Vitreous floaters

Published on June 30, 2016   22 min
I'm Jerry Sebag, professor of clinical optomology at the Doheny Eye Institute and founding director of the VMR Institute for Vitreous Macula Retina in Southern California. We'll now consider the visual impact of a posterior vitreous detachment that is not anomalous in part 2.
The last topic that I'm going to be discussing is a consequence of posterior vitreous detachment that has previously been considered an innocuous event but is currently being reconsidered in terms of a disease. Recall that posterior vitreous detachment requires liquefaction of the gel, vitreous, as well as dehiscence at the vitreo-retinal interface in order for the poster vitreous detachment to be innocuous. And by innocuous, what we're referring to is that there are none of the anomalous changes that we've just considered that result in retinal tears and detachments, vitreo-macular traction syndrome, macular holes, and macular pucker. In the absence of all of those manifestations of anomalous PVD, it has previously been considered that a PVD is innocuous. However many patients experience floaters. And in some of those individuals, the floaters are serious.
The origin of the floaters is light scattering by the dense collagen matrix of the posterior vitreous cortex. Recall that I mentioned earlier, the reason we can visualize the peripheral vitreous by dark field slit microscopy is because there's a very dense aggregation or a high density of collagen fibrils in the peripheral vitreous. And that's shown here on scanning electron microscopy. It is a bit exaggerated by the dehydration that the specimens have to undergo in order for the preparation for scanning EM, but I think it's very useful for demonstrative purposes, to appreciate what that looks like. And here you can see the appearance of the posterior vitreous cortex in preset lens biomicroscopy in an eye. This is the optic disk here. The retinal vessels are branching from the optic disk, and this is the location and the typical appearance of posterior vitreous detachment.
Another source of the floaters phenomenon is the Weiss ring, and this is the area of firm vitreo-retinal adhesion to the optic disk. Very often, when the vitreous separates from the optic disk, you can see the fibrous material from around the optic disk that has separated with the posterior vitreous cortex, resulting in shadows that are cast upon the retina. And patients will very often describe and even draw the appearance of the shadows in this configuration. Here, you can see ultrasonography of an individual with a posterior vitreous detachment and a Weiss ring. This is the posterior vitreous cortex here, and this is the appearance of the Weiss ring by ultrasound. Here is another individual. The optic nerve is here. Its insertion into the globe is here, and this is the appearance of the Weiss ring in an individual with a posterior vitreous detachment.
There are also aggregates within the vitreous that can interfere with the transmission of light to the retina, creating light scattering and inducing floaters. But the critical question is whether floaters are a nuisance or a disease.
Recent studies have shown that the negative impact of floaters are perceived by patients as equal to the severity of age-related macular degeneration and greater than glaucoma and diabetic retinopathy. Patients who were surveyed felt that floaters were equal in severity to angina, stroke, colon cancer, and asymptomatic AIDS. These individuals were willing to take an 11% risk of death and a 7% risk of blindess to undergo procedures to rid them of floaters and, indeed, were willing to exchange 1 out of 10 years of remaining life to be rid of floaters. Subsequent studies have validated these findings in 107 floater patients, and a recent smartphone survey reported that 76% of smartphone users reported having floaters. And a third of these claimed to be impaired. Now there may be some bias based upon the use of smartphones by a certain segment of the human population, but nevertheless these fly in the face of what we previously felt was an innocuous condition that should be dealt with. And the patients were, for years, advised to cope with these floaters.
And it puzzled me as to why patients would consider floaters a disease, and yet doctors consider them just a nuisance. And I submit for your consideration that the main reason that doctors have been able to accept floaters as a disease is because of the absence of clinical indices of structural and functional abnormalities in patients who have floaters. These people are typically 20-20, and in the absence of retinal tears and detachments, areas of hemorrhage, and the like, these people are counseled to not be concerned and simply deal with the floaters. And the absence of typical techniques for the measure of the severity of the floaters has hampered our ability to accept floaters as a disease.