WHAT IS A POSTERIOR VITREOUS DETACHMENT

If you new to the floater game and doing your research on the topic of vitreous eye floaters, you will undoubtedly come across the term “Posterior Vitreous Detachment” or PVD. May your own eye doctor mentioned it as part of their evaluation of your new-onset shadowy figures moving across your vision. A PVD is a very common, usually age related phenomenon, an event, a shift of fluids that occurs in the eye. If I were to examine a randomly chosen group of 60-year old people, I would find evidence of a PVD in about 25%. That number would go up to about 60% of 80 year old people. Remember, this is a randomly chosen group of people, not necessarily having any symptoms of floaters.

Rule/Observation #1: “Floaters are common and usually related to age”
Rule/Observation #2: “The presence of a PVD does not necessarily mean that eye floaters are present and symptomatic”

There is also a lot of confusion to the term “Posterior vitreous detachment” because of the similarity to “Retina detachment”. They are often anatomically or causally related, but they are also quite different in terms of risk and threat to the eye. Unless the eye has a penetrating injury or some other retinal abnormality, most of the spontaneous retinal holes or tears that may lead to a retinal detachment are caused by a PVD.

The American Academy of Ophthalmology defines a PVD:
Posterior vitreous detachment (PVD): A separation of the posterior vitreous cortex from the internal surface of the retina. This usually occurs as an acute event after substantial age-related liquefaction in the vitreous gel; the separation usually extends rapidly to the posterior margin of the vitreous base in all quadrants. Adhesions between the vitreous cortex and retina or retinal blood vessels may cause retinal breaks and/or vessel rupture. Vitreous hemorrhage and/or localized intraretinal hemorrhage may accompany this event. Posterior vitreous detachment is diagnosed by slit-lamp biomicroscopy, which will usually show a prominent plane defining the posterior vitreous face. The presence of a glial annulus in the vitreous cavity (Weiss ring) is strong evidence of PVD.”

It is the asymptomatic age-related liquefaction of the viscous vitreous ‘gel’ that initiates the process. In a younger eye, the vitreous is a ‘visco-elastic’ fluid/gel that is not unlike the consistency of uncooked egg whites. The vitreous is 99% water and 1% collagen proteins that give it some structure, and also makes this fluid a bit ‘sticky’. With time, the distribution of the collagen changes and some may clump up leaving regions of ‘pooled fluid’. The effect is more swirling, liquid movement of the vitreous fluid. If there is enough pooled fluid, it may find its way through, or underneath the surrounding ‘bag’, the vitreous cortex, that surrounds the vitreous and normally lies on top of the retina.

Normal eye without floaters
fig 1. Normal eye without floaters
Very early separation of the vitreous from the retina.
fig 2. Very early separation of the vitreous from the retina. You start to see the beginnings of the Weiss ring coming off the optic nerve head.
The vitreous has completely separated, There is both a Weiss ring and some separate cloudy floater (syneresis) formation.
fig 3.The vitreous has completely separated, There is both a Weiss ring and some separate cloudy floater (syneresis) formation.
The vitreous body has continued to move forward where it is now stably in position.
fig 4. The vitreous body has continued to move forward where it is now stably in position.

If the fluid finds it way underneath the vitreous cortex, it can dissect, or separate the vitreous away from the retina. Most of the time this occurs, there are no symptoms, or just minor and temporary symptoms seen as peripheral flashes of lights. The flashes of lights occur when the is an incomplete separation of the vitreous from the retina and it is still attached to parts of the retina. The swirling of the fluid, and the consequent ‘pulling and tugging’ on the retina is physical traction on the rods and cones of the retina which may or may not occur, but is responsible for the peripheral flashes of light best seen in dim light situations. As the vitreous body pulls further away from the retina and separates completely,there is no longer any attachment to pull and tug, no more traction and so the flashes should disappear.

Rule / Observation #3: At the onset of a vitreous detachment, and especially if flashes are present, you are at your highest risk of spontaneous retinal hole, tear, or detachment.

If the vitreous is separating and you do not have any retina problems, then congratulations you have avoided the vision threatening risks of the separation of the vitreous. If you have significantly bothersome eye floaters as a results of your PVD, wait a few weeks to allow things to stabilize. If some of the floaters are small and start out near the retina, they MAY become less bothersome if they move further away from the retina. Once the vitreous separates completely, the situation should be pretty stable. What you have after a few weeks is pretty much what you are stuck with. Whether it is 1 month, or 1 year, your floaters will not likely improve, although they may get worse. Patients often tell me that their local eye care provider has told them that the floater(s) will get better, drop out of the way, or their brain will learn to ignore them. Although it is possible for some of the smaller floaters, my patients come to me weeks to decades after the onset of their floaters and they have not gotten better on their own. My patients often also admit not just to the quality of vision issues, but also the quality of life issues associated with the floaters: Depression, anxiety, avoiding activities they used to enjoy.

So here is the good news: Eye floaters associated with a posterior vitreous detachment, in those over the age of 45-50, are very likely to be candidates for safe and successful treatment with the YAG laser in the hands of an experienced specialist (read THIS and THIS). Ultimately, though, it does take an in-person evaluation to prognosticate your candidacy for treatment. -Dr. Johnson

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