Floaters and flashes that appear suddenly may signal detached retina, a serious eye problem.
Nearly everyone experiences floaters—small dots, lines, clouds, or “cobwebs” across the visual field—from time to time. This phenomenon is caused by shadows cast on the retina by microscopic structures within the vitreous humor (a thick, gel-like substance that fills the back of the eyeball behind the lens). Seeing flashes of light, which occurs when this fluid shifts, is another common ocular phenomenon.
In most cases, flashes and floaters are harmless and temporary, though they can be frequent and annoying. Sometimes, though, they indicate that the retina (the innermost layer of the eye that consists of light-sensitive nerve tissue) is tearing or in danger of detaching from the underlying layers of the eyeball. Detached retina may be a medical emergency that can result in blindness, but prompt treatment generally preserves vision.
How the Retina Detaches
Vitreous humor is a gelatinous fluid that adheres to the retina and fills most of the space inside the eye. As we age, the fluid gradually liquifies and becomes more mobile. Eventually, the vitreous humor begins to shift within the eye. Sometimes, this movement prompts the posterior surface of the vitreous to slide or pull away from the retina, a condition called posterior vitreous detachment (PVD).
PVD develops in 10% of adults by age 50 and in two thirds of those age 70 and older. In most instances it causes no problems. But sometimes the vitreous humor remains adherent to the retina in some areas; as it pulls away, it can tear the retina. Tears are not necessarily harmful, but they may permit fluid to collect underneath the retina. If the fluid spreads, the retina may peel away and detach from the back of the eye—a so-called detached retina.
Who’s At Risk for Detached Retina
Detached retina is a serious complication associated with cataract surgery. The problem develops in up to 1% to 2% of those who have a cataract removed, about half the time within a year of surgery. People who are severely nearsighted are also at increased risk, possibly because the elongated eyeball characteristic of the condition stretches and weakens the retina.
Additional risk factors include a personal or family history of detached retina, other eye problems (such as lattice degeneration, which causes retinal thinning), and eye trauma. People with diabetes are vulnerable to another, less common mechanism of retinal detachment related to the formation of scar tissue within the eye.
When To Worry That You Might Have a Detached Retina
Retinal tears are not painful, and symptoms may vary. Symptoms that do occur often appear in only one eye at a time and may develop either gradually or suddenly. The most distinctive clue of a detached retina is a shower of hundreds or thousands of little black dots across the field of vision, which may signal a hemorrhage caused by tearing across a blood vessel. Floaters or sudden flashes of white light also are characteristic of a detached retina. If the retina detaches, it may seem that a dark curtain or shade is spreading across the visual field.
Prompt evaluation by an ophthalmologist is necessary if you experience a shower of dots or a curtain spreading across the visual field; new unexplained blurred vision; or an unusually high number of floaters or intensity of light flashes. Call your eye doctor and do as he or she advises. If you don’t have an eye doctor and can’t locate one, you can go to an emergency room. Not all hospitals provide emergency eye care on site, however, so calling the hospital first may help you locate an appropriate facility.
Treating a Tear or Detached Retina
Numerous procedures may be used to treat retinal tearing and detachment, depending on their extent and location. In certain cases, small holes in the retina require no treatment. In others, combinations of more than one surgical approach may be required. Many are performed on an outpatient basis. The amount of vision restored and preserved with all procedures is greater if the macula is still attached—but even if the prognosis is poor, treatment usually is still advisable.
After treatment for a detached retina, medication can be prescribed to ease any pain. For the first few days following surgery, physical activity is usually restricted, although reading, writing, and watching television are generally possible soon after surgery. Improvement of vision in the affected eye may take weeks or months.
The chances of reattaching the retina are high for all types of retinal detachment surgery for uncomplicated cases, as more than 90% of retinal detachments can be repaired. The actual amount of vision restored, however, can vary greatly. A great advantage of the available techniques—laser therapy, cryotherapy, scleral buckling, vitrectomy, and pneumatic retinopexy—is that if one fails, another can be undertaken immediately or in a matter of days.
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Posted in Vision on April 20, 2006
Reviewed July 2009
