What is a Posterior Vitreous Detachment?
The vitreous is a clear substance within the eye, which has a gel-like consistency. If you think of the inside of your eye as being hollow, the vitreous may be thought of as occupying approximately two thirds of this hollow space. This vitreous gel is composed of 99% water, and the other 1% consists of special substances known as collagen and hyaluronic acid, which endow the vitreous with its gel-like consistency.
The vitreous has many functions, which include:
- To help maintain the shape of the eye
- To act as a shock absorber
- To allow transmission of light from the external environment to the retina (located immediately behind the vitreous)
- To help keep the retina in contact with the back wall of the eye
Normally, the back surface of the vitreous is in direct contact with the retina and the blood vessels which supply the retina. However, in most eyes the vitreous becomes more liquid and at some point will pull away or separate from the retina and collapse into the central hollow part of the eye. This even constitutes a posterior vitreous separation or detachment (PVD) and is a normal aging process.
What are the symptoms of posterior vitreous detachment?
- Floaters. A person typically sees anywhere from a few to hundreds of dark spots or objects "floating" in the field of vision. These floaters may represent bleeding inside the eye, or torn retinal tissue, but they usually represent particles that have been in the vitreous all along. With normal aging, the vitreous becomes more liquid and the particles can float and be seen. When they were fixed in space in the more solid gel, the brain did not notice them. Floaters have also been described as "spots and dots," "a cloud of smoke," or a "swarm of bees."
- Lightning flashes. Lightning flashes are generated by the vitreous tugging on the retina during eye movement. When a posterior vitreous detachment occurs, there may initially be residual areas where the vitreous remains attached to the retina, causing these light flashes. Patients have described these flashes as "a sparkle or twinkle," "a disco light," or "fireflies."
- Decreased vision. Decreased vision is not usually present, although vision can decrease secondary to bleeding inside the eye or retinal detachment.
If retinal detachment develops early on, central vision may be normal but some patients begin to note a "curtain, veil, or fog" that may progressively obscure the peripheral vision, followed by loss of central vision.
Will I have a posterior vitreous detachment (PVD)?
Most people will have a posterior vitreous detachment by 70 years of age and many will develop this change sooner. It is important to note that the eyes are healthy without associated eye disease. If you have PVD in one eye, it is common to develop it in the other eye over the next year or two.
Following is a list of events that may lead to a posterior vitreous detachment:
- A history of cataract surgery
- Inflammation inside the eye
- Injury to the eye (such as blunt trauma, accident, or falls)
- Bleeding inside the eye
Each event is a risk factor for developing a PVD.
Are posterior vitreous detachments dangerous?
The majority of people who develop a posterior vitreous detachment are not in danger of further eye complications. The only residual symptom may be the persistence of a few floaters.
In 7% to 15% of those who have a posterior vitreous detachment associated with floaters, lightning flashes, or decreased vision, there may be an associated retinal tear. A retinal tear can lead to a retinal detachment. Unfortunately, the symptoms of a vitreous detachment without an associated retinal tear are the same as those with a tear. The presence of a tear will only be recognized by an ophthalmologist during a dilated eye examination.
When is it important to be examined?
If a retinal tear does occur during a posterior vitreous detachment, it usually happens at the same time as one begins to experience symptoms of the PVD. Therefore, it is important to be examined shortly after these symptoms begin. Additionally, in a small percentage of patients, the tear may occur many weeks after the onset and subsidence of symptoms. For this reason, your physician may request that you return for a repeat examination usually in four to six weeks. If the PVD process is complete and there is no retinal tear, the recommended follow up schedule can revert to the schedule generally recommended for someone your age and with other eye problems you may have. Usually, an exam is advised again in a year. Be sure to ask to be examined sooner if you have new symptoms or a change in your vision.
How is posterior vitreous detachment treated?
If the posterior vitreous detachment has occurred without associated retinal tears, therapy is not required or indicated. The vitreous will continue to age and liquefy and floaters will usually become less and less noticeable. With time, most people's symptoms will completely disappear.
If a retinal tear has occurred, treating the retinal tear with laser or cryopexy (a freezing treatment to close the tear) is usually recommended. Surgery will be indicated if the tear has progressed to a retinal detachment.
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