Posterior vitreous detachment, usually shortened to PVD, is the separation of the vitreous gel from the surface of the retina. Despite how the name sounds, it is not a retinal detachment and it is not a disease — it is an expected age-related change that most people experience at some point.

It matters clinically for one reason: the symptoms it produces are identical to the symptoms of a retinal tear, and only an examination can tell which has occurred.

The cavity behind the lens is filled with vitreous, a clear gel that in youth is firmly attached to the retinal surface and holds a stable, uniform structure.

With age the gel gradually liquefies. Pockets of fluid form, collagen fibers clump together, and the gel loses volume. Eventually it collapses forward and peels away from the retina. That separation is the PVD.

It is most common after the age of 50 and becomes progressively more likely with each decade. It tends to occur earlier in people who are significantly nearsighted, after cataract surgery, and following eye trauma or inflammation.

Two separate mechanisms produce the two symptoms.

Floaters are shadows. The clumped collagen fibers and the ring of tissue that detaches from around the optic nerve float freely in the gel and cast shadows on the retina. Patients often describe a prominent new floater — a ring, a large cobweb, or a dense strand — that moves as the eye moves and drifts to a stop when the eye is still.

Flashes are traction. Where the vitreous is still attached, its pull tugs mechanically on the retina. The retina responds to any stimulation by sending a visual signal, so the brain interprets that tug as light — typically a brief arc at the edge of vision, more noticeable in the dark.

Flashes usually diminish over weeks as the separation completes and traction is released.

In most people the vitreous separates cleanly and nothing further occurs. In a minority, the pull at a point of firm attachment tears the retina, and a tear can allow fluid to pass beneath it and progress to a retinal detachment.

There is no way to distinguish an uncomplicated PVD from a PVD with a retinal tear based on symptoms. Both cause flashes and floaters, and the severity of the symptoms does not reliably indicate which has happened.

The examination is therefore a dilated inspection of the entire retina including the far periphery, often with gentle indentation of the eye to bring the outermost edge into view. Because a tear can appear days or weeks after the initial symptoms, a repeat examination some weeks later is commonly recommended even when the first is normal.

If you have been told you have a posterior vitreous detachment and no tear was found, return promptly if you notice:

• A new shower of floaters, distinct from those already present
• Flashes that return or increase after settling
• A shadow, curtain or dark area in any part of your vision
• Any drop in vision

A shadow or curtain in particular should be treated as urgent — see detached and torn retina.

An uncomplicated PVD requires no treatment. The floaters remain, though they usually become less intrusive over months as they settle out of the direct line of sight and as the visual system learns to ignore them. Flashes typically resolve.

Occasionally the vitreous remains partly attached at the macula and pulls on it, which can lead to distortion and, in some cases, a macular hole or epiretinal membrane. This is uncommon and is detected on OCT.

The second eye typically undergoes the same process within a few years. Knowing what the symptoms mean makes it easier to recognize — but the same rule applies: new flashes or floaters in the second eye need their own examination.

New floaters or flashes need an examination

A posterior vitreous detachment is usually harmless, but it cannot be distinguished from a retinal tear without a dilated exam. Call (602) 613-5473 to be seen at our Scottsdale office.