What does posterior vitreous detachment mean?
To understand a PVD, it helps to first understand what the vitreous humour is. The vitreous is the clear, gel-like substance that fills the large cavity inside your eye, between the lens at the front and the retina at the back. It gives the eyeball its shape, and in a young, healthy eye it is firmly attached to the retina all the way around, with particularly strong connections at the optic nerve, the macula, and along the major blood vessels.
A posterior vitreous detachment occurs when this gel peels away from the surface of the retina. The word "posterior" simply means the back of the eye. As the gel detaches, it collapses towards the centre of the vitreous cavity and floats there, separated from the retina by a thin layer of fluid that has seeped in through the attachment points.
A useful way to picture this is to imagine a glass bowl filled with jelly, turned upside down. Left to its own devices, the jelly begins to pull slowly away from the sides of the bowl, peeling free bit by bit until it would eventually fall entirely. That peeling action is a reasonable illustration of what happens during a PVD. The retina is the bowl, the vitreous is the jelly, and what you are watching is the slow, progressive separation of one from the other. The difference, fortunately, is that unlike jelly falling from a bowl, the vitreous has nowhere to go. It simply collapses inward and floats in the centre of the eye.
How a posterior vitreous detachment produces floaters
The moment this happens, many people notice something new in their vision: a floater. This is not a coincidence. What you are seeing is the collapsed gel itself, or fragments of it, casting a shadow on your retina. In many cases the most prominent floater is a ring-shaped opacity called a Weiss ring, which forms at the point where the gel was attached to the optic nerve.
A PVD is not a disease. It is a normal, age-related change in the structure of the eye. It happens to most people eventually. The concern is not the detachment itself, but whether the process of detachment has caused any damage on the way.
Why does a PVD happen?
The vitreous gel changes throughout your life. In childhood and early adulthood it is a firm, structured gel, similar in consistency to raw egg white. Over time, particularly from the age of forty onwards, the gel begins to liquefy in patches. Water separates out from the collagen framework within the vitreous, forming fluid-filled pockets called lacunae. As this process progresses, the gel loses its structural integrity, and eventually there is enough fluid pooled behind the posterior cortex of the vitreous to allow it to peel away from the retina.
Think of it like wallpaper that has been on a damp wall for many years. The adhesive weakens gradually, until one day a whole section lifts away from the surface all at once.
Most people will experience a PVD in both eyes before they reach their seventies or eighties. However, it can happen earlier, and certain factors accelerate the process:
Factors that increase the likelihood of an earlier PVD
Short-sightedness, known clinically as myopia, is the most significant risk factor. A myopic eye is longer than average, and the vitreous gel within it undergoes the same liquefaction process in a larger space, which tends to bring the detachment on sooner. People with significant myopia often experience PVDs in their forties or even thirties.
Previous eye surgery, particularly cataract surgery, is also associated with earlier PVD. The surgical process and subsequent changes to the lens can disrupt the vitreous and hasten detachment. Eye injury, uveitis (inflammation inside the eye), and certain inherited connective tissue disorders such as Marfan syndrome can have a similar effect. Interestingly, PVDs are also somewhat more common following a PVD in the fellow eye, as if the biological clock for this process runs in both eyes at roughly the same pace.
What does a PVD feel like?
A PVD does not hurt. There is no sensation in the eye during the process. The first and most common sign is the sudden appearance of new floaters, often described as a large dark ring, a cobweb, a cloud of small dots, or a curved line that drifts slowly across your vision when you move your eyes. These are different in character from the small, thread-like floaters that many people have had quietly for years. They are new, they are prominent, and they tend to appear suddenly.
The second common symptom is flashes of light. These appear as brief, arc-shaped streaks of white or silver light, usually in the peripheral vision, and most noticeable in dim light or when you move your eyes quickly. They are caused by the vitreous gel pulling on the retina as it detaches. This traction stimulates the retinal cells in the same way that light does, producing the sensation of a flash. Once the vitreous has fully separated and there is no longer any mechanical pull on the retina, the flashes should stop. If they persist, or if they become more frequent, that warrants urgent attention.
Floaters from a PVD often appear suddenly and are more striking than the small, translucent floaters many people have lived with for years. The sudden change is what typically prompts people to seek assessment.
Can a PVD cause a retinal tear?
This is the central clinical concern with any acute PVD, and it is the reason that an eye examination is recommended whenever you develop the symptoms. As the vitreous gel peels away from the retina, it exerts traction, a pulling force, on the areas where the attachment was strongest. In most cases the gel detaches cleanly. In a minority of cases, roughly one in ten at the time of initial presentation, the traction is sufficient to tear the retina as it pulls away.
A retinal tear is not the same as a retinal detachment, but an untreated retinal tear is one of the main causes of retinal detachment. Once a tear is present, fluid from the vitreous cavity can pass through it and lift the retina away from the underlying tissue, much as water can seep beneath a loose tile and lift it from the floor. If that detachment reaches the central retina, the visual consequences can be severe and permanent.
The reassuring part of this picture is that retinal tears can be treated quickly and effectively when they are found early. Laser treatment takes only a few minutes and seals the tear by creating a small area of controlled scarring around it, preventing fluid from passing through. Once a tear has been sealed in this way, the risk of detachment is removed.
- A sudden large shower of new floaters, particularly many small dark dots
- Persistent flashes of light that are increasing in frequency
- A shadow, curtain, or veil at the edge of your vision
- A sudden reduction in the clarity of your vision
If you notice any of these changes, do not wait. Seek a same-day eye examination. These symptoms do not guarantee that something serious has happened, but they do mean that a prompt dilated examination of the retina is needed that day.
What happens after a PVD?
If the initial examination shows a healthy retina with no tears, the prognosis is excellent. The floaters you have developed will not disappear overnight, but most people find that they become considerably less noticeable over the weeks and months that follow. The brain is remarkably good at adapting to persistent visual phenomena and learning to ignore them. The vitreous gel also continues to settle deeper into the vitreous cavity with time, moving the floaters further from the central visual axis.
It is worth understanding that the risk of a retinal tear is not entirely confined to the first few days after a PVD. The vitreous can continue to shift and exert traction for several weeks after the initial event, and a small number of retinal tears occur during this period rather than at the time of detachment. For this reason, if you develop new floaters or flashes in the weeks following your initial assessment, particularly if they are different in character or more numerous than before, it is sensible to return for a further examination rather than assuming the process is complete.
Most ophthalmology departments will ask you to return for a review examination at four to six weeks after an acute PVD, even if the initial examination was normal. This is good clinical practice, and it is worth attending.
What a PVD means in practice
- Most PVDs are uncomplicated and do not cause lasting damage
- All new PVDs should have a dilated retinal examination promptly
- Roughly one in ten has a retinal tear at presentation, which can be treated easily if found early
- Floaters often become less noticeable over weeks to months
- A follow-up examination at four to six weeks is standard practice
- Return promptly if symptoms worsen or change before your follow-up
When to seek same-day help
The following symptoms require urgent assessment on the same day, not a routine appointment in a week's time. They may indicate a retinal tear or the early stages of a retinal detachment, and the window for effective treatment narrows the longer these go unexamined.
- A sudden dramatic increase in the number of floaters
- Many small dark specks appearing all at once, sometimes described as a pepper shower
- Persistent or worsening flashes of light
- A shadow, curtain, or grey veil appearing at the edge of your vision
- Any sudden change in the clarity or quality of your central vision
Contact your local eye casualty department, A&E, or call 111 for urgent ophthalmology advice. Do not wait until the next morning if symptoms appear in the evening.
Common questions about PVD
Is a posterior vitreous detachment dangerous?
The great majority of posterior vitreous detachments are uncomplicated and do not cause lasting damage. However, roughly one in ten people with an acute PVD has a retinal tear at the time of presentation, which is why a dilated eye examination is recommended whenever you develop symptoms of a new PVD. The condition itself is a normal part of ageing. The risk lies in the small possibility of an associated tear.
Will the floaters from a PVD go away?
The floaters often become less noticeable over weeks and months, partly because the brain adapts to them and partly because the vitreous gel continues to settle away from the centre of your vision. They rarely disappear entirely, but for most people they become much less intrusive with time. A very small number of people are significantly affected by persistent floaters long term, and in those cases treatment options exist, though these carry their own risks and are not routinely recommended.
Can a PVD happen in both eyes?
Yes. A PVD will eventually occur in both eyes in most people, though not usually at the same time. Once you have had a PVD in one eye, it is common for the other eye to follow within months to a few years. When it does, the same principle applies: new symptoms should prompt prompt assessment, because the risk of retinal tear is the same for the second eye as it was for the first.
What should I do if I think I am having a PVD?
You should have your eyes examined promptly, ideally within a day or two of noticing new floaters or flashes. The examination needs to include a dilated view of the retina. Most optometry practices can perform this assessment, as can hospital eye departments. If you notice a sudden large increase in floaters, persistent flashes, or any shadow or curtain across your vision, treat this as urgent and seek same-day assessment.
Does everyone with a PVD need treatment?
No. A PVD itself does not require treatment. The examination is to rule out a retinal tear, which does require treatment. If no tear is found, the management is reassurance, observation, and a follow-up examination at four to six weeks. Only if a tear is identified is treatment, typically laser retinopexy, needed.
Concerned about new floaters or flashes in your vision?
When to worry about floaters