Flashes & Floaters


Flashes and floaters are very common, usually harmless, and become more frequent as we age. In rare cases, an eye exam may reveal a more serious problem. Be sure to schedule your exam every year or two and inform your examiner if you’re experiencing flashes or floaters.

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It is normal to sometimes see small specks, strands, webs or clouds moving in our field of vision, most often when looking at a plain background, like a blank wall or blue sky. The most common type are those annoying little black specks which seem to dart away – just out of sight – as you look for them. These are called floaters.

Floaters are tiny clumps of cells suspended inside the vitreous – although, what you actually see are shadows of the floaters, cast on the retina. Because they are inside the eyes, they move when you try to take a closer look at them.

Imagine clear fiberglass strands submerged in water and illuminated by a flashlight. Although both the water and the strands are clear they have different optical characteristics, and the strands will cast a shadow. Imagine clear fiberglass strands submerged in water and illuminated by a flashlight. Although both the water and the strands are clear they have different optical characteristics, and the strands will cast a shadow.

Strand-like floaters are usually just mucous threads floating in the tear layer on the cornea. Since tears are made of oil, water and mucous, at times these three ingredients mix in a way that forms floating globules of oil or mucous. Shadows of individual blood cells darting through the blood vessels in the back of the eye are another common sight.

Floaters occur more often for people who are:

  • Nearsighted
  • Cataract patients
  • Recipients of YAG laser surgery
  • Experiencing inflammation inside the eye
  • Pregnant

For most people, floaters are harmless and part of the natural aging process. Over time, the vitreous humor (the jelly in the back part of the eye) thickens into tiny clumps, and floaters are the result. It is common for floaters to appear and diminish in their appearance over time. Any exceptions to these conditions might be a sign of something more serious:

Serious floaters

Occasionally floaters are warning signs of imminent danger or damage occurring somewhere in the eye. The rapid onset of large and numerous floaters may signal an impending retinal detachment or indicate an internal hemorrhage of blood from a leaking vessel. Rare in the under 50 crowd, these incidences become more common by age 70 or so.

Floaters that are considered emergencies and requiring immediate medical attention usually can be differentiated by some important factors:

  1. They appear suddenly
  2. Are accompanied by visual field defects including flashes of light and areas of vision loss (as if a dark curtain passes in front of the eyes)
  3. Appear numerous and/or large
  4. Are associated with a trauma or a blow to the eyes or head
  5. Appears as if they are increasing, not decreasing in numbers (and annoyance) over a short period of time, often minutes or hours


These apparent bursts of light can be small, bright pinpoint objects, sparkles, zigzag patterns, or even appear like a lightening storm. The phenomena have one root cause: non-optical stimulation of the photoreceptors of the retina. These flashes occur more often in older people as the vitreous humor thickens and pulls on the light-sensitive retina, and may be a warning sign of a detached retina. Flashes are also known to occur after a blow to the head, referred to as seeing stars.

When flashes of light appear in both eyes as jagged lines or heat waves, often lasting 10-20 minutes, they are most likely caused by a spasm of blood vessels in the brain. If a headache follows the flashes, it is called a migraine headache; however, a migraine can occur without the headache, in which case the flashes are called an ophthalmic migraine.

Serious flashes

There are differences between ophthalmic migraines and the more serious embolism event (a blood clot) or retinal detachment:

  1. Flashes associated with ophthalmic migraines almost always resolve within a few minutes, and almost never more than about twenty minutes, rarely up to 40 minutes.
  2. Flashes caused by embolisms or retinal detachment, don’t stop and typically become more noticeable with time, often including visual areas of gray or dark blind spots.

Always consult with an eye doctor when visual disturbances indicate a potentially serious problem. Very often these are warning signs, which relate not only to eye problems, but also to other systemic pathology and disease: hypertension (high blood pressure), arteriosclerosis (hardening of the arteries), sickle cell disease, impending heart attack or stroke, or other serious conditions. Medical intervention and treatment can help prevent permanent and significant damage.

Any flashing light or visual disturbance that lasts more than twenty to forty minutes is considered an ocular emergency and requires prompt discussion with and probable examination by your eye doctor.

How it works

Most flashes and floaters are caused by age-related changes in the vitreous that fills the back of the eye.

When we are born, the vitreous has a consistency similar to very thick gelatin and is firmly attached to the retina. At that time, the vitreous contains microscopic clumps or strands of tissue-debris leftover from the eye’s prenatal development. These leftovers are embedded in the vitreous and cannot move around.

As we get older, the vitreous gradually becomes thinner or more watery. As we approach our twenties or thirties, the vitreous may be liquid enough to allow some of the clumps and strands to move around inside the eye. This material floating inside the eye can cast shadows on the retina, which are seen as small floating spots. If they exert a pulling effect on the retina, flashes of light may result.

After about age fifty-five, the vitreous gel usually becomes much more watery and we may experience the onset of larger, more bothersome floaters or flashes of light. Eventually, the aging vitreous may pull away from the retina altogether and shrink into a dense mass of gel in the middle of the eyeball, causing a vitreous detachment, which may in turn lead to a retinal detachment.


Using special instruments to look into your dilated eyes, Dr. Seibel can distinguish between harmless floaters and flashes and more serious retinal problems such as holes, tears or detachment.


There is no treatment. Flashes and floaters cannot be eliminated through surgery, laser treatment or medication. Over time, they will simply become less noticeable, as the brain adjusts to tune them out.

If you see new floaters suddenly, or eye floaters accompanied by flashes of light or peripheral vision loss, it could indicate serious conditions that require urgent medical attention. See your doctor immediately.

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