A posterior vitreous detachment is a condition of the eye in which the
vitreous membrane separates from the retina. It refers to the separation of
the posterior hyaloid membrane from the retina anywhere posterior to the
vitreous base Broadly speaking, the condition is
common for older adults and over 75% of those over the age of 65 develop it.
Although less common among people in their 40s or 50s, the condition is not
rare for those individuals. Some research has found that the condition is
more common among women. Causes and risk factors
The vitreous humor is a gel which fills the eye behind the lens. Between it and
the retina is the vitreous membrane. Over time the vitreous humor changes,
shrinking and developing pockets of liquefaction, similar to the way a
gelatin dessert shrinks, or detaches, from the edge of a pan over time. At
some stage the vitreous membrane may peel away from the retina. This is
usually a sudden event, but may also occur slowly over months.
Age and refractive error play a role in determining the onset of PVD in a
healthy person. PVD is rare in emmetropic people under the age of 40
years, and increases with age to 86% in the 90s. Several studies have found a
broad range of incidence of PVD, from 20% of autopsy cases to 57% in a more
elderly population of patients. People with myopia greater than 6
diopters are at higher risk of PVD at all ages. Posterior vitreous detachment
does not directly threaten vision. Even so, it is of increasing interest because
the interaction between the vitreous body and the retina might play a
decisive role in the development of major pathologic vitreoretinal
conditions, such as epiretinal membrane. PVD may also occur in cases of cataract
surgery, within weeks or months of the surgery.
The vitreous membrane is more firmly attached to the retina anteriorly, at a
structure called the vitreous base. The membrane does not normally detach from
the vitreous base, although it can be detached with extreme trauma. However,
the vitreous base may have an irregular posterior edge. When the edge is
irregular, the forces of the vitreous membrane peeling off the retina can
become concentrated at small posterior extensions of the vitreous base.
Similarly, in some people with retinal lesions such as lattice retinal
degeneration or chorio-retinal scars, the vitreous membrane may be abnormally
adherent to the retina. If enough traction occurs the retina may tear at
these points. If there are only small point tears, these can allow glial cells
to enter the vitreous humor and proliferate to create a thin epiretinal
membrane that distorts vision. In more severe cases, vitreous fluid may seep
under the tear, separating the retina from the back of the eye, creating a
retinal detachment. Trauma can be any form from a blunt force trauma to the
face such as a boxer's punch or even in some cases has been known to be from
extremely vigorous blowing of the nose. Symptoms
When this occurs there is a characteristic pattern of symptoms:
Flashes of light A sudden dramatic increase in the number
of floaters A ring of floaters or hairs just to the
temporal side of the central vision As a posterior vitreous detachment
proceeds, adherent vitreous membrane may pull on the retina. While there are no
pain fibers in the retina, vitreous traction may stimulate the retina, with
resultant flashes that can look like a perfect circle.
If a retinal vessel is torn, the leakage of blood into the vitreous cavity is
often perceived as a "shower" of floaters. Retinal vessels may tear in
association with a retinal tear, or occasionally without the retina being
torn. Complications
The risk of retinal detachment is greatest in the first 6 weeks following
a vitreous detachment, but can occur over 3 months after the event.
The risk of retinal tears and detachment associated with vitreous detachment is
higher in patients with myopic retinal degeneration, lattice degeneration, and
a familial or personal history of previous retinal tears/detachment.
Treatment Therapy is not required or indicated in
posterior vitreous detachment, unless there are associated retinal tears,
which need to be repaired. In absence of retinal tears, the usual progress is
that the vitreous humor will continue to age and liquefy and floaters will
usually become less and less noticeable, and eventually most symptoms will
completely disappear. Prompt examination of patients experiencing vitreous humor
floaters combined with expeditious treatment of any retinal tears has been
suggested as the most effective means of preventing certain types of retinal
detachments. See also
Vitreous membrane Central serous retinopathy
List of eye diseases and disorders Epiretinal membrane
Vitrectomy References