What Are Floaters?
As their name implies, floaters are usually small, black shapes that look like spots, squiggles, or threads, and "float about" in one's vision. They generally move as the eyes move, and are most noticeable against a plain bright background, such as a white or light-colored wall.
What Causes Floaters?
There are a number of conditions and changes within the eye that can cause floaters:
Changes in the vitreous: The inside of the back part of the eye is filled with a jelly-like substance called vitreous. The vitreous is attached to the retina, which is the thin, light-sensitive tissue that lines the inside surface of the eye. Much like the film of a camera, cells in the retina convert incoming light into electrical impulses. These electrical impulses are carried by the optic nerve to the brain, which finally interprets them as visual images.
As an individual ages, the jelly-like vitreous becomes more liquefied and areas of the vitreous can condense and acquire a "stringy" consistency. These strings or strands of vitreous can be perceived as floaters.
Posterior vitreous detachment (PVD): As the vitreous liquefies, it also shrinks and pulls away from the retina. This process is called a vitreous detachment. Many people develop posterior vitreous detachments and never experience symptoms, whereas others may notice new floaters. In general, a vitreous detachment is not considered an ocular emergency.
Retinal tear or detachment: In some cases, as the vitreous is peeling away from the retina and detaching, it can pull so hard in areas of firm attachment that it tears the retina. Therefore, any person with a PVD should have a careful retinal exam to rule out an associated tear. As the retina tears, a retinal vessel may be torn or damaged, leaking blood into the vitreous. This blood, called a vitreous hemorrhage, may also produce floaters.
A tear in the retina is of great concern, because it can extend and allow fluid to enter through the tear and separate the retina from the underlying tissue. To picture how this happens, imagine cutting a hole in a carpet and running a water hose into the hole. The carpet will rise up as it separates from the underlying floor. Retinal detachments lead to vision loss and are considered an ocular emergency.
Anyone can develop a retinal tear and detachment, but they are more likely to occur in persons who are nearsighted, older, have recently undergone cataract surgery, or have sustained a trauma to the eyes.
Vitreous hemorrhage: In addition to retinal tears, other conditions that result in bleeding into the vitreous, such as proliferative diabetic retinopathy, can produce floaters as well as decreased vision.
Inflammation: Less commonly, some types of inflammatory conditions of the eye, called uveitis, can lead to floaters.
What Should You Do if You Notice Floaters?
Anyone who notices new floaters should undergo a dilated eye examination by an ophthalmologist. The ophthalmologist may use a Q-tip or small instrument to push gently on the eye to look at the far edges of the retina not visible through a routine examination.
Any patient with a prior history of floaters who notices a new shower of floaters, flashing lights, or a curtain or shade "coming down over one eye" should undergo a prompt eye examination. These may be signs of a retinal detachment, or of a tear that can lead to retinal detachment. A retinal detachment requires prompt evaluation and treatment.
How Are Floaters Treated?
In all cases, the underlying cause of the floaters should be treated. The underlying cause for any inflammation or bleeding should be identified and treated accordingly.
If the floaters are due to changes in the vitreous or to posterior vitreous detachment, no intervention is necessary. A dilated eye examination should be performed to rule out an associated tear or detachment. In addition, many eye doctors may perform a follow-up exam in several weeks to confirm that a new tear or break has not developed in the retina. Over time, the floaters may decrease, and in many cases, the brain learns to ignore these floaters.
Retinal tears usually require treatment, including cryotherapy (cold therapy) or laser therapy to seal the tears. The cryotherapy probe is placed on the outside surface of the eye, directly over the area of the retinal tear. In laser therapy, a laser is directed into the eye and is focused on the area of the retinal tear.
Retinal detachments require cryotherapy or laser therapy to seal any breaks, as well as pneumatic retinopexy. Pneumatic retinopexy involves injection of air or a gas bubble into the back of the eye. The bubble expands and seals the tear and the surrounding retina to prevent additional fluid from collecting under the retina. The fluid already present under the retina is slowly pumped out by cells in the retina, allowing the retina to reattach.
Based on the location of the retinal tear, the patient may have to maintain his or her head in a certain position to keep the bubble in the right location—for example, face-down positioning, or sleeping on one side or the other. Patients with a gas bubble in the eye should not fly or dive, since pressure changes in either situation can result in expansion of the gas and endanger the eye. Over the course of several weeks, the gas bubble is replaced gradually by fluid created by the eye.
Retinal detachments may also require scleral buckle surgery or vitrectomy. In scleral buckle surgery, a buckle (a piece of silicone rubber) is sewn to the sclera (the coating of fibrous tissue that covers the white part of the eye) to indent it and relieve traction or pulling from the vitreous on the retina. This surgery is performed entirely outside the eye. The buckle remains in place after the conclusion of the surgery.
In vitrectomy, the vitreous is removed to relieve traction or pulling from the vitreous on the retina. Laser may be applied during the surgery, and pneumatic retinopexy (see above) can help flatten the retina and treat the detachment. Some cases of retinal detachment may require both vitrectomy and scleral buckle surgery.
In rare cases, a vitrectomy can be considered if floaters are causing significant visual symptoms. However, it is important to weigh the risks versus benefits of such a procedure.
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