Posterior Vitreous Detachment
A posterior vitreous detachment (PVD) occurs when the collagen fibres which make up the vitreous (jelly of the eye) condense, causing the gel to “pull forward.” Patients typically complain of seeing central floaters and/or flashes of light, usually in their peripheral vision. This is a normal age-related phenomenon, but in some patients, it can be associated with a retinal tear or detachment.
The flashes are due to the physical stimulus of vitreoretinal traction. With normal eye movements, traction on the retina stimulates the neurons of retina to fire. This signals the brain that it “sees” light. The symptoms of flashes are most prominent in dark conditions, and generally go away with time. A few reproducible flashes, especially with head movement, are not particularly worrisome, and also tend to lessen with time.
The floaters are due to a combination of aggregated or clumped collagen fibres, haemorrhage, and/or glial cells from around the optic nerve. The symptoms due to floaters generally diminish over time, sometimes months. Because the floaters are tissue, they do not go away (unless due to blood), but you learn to gradually ignore them.
What causes Posterior Vitreous Detachment?
As a person gets older, the gel-like material in the vitreous begins to liquefy in the centre. Eventually the vitreous will collapse in on itself, pulling the vitreous free from its attachments on the retina or at the optic nerve. Posterior vitreous detachments occur in less than 10 percent of people under the age of 50 but they occur in more than 60 percent of persons who are 70 years old or older.
Trauma to the eye can also cause a posterior vitreous detachment. A blow to the eye causes traction on the vitreous and can pull the vitreous away from the retina. Trauma can be a factor in posterior detachments occurring in people younger than 40 years old.
Because the eyes of nearsighted or myopic people are longer than the average eye, these people are at a higher risk of developing a posterior vitreous detachment. Statistical evidence has shown that posterior vitreous detachments are associated with nearsightedness.
Infection or Inflammation
Infection in the rear portion of the eye can cause inflammation. This inflammation can cause the vitreous to liquefy as well; this leads to the gel in the vitreous collapsing and the vitreous pulling away from the retina of the eye. Conditions like uveitis–which is an inflammation of the vitreous–can cause a posterior vitreous detachment as well.
People who have had cataract surgery are at higher risk of developing a posterior vitreous development. Patients who have had a specific type of laser surgery called a YAG laser after cataract surgeries are also at risk for posterior vitreous detachments.
What are the symptoms and diagnosis of Posterior Vitreous Detachment
PVD can cause symptoms such as floaters, little flashes of light, or a cobweb effect across your vision. Some people get all three symptoms and others may only get one or two. Some people get a lot of each of these symptoms and others hardly any. Importantly, these same symptoms can be an indication of a more serious problem, such as a retinal tear, which needs urgent attention.
You will not be able to tell the difference between floaters and flashes caused by PVD or retinal detachment. The only way you can tell is to have your eyes examined by an ophthalmologist. If you suddenly experience any of the following symptoms, make sure you have your eyes examined as soon as possible – preferably on the same day or within 24 hours:
- a sudden appearance of floaters or an increase in their size and number
- flashes of light and/or a change/increase in the flashing lights you experience
- blurring of vision
- a dark ‘curtain’ moving up, down or across your vision, as this may mean that the retina has already partially detached.
It is important to remember that in most cases these symptoms are caused by vitreous detachment and this rarely causes any long term problems with your vision. However, because there is a small risk that these symptoms may be a sign of a retinal tear or detachment it is always best to have your eyes examined.
How is Posterior Vitreous Detachment treated?
At the moment there is no medical treatment for PVD. There is no evidence to show that eye exercises, diet changes or vitamins can help a PVD. Because PVD floaters, in most cases, clear up on their own, the possible benefits of surgery do not outweigh the risks involved.
Retinal tears and PVD
As noted earlier, when the vitreous detaches it may tear a hole in the peripheral retina which may be asymptomatic. Use the analogy of prestick on tissue paper. If you peel the prestick off, it will either pull loose from the tissue paper causing no damage to it, or it could tear a piece of the tissue paper with it. The same process happens to the retina when the vitreous pulls loose.
If your Ophthalmologist notices that a piece of retina has been torn but the retina is still attached, then that tear can be “welded” closed with laser. If, however the tear has resulted in a retinal detachement, surgery to reattach the retina is likely indicated.