreous detachment. Occasionally, though, they are symptoms of a retina tear or detachment. A shower of new floaters, which may appear as a “swarm of flies” in the field of vision appearing rapidly over a few minutes or hours may indicate bleeding into the eye from a torn blood vessel. If you have any concern about floaters, it is always appropriate to have your eye doctor examine them to make sure they are benign.

Flashes of light are less common than floaters. Typically they appear as a few sparks, localized in one part of the field of vision. They usually last only a few seconds, though may recur a several points over a few days in the same area of vision. Occasionally, a shower of sparks is perceived, indicating a much larger area of traction on the retina is occurring.

In the case of a retinal detachment, the vision may also be notably decreased. Usually this starts with the perception of a gauzy veil or cloud appearing in the edge of the visual field. This may stay relatively stable, or may slowly move towards the center of vision. If you perceive these symptoms, you should alert your eye doctor right away.

Examination for flashes and floaters:

Tests you may have at the doctor’s office:

To determine if the flashes and floaters you are experiencing are benign or related to a posterior vitreous detachment, retinal tear or retinal detachment, your eye doctor will perform an eye evaluation. Your visual acuity will be measured with an eye chart. Other tests may include eye pressure measurement, pupil testing, a peripheral vision check and range-of-motion testing of the eye muscles. Your doctor will perform a slit lamp examination to examine the front part of the eye. Your eyes will also be dilated to help the doctor view the vitreous and retina in the back part of the eye. Your doctor may also use a special contact lens or apply pressure to the walls of the eye with a small probe in order to better visualize the parts of the retina in the periphery of the eye.

What your doctor sees in your eye during your exam for flashes and floaters:

In the case of benign floaters and in a posterior vitreous detachment, your doctor may actually see small opacities in the vitreous. However, sometimes no opacity is seen at all. Your doctor will examine your eye to make sure no other problems are present, such as a tear in the retina, and will reassure you that all is well. In the case of a retinal tear or retinal detachment, your doctor may see some blood in the vitreous, which may have caused the floaters you perceived. A small tear in the retina may also be seen, or an area of retinal detachment, which appears like a blister on the retina.

Treatment of Flashes and Floaters:

Benign floaters:

If your doctor has examined you and determined that your floaters are benign, no treatment is needed. Your doctor may ask you to schedule another visit in a month or two for a repeat examination to ensure that your eye is stable.

Posterior vitreous detachment:

If your doctor has examined you and determined that your floaters are related to a posterior vitreous detachment, no treatment is usually needed. A vitreous detachment may slowly evolve over several weeks, during which time you may continue to experience flashes and floaters. Your doctor may ask you to schedule another visit in a month or two for a repeat examination to determine if the vitreous detachment is completed or is still evolving. You should alert your doctor if you experience a significant increase in the number or size of flashes and floaters during this time.

Retinal tear or Retinal Detachment:

If your doctor has examined you and determined that your floaters are related to a retinal tear or retinal detachment, typically treatment will be needed. Laser can be used to help a retinal tear scar down and prevent it from progressing to a retinal detachment. In the case of a retinal detachment, surgery is usually required to repair the problem. Retinal detachment repair surgery is typically performed on an outpatient basis. The procedure itself usually takes about 1-2 hours to complete. Your doctor will typically see you 1 day to make sure the eye is healing well and that there are no signs of infection. You will typically be seen several times over the next several months to make sure the retina is staying attached after the surgery. Retinal detachment surgery is generally very safe. Advanced surgical techniques and equipment, plus the high level of skill eye surgeons acquire during training, have greatly decreased severe complications that occur during eye surgery such as this.

Prognosis (Flashes and Floaters affect vision over the long-term):

The prognosis for small, benign floaters is excellent and usually causes not change in the vision. Larger floaters like those associated with a posterior vitreous detachment, however, may cause bothersome visual symptoms as the float through the visual field. Typically, though, larger floaters will settle down towards the bottom of the eye with time and be less noticeable. In extreme cases where larger floaters do not settle down and cause decrease of the central vision, surgery can be performed to remove them. However, the risks of surgery usually outweigh the benefits in the case of smaller floaters.

Flashes of light tend to resolve after the vitreous completely detaches from the retina. Typically this process is completed after a few weeks.

If a retinal tear occurs, the prognosis for maintaining excellent vision is usually very good if the tear is appropriately treated and does not progress to a retinal detachment.

In the case of a retinal detachment, if it is caught early and limited to the edge of vision, usually very little noticeable vision is lost. However, if the detachment progresses to involve the center of vision, permanent visual loss usually results. If the detachment can be surgically repaired soon, typically only a few lines of vision are lost. However, in the case of large retinal detachments involving the center of vision which are present for a few weeks or months, far less vision is usually recoverable after surgical repair of the detachment.

Prevention of flashes and floaters:

While benign floaters and posterior vitreous detachment are usually natural processes that can’t be prevented, several factors are known to increase the risk of retinal detachment. These risks include having significant eye or head trauma, which can cause sudden sloshing of the vitreous and the formation of a retinal tear; a first degree relative with a history of retinal detachment; high levels of myopia (nearsightedness); and/or a history of prior eye surgery.

Page Topics Include: flashes and floaters, retinal detachment, treatment for flashes and floaters, causes of flashes and floaters