Posted on 01/28/2005 9:52:56 PM PST by neverdem
My introduction to floaters came on a sunny September afternoon in the orchard. I was high on a ladder picking Jonagold apples when I felt a pop in my left eye, followed by blurriness. I thought that maybe a branch had slapped across my glasses, dirtying the lens, and I went inside to clean it. But the blurriness - a sort of floating haze - persisted overnight.
After hearing the symptoms, my ophthalmologist, Dr. William Kirber, diagnosed a posterior vitreous detachment, one of several causes of floaters, sensations that many people describe as specks, bugs or cobwebs floating in their fields of vision. In 85 percent of cases, the floaters caused by posterior detachment are mere annoyances, but when they occur suddenly, immediate medical examination is essential.
The most common type of floater is caused by aging. Sitting directly between the lens and the retina is a cavity known as the vitreous or vitreous humor. Its outer boundary is defined by a crust like the skin of Jell-O. The function of the vitreous, which makes up four-fifths of the volume of the eye, is to give it its shape, to be a shock absorber in younger eyes and, some argue, to nourish the inner eye.
The vitreous cavity is filled with a clear, sticky gel that is 99 percent water. The balance consists of strands of a protein called collagen and acidic molecules. With aging, the molecules break down, releasing water that gathers in pockets. At the same time, strands of collagen, normally translucent, bunch into larger opaque fibrils or wispy sheaths.
It is these clumps of protein and water, of varying shape, meandering unpredictably within the vitreous cavity, that are the source of most floaters. As light passes through the vitreous, floaters cast annoying shadows on the retina, the eye's movie screen. Most adults experience this type of floater at some time.
Much less common is a second type, floaters caused by specks or globs of blood, the result of bleeding brought on by rips in the retina or as a complication of diabetes.
In each case, the brain almost always gets used to the floaters or they migrate out of view. The third kind of floater, however, caused by a posterior vitreous detachment, is far more likely to impair vision.
In posterior vitreous detachment, as the fluid from the degenerating vitreous gel moves between the skin of the vitreous and the retina, the vitreous separates from the retina, usually near the optic nerve. As the vitreous tears from the retina, a fragment of tissue remains attached to the receding vitreous.
Because the tissue is tethered to the vitreous, this fragment, known as Weiss's ring, sometimes remains in the central field of vision. Under the ophthalmologist's slit lamp, Weiss's ring resembles a blob of oil floating on water under a lattice of blood vessels. How disabling this vitreous detachment is depends on how far the vitreous peels from the retina.
Posterior vitreous detachments occur in fewer than 10 percent of people under 50, but in 60 percent of people over 70. In 10 to 15 percent of detachments, as the vitreous separates, it tears the retina, requiring immediate treatment, either with a laser or through surgery.
The question is, When are floaters alarming and when are they benign?
"Almost everyone has floaters," Dr. Jim Garrity, a Mayo Clinic ophthalmologist, stresses in a periodic lecture he offers for general practitioners. "It is the sudden onset of the tiny ones accompanied by flashes of light that you have to be concerned about."
Many ophthalmologists underrate floaters because they cannot be visualized precisely and because the potential complications from removing the vitreous, the only sure remedy, heavily outweigh the benefits, some experts say.
Dr. William Schiff, a retinal surgeon at Columbia and the lead author of a 2000 article in the journal Retina on vitreous removal to relieve disabling floaters, has called the surgery "eminently doable but universally discouraged." Surgical complications include the almost certain development of cataracts, bleeding and retinal detachment as the vitreous is peeled from the retina.
Still, in rare instances surgery is necessary.
Dr. Stanley Chang, chairman of ophthalmology at Columbia, says that in many cases eye doctors do not appreciate the effect floaters have on patients' lives.
In screening patients for surgery, Dr. Chang evaluates the floaters' impact on reading speed, the ability to read signs and newsprint, the ability to play sports and driving ease. He says he follows patients for a year to see if the surgery, which he performs only once every year or two, is really needed.
Dr. Chang sometimes refers patients to an article written by a retinal surgeon, Dr. Travis A. Meredith, about his own trials with floaters. "When patients say that their floaters are driving them crazy," Dr. Meredith confesses, "it is not such an exaggeration as I had imagined."
Although most ophthalmologists agree that floaters are almost always best left alone, they rank high on the list of patient complaints, and many eye surgeons offer a less drastic procedure, laser surgery, to break up the clumps. But a recent study found that in no cases were patients' symptoms completely alleviated by laser surgery. Dr. Chang and Dr. Schiff note that floater fragments that result from laser treatment are often no improvement over the floaters themselves.
It is not practical to relieve floaters by mechanically sucking out the vitreous contents, filtering it and returning it or a substitute fluid to the cavity, Dr. Chang explained. The obstacle, he said, is that vitreous gel appears to block oxygen from reaching the lens. Any disturbance of the vitreous is likely to bring on cataracts.
Thus, for the time being, the best candidates for surgery to relieve floaters are those who have already had cataracts removed.
A promising drug, just arriving on the market, may point the way to eventually treating disabling floaters more effectively. Vitrase, by ISTA Pharmaceuticals, is a natural enzyme made from ram testes that the company claims can induce the vitreous to separate from the retina, removing the floaters from the visual field.
At higher doses, Vitrase is said to liquefy the vitreous contents, making it possible to readily suck out the fluid. Dr. Chang's reservation about the drug is that, in addition to loosening vitreous material, excess dosing may also dissolve weak spots in the retina. If the dosing problem with Vitrase is resolved and a way is found to prevent vitreous intervention from inducing cataracts, disabling floaters may become a thing of the past.
In the meantime, Dr. Chang counsels people who suffer from floaters to alert their eye doctors to their problems before being fitted with corrective lenses. Especially with high prescriptions, floaters can obstruct parts of letters on the eye chart, making it harder to measure vision.
Good article, ND. BTTT!
FReepmail me if you want on or off my health and science ping list.
Bump for later. Great. So that's what those flashes of light are....
Very good article. I've had floaters since I was a teenager. Some are so strange that they are hard to describe. My eye doctor told me he would be a very rich man if he knew how to stop the progression [as we age].
In this case, that should be B*TT.
I've had them since my mid-40s. And that's been a while. My eye doctor said I would get used to them. He lied.
LOL!
I had a detached retina in 1996. Not fun. My sight has never been the same. Didn't even know it, just went in to get new glasses. Was on the operating table two days later. All I
can say, is if you notice anything, go in right away.
Floaters aren't too bad. You get used to 'em pretty quick. But the shadow people are a bee-yatch.
If you get this kind, go to a specialist. I had one in 1997 - the lazy idiot that I went to at first viewed me as a gravy train and had me come in weekly to "monitor" it. After 4 weeks, I asked for a referral to a specialist, walked downstairs, and in 15 minutes he had diagnosed it and I came back the next day for laser spot-welding of the spot that had torn. That is it, no problems since. If I am in strong light and then blink rapidly I can see the triangle of welds.
FOr me, it is like constantly staring at bacterium under a microscope. They are second nature to me now (20+ years), but when I concentrate or look into a light source, It is like looking at a slide of pond water under 50x magnification. I've gone to specialists, and they tell me that there is nothing to correct it.
Floaters move out of the visual field at the same angular veolcity of a scurrying spider about 10 feet away or a mouse at 30 feet.
Here in Dallas, they are offering a new lens implant that not only corrects your far vision, it corrects the deterioration of your up-close reading vision as you age as well. And on top of that the replacement lens will never develop cataracts.
Crystal Lens Offers Cataract Patients New Focus
http://www.wral.com/health/3328197/detail.htmlFAYETTEVILLE, N.C. -- If you had to choose, would you rather see things up close or far away? People with cataracts used to have to make that decision.
The crystal lens is the first implant that works exactly like the human eye. The lens, which is attached to muscles in the eye, instantly adjusts focus so people with it can also see objects that are near and far.With cataract surgery, doctors remove the cloudy lens and replace it with an artificial one. The problem is that the lens had one setting -- either near or far.
Now, people with cataracts and other eye conditions do not have to make that difficult choice. The crystal lens is the first implant that works exactly like the human eye.
The lens instantly adjusts focus so people with it can see objects that are near and far.
"It's introduced the ability to correct the loss of accommodation, or moving the focus," said Dr. Michael Woodcock.
During the 10-minute procedure, Woodcock attaches the lens to the muscles in the eye.
"It will kick in pretty well in about two weeks, and it will continue to improve for about a year," he said.
In clinical trials, most patients no longer needed glasses. Woodcock says 98 percent of those patients could read small print.
The surgery is primarily for people with cataracts. Woodcock also uses it on patients, like Ron Matthews, who want to get rid of their glasses or contacts, but cannot have LASIK.
A brain aneurysm destroyed the muscle around Matthews' eye.
"Anything touching the right side of my head really gets irritated," he said.
Matthews is one of the first people to get the crystal lens. Leona O'Berry had the procedure in March.
"So far I'm amazed at how much I can see," she said. "I have not worn glasses since the day I had the second operation, the second eye done," she said.
As Matthews waits to have the procedure on his second eye, he says he cannot believe how well he sees already, and is excited about what is to come.
"It's phenomenal. You feel like a new person," he said.
The procedure is so new that insurance companies are still figuring out how to cover it.
The crystal lens itself costs $800. Right now, Medicare does not cover it. Many private insurance companies will pay for the procedure, but the patient must pay for the lens.
Face huggers?
During the 10-minute procedure, Woodcock attaches the lens to the muscles in the eye.
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