Posterior Vitreous Detachment and Floaters

Introduction

A posterior vitreous detachment (PVD) occurs when the collagen fibers which make up the vitreous cavity 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 fibers, hemorrhage, 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.

Pathogenesis

A simple explanation is that age-related changes in the vitreous cause the vitreous gel to collapse and pull forward. In actuality, liquification or syneresis of central vitreous occurs. Then a small hole develops in posterior cortical vitreous. The liquified vitreous passes through the hole into the space between the vitreous and the retina. This causes the collagen fibers to come forward and condense. The fibers will always stay attached just behind the iris to an area called the vitreous base.

Initially the gel fills the entire vitreous cavity.

Normally the gel pulls forward with minimal problems. A piece of tissue from the optic nerve called a Weiss ring may be visible as an arc-chaped floater.

In some patients, the gel will not break away "cleanly" and may cause a retinal tear. The most common tears are called horseshoe tears because of their clinical appearance. If the gel continues to pull on the flap of the tear, the fluid in the vitreous can go through the tear and cause the retina to detach. If there is a tear only, it can often be treated with laser or freezing (cryotherapy) alone. If the retina detaches, a surgical procedure is required.

Clinical Findings

Fifteen (15) percent of all symptomatic patients will have a tear. The presence of a hemorrhage is predictive of a greater chance of having a retinal tear. Only 2-4% of patients without vitreous hemorrhage have a tear, while 70% of patients with vitreous hemorrhage have a tear.

If there is an area of vitreoretinal adhesion, the foward-pulling force can create a retinal tear.

With normal eye movement, fluid can then pass through the retinal tear and cause a retinal detachment.

If a vitreous hemorrhage obscures view, a B-scan ultrasound examination will be performed to determine if there is an underlying retinal detachment.

There are certain characteristics that make a retinal tear or detachment more likely. Those who are nearsighted (myopic), those who have had previous intraocular surgery (cataract, YAG laser), and those who have a family history of a retinal tear or detachment all have a slightly higher risk compared to patients without these factors. In addition, retinal conditions such as lattice degeneration (retinal thinning), severe ocular trauma, or a history of a previous detachment in their other eye also increase this risk.

Follow-Up

The exact follow-up interval for patients with a PVD is somewhat controversial. Based on our experience, a repeat evaluation in approximately 2 months allows for detection of most asymptomatic retinal tears. By then, most patients' symptoms have improved dramatically.

The most important thing is to monitor your vision daily. Cover each eye and test yourself to see if there are any changes in your central or peripheral vision. Call us for any of the following:

• Multiple new floaters
• Multiple flashes
• Changes in peripheral vision

Floaters

A floater is any type of opacity in the vitreous gel which generally moves with eye or head movement. Floaters may cause a wide range of visual problems and symptoms. Patients may describe these as spots, clouds, webs, or clumps. In many patients, they are only a nuisance, but in some patients, they may significantly interfere with activities of daily living such as reading, driving, or watching TV. These patients may benefit from surgical intervention.

Despite some advertising claims, no drops or eye vitamins will help the floaters go away more than observation alone. Most patients do well without any intervention, as the brain can begin to “ignore” them. However, in the patients who remain symptomatic, surgery can be very effective in eliminating this problem.

Laser for Floaters

A YAG laser may be used to break down floaters in select cases. Patients with significant opacities located in the anterior vitreous cavity (behind the lens or lens implant) may benefit from this procedure. Often however, the floaters are more posterior, and this becomes a highly controversial subject. It may be difficult to identify the floaters from which the patient's complaints arise. In practice, this has not been widely adapted but two physicians on the East coast perform this treatment frequently for floaters. The overall risk seems fairly low, and this may be appropriate to attempt before vitrectomy surgery.

Surgery for Floaters

If a patient's floaters do not improve after a couple of months of observation, and they interfere with activities of daily living, we do believe it is appropriate to consider a vitrectomy. This is where the vitreous gel is removed and replaced with clear saline solution. Performing a vitrectomy for floaters is also controversial and some retinal surgeons will not perform this procedure. There are risks associated with any procedure, but if a patient has enough visual disability, the benefits of the procedure generally outweigh the risks. We have found that in carefully selected patients, vitrectomy eliminates the patient's symptoms and is a highly successful procedure.