Thursday, February 19, 2009
Floaters and posterior Vitreous detachment.
What are the floaters?
As the name suggest, floaters are little "cobwebs" or specks that float about in your field of vision. They are small, dark, shadowy shapes that can look like spots, thread-like strands, or squiggly lines. They move as your eyes move and seem to dart away when you try to look at them directly. They do not follow your eye movements precisely, and usually drift when your eyes stop moving.
Most people have floaters .they are usually not noticed until they become numerous or more prominent. Floaters can become apparent when looking at something bright, such as white paper or a blue sky.
What causes floaters?
The vitreous is a transparent gel-like substance that fills about 80 percent of the eye volume (please refer the picture). It helps the eye to maintain its round shape. Due to degenerative processes (old age or inflammation) its contents are lost and it slowly shrinks. This process may lead to development of liquid pockets in between interwoven gel substance .Which ultimately causes the collapse of vitreous gel and leads to detachment from its adhesion sites with the retina. As the vitreous shrinks, it becomes somewhat stringy, and the strands can cast tiny shadows on the retina. These are floaters.
In most cases, floaters are part of the natural aging process however there are other, more serious causes of floaters, including infection, inflammation (uveitis), hemorrhage, retinal tears, and injury to the eye. Over the time the floaters tend to "settle" at the bottom of the eye, becoming less bothersome. They usually settle below the line of sight and do not go away completely.
Who is at risk for floaters?
Floaters are more likely to develop as we get older and are more common in people who are very nearsighted, have diabetes, had trauma to the eye or who have had a cataract operation. There are some congenital disorders which allows vitreous to degenerate fast.
What is a vitreous detachment?
Generally the vitreous gel is a semisolid jelly like substance inside the eye. It is adherent to the retina at multiple places and remains in position due to these tight junctions. The degenerative processes in the vitreous forms lots of liquid pockets inside the gel substance. The sheer forces of movement no longer can hold the whole vitreous together and its starts moving at a different rate than the eye movements. This leads to separation of vitreous from its retinal attachment sites. Once the vitreous is totally detached from retina it becomes free moving body inside the eye and finally sinks inferiorly.
Although a vitreous detachment does not threaten sight, once in a while some of the vitreous fibers pull so hard on the retina that they create a hole or lead to a retinal detachment. Both of these conditions (retinal hole and retinal detachment) are sight-threatening and should be treated immediately.
What are the symptoms of a vitreous detachment?
Usually the symptoms affect one eye and over the years it may involve the other. Bilateral symptoms are not rare as well-
• Floaters - seen as spots, dots, circles, clouds, spidery webs, or various effects. All "float" in front of the eyes and move with the eye.
• Flashes - Visual light without any source, due to the vitreous pulling on the retina
• No symptoms - in some cases PVD is only found on routine eye examination
• Sudden loss of vision –due to hemorrhage or retinal detachment.
How it is diagnosed?
It can be diagnosed by examination, which includes-
• Dilated eye exam to evaluate the vitreous, retina with the help of indirect ophthalmoscopy and diagnostic lenses.
• Eye ultrasonography- when the cornea, lens or vitreous is not clear.
Floaters and Retinal Detachment
The floaters originate due to degenerative process in the vitreous. The posterior vitreous detachment is the sequel of the degenerative process and retinal detachment is the unusual complication of the posterior vitreous detachment. It is important that floaters are common feature for retinal detachment and posterior vitreous detachment.
The only way to diagnose the cause of the problem is by a comprehensive dilated eye examination. If the vitreous detachment has led to a retinal hole or detached retina, early treatment can help prevent loss of vision.
What is the treatment?
For people who have floaters that are simply annoying, no treatment is recommended. Over the time with the collapse of vitreous body all floaters tends to disappear. No doubt it’s a slow process and takes years.
On rare occasions, floaters can be so dense and numerous that they significantly affect vision. In these cases, a Vitrectomy (a surgical procedure that removes floaters from the vitreous) may be needed. This operation carries significant risks to sight because of possible complications. Most eye surgeons are reluctant to recommend this surgery unless the floaters seriously interfere with vision.
What is the prognosis?
Often being a normal part of aging, posterior vitreous detachment does not require specific treatment. So in general this holds a very good prognosis.
However, a sudden increase in floaters, possibly accompanied by light flashes or peripheral (side) vision loss, could indicate a retinal detachment.
Those who experience a sudden increase in floaters, flashes of light in peripheral vision, or a loss of peripheral vision should have an eye care professional examine their eyes as soon as possible.