Is a posterior vitreous detachment dangerous?

If it runs an uncomplicated course, no. It is then a normal ageing process of the eye and as a rule does the retina no harm. What is dangerous is not the detachment itself but the rarer case in which the vitreous tears the retina as it separates — and at the start the two cause exactly the same symptoms. Less often the vitreous stays caught at the centre of the retina and goes on pulling there; a macular pucker or a macular hole can develop from that. That is exactly why every newly appeared detachment needs examining once with the pupil dilated. If the retina is unremarkable, the question is answered: the dots you are seeing are then a nuisance, but harmless.

Do floaters go away again?

They do not dissolve; they usually become markedly less noticeable over time. Two things happen: the opacities sink in the eye and drift out of the line of sight, and the brain learns to compute their shadows away — the same habituation by which you also stop seeing your own nose. How long that takes differs from person to person, and in some of those affected an opacity remains a nuisance. Nobody can responsibly give you a figure for it.

With flashes of light, do I have to see an ophthalmologist straight away?

Yes — newly appeared flashes of light need an ophthalmic examination the same day, as do a new shower of floaters and a dark shadow or curtain moving into the field of vision or growing larger. Do not wait to see whether it improves overnight. Outside consulting hours the ophthalmic emergency service applies. A sudden, complete loss of vision in one eye — particularly with headache, pain on chewing or difficulty with speech or signs of paralysis — does not belong in the consultation but in an emergency department immediately: call the ambulance (144). Floaters known for a long time and unchanged, without flashes, are a different case: those you can raise at your next regular appointment.

What are the black spots I see in my eye?

They are condensations in the vitreous, the gel-like contents of the eyeball. They do not lie on the retina but cast a shadow onto it — which is why the spots travel with your gaze and drift on when you hold the eye still. They are at their most obvious against bright, even surfaces: a white wall, the sky, a screen. Newly appeared, they need examining once; if they have been unchanged for a long time, they are as a rule harmless.

Can floaters be lasered away or operated on?

Operated on yes, in rare cases: a vitrectomy removes the vitreous together with its opacities — the procedure does not, however, promise a completely 'clean' picture, because vitreous remains at the base of the retina. It is an elective procedure inside the eye with real risks — among them cataract, retinal tear, retinal detachment, infection and a rise in pressure — and that is why it only comes up at all with severe, persistent impairment. Laser treatment of vitreous opacities (YAG vitreolysis) is disputed in its effectiveness and not established. We do not carry out operations inside the eye ourselves: we examine, we advise and, where the indication supports it, we arrange the referral.

Does vitreous detachment happen in the second eye too?

As a rule yes, usually with time in between — the process affects both eyes, only rarely at the same time. When the time comes, the same rule applies as the first time: new flashes, a new shower of floaters or a shadow need assessing, even if you know the pattern by now. So at every check-up we examine both eyes, including the one with no symptoms.

Does health insurance cover the examination?

With symptoms — new flashes, a new shower of floaters, suddenly far more dots than before — the assessment is medically indicated, and the cost is covered by basic health insurance. The deductible and co-payment apply as at any doctor's appointment. If you come without symptoms for a purely preventive check, we clear that with you beforehand, so that you find no surprise on the bill. A procedure carried out solely because the opacities are a nuisance is a different case: it is an elective procedure, and what your insurer says about it is for you to settle beforehand through a cost approval.

Retina & Vitreous

Flashes and black dots: posterior vitreous detachment — usually harmless

Suddenly dark dots, threads or cobwebs are floating through your field of vision, and something flickers brightly at the edge: behind it is almost always a posterior vitreous detachment — a normal ageing process of the eye, not a disease and not an emergency. Even so, someone has to look at the retina once with the pupil dilated. Because a retinal tear causes the very same symptoms, and that is the only way to recognise it.

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What a posterior vitreous detachment is — and why it is normal

The vitreous fills the space between the lens and the retina. It consists largely of water, along with a fine scaffold of collagen fibres, and in a young eye it is evenly gel-like. Over the years this gel liquefies and the scaffold contracts. At some point the vitreous separates from the retina it had been lying against until then. That is precisely the posterior vitreous detachment. In medical reports it often appears only as the abbreviation HGA, and in conversation usually the short form 'vitreous detachment' — each of them means the same thing.

It is not a disease but a process the eye goes through in the course of a lifetime. Most often it happens in the second half of life; in short-sighted eyes earlier, because the eyeball is built longer and the vitreous changes correspondingly earlier. Nothing you have done or failed to do sets it off: screen work, reading in poor light, stress or exertion do not bring on a vitreous detachment.

That is why the list of what is not needed after an unremarkable examination is so long: no eye drops, no ban on sport or screens, no change of diet, no food supplements, and as a rule no series of check-up appointments. What is needed first is exactly one thing — that someone looks once, with the pupil dilated, right out to the edge of the retina. Until then, take it easy: no sport, no heavy lifting, no rubbing the eye. Why that one examination is the whole point is set out further down.

Where this process sits among the other findings at the back of the eye — from macular pucker to diabetic retinopathy — is shown by the overview of the retina and the vitreous.

Mouches volantes: what is floating in your field of vision

'Floaters', cobwebs, fluff, rings, threads — or simply black spots in the eye: there are as many descriptions of the same phenomenon as there are people who have it. The French technical term for them is Mouches volantes, the German one 'Glaskörpertrübungen'. They are not the vitreous detachment itself, but what you see of it.

In physical terms this is what happens: as it liquefies, the collagen fibres of the vitreous clump into fine strands and flecks. These do not lie on the retina but float in front of it and cast a shadow onto it. That is why the dots move with your gaze and drift on when you hold the eye still — you cannot fix your eyes on them, they slip away. As it detaches, a ring-shaped remnant often comes away from the optic nerve head as well: anyone who suddenly sees a ring or an 'O' is usually seeing exactly that.

Why they are more noticeable in bright light

A shadow needs a bright, even surface in order to become visible. That is exactly why floaters are at their clearest against a white wall, against snow, against the sky and against a bright screen, and almost gone in a patterned living room. The same goes for the narrow pupil in sunshine: it sharpens the shadow they cast. Sunglasses reduce that effect — one of the few 'tricks' that in our experience do something. Nothing is treated by it; the opacity remains, it is just less noticeable.

What does not help against floaters

For eye drops, food supplements and eye exercises there is no proven benefit in vitreous opacities — we sell you nothing for it, and we also advise against preparations marketed on the internet with exactly this indication. What actually helps is unspectacular: knowing what you are seeing, and that — provided the retina has been examined and is unremarkable — it does no harm. Because anyone who looks for the dots finds them reliably; anyone who stops looking for them notices them less over time. How quickly that happens differs from person to person.

What matters is the distinction this page is meant to carry: What has been there a long time is rarely the problem; the sudden increase is. Floaters known for years and unchanged need no treatment and no appointment. What is new needs looking at once.

When it is not a harmless vitreous detachment

In most places the vitreous separates from the retina without anything happening. In individual spots it adheres more firmly — and there its traction can tear the retina. A sudden swarm of fine black dots has an established name: A shower of floaters. Such a swarm often comes from a tear like that: blood cells and pigment get into the vitreous, and those you can see. But it also occurs with an uncomplicated detachment — from the outside the two cannot be told apart, and that is why the same deadline applies to both. If a tear goes undetected, liquefied vitreous can run under the retina and lift it off.

An emergency that comes before even that: A sudden, complete loss of vision in one eye — particularly together with headache, pain on chewing, difficulty with language or speech, or signs of paralysis — does not belong in our consultation but in an emergency department, immediately: call the ambulance (144). Behind it can be a vascular occlusion or a vascular inflammation, where minutes and hours count.

Every one of the following situations needs assessing the same day:

a dark shadow or curtain, moving into the field of vision or growing larger
new flashes of light, particularly if they last for hours or increase
suddenly a great many more black dots than before, or a swarm of them you have never seen before
a pair of rapid, painless deterioration of vision in one eye
the same signs after eye surgery, a blow to the eye or an accident — even weeks later

This list is word for word the same as on the page that describes the serious case, and that is deliberate: these are exactly the signs by which a retinal detachment announces itself — warning signs, the time window and what to do in an emergency with a retinal detachment. Anyone who knows them need not fear a vitreous detachment. Anyone who does not know them puts the call off, because nothing hurts — and that is the real reason a readily treatable finding becomes lasting damage.

You should be somewhat more alert if one of these constellations applies to you: pronounced Myopia, an eye after cataract surgery, a blunt injury or wound to the eye, known thin patches of retina, or retinal detachments in the family. A risk factor is not a diagnosis — it is a reason to know the signs above by heart.

What is not part of a vitreous detachment and therefore does not go back to it either: pain, a red eye, discharge, eyelids stuck together. A painful red eye is likewise a case for the same day, just a different one. And the other way round: a single dot, known for a long time and unchanged, is not an emergency and never was.

Why a thorough examination with the pupil dilated is necessary

'Posterior vitreous detachment' is not a diagnosis you can make from the description. It is the answer that remains once a retinal tear has been ruled out — and that ruling-out is the real service. From the outside the harmless detachment and the dangerous tear look identical, because both produce the same flashes and the same swarm. With the pupil dilated they can be told apart.

Behind that is a window of time that closes. A tear without a detached retina can be walled off at the slit lamp with the laser as an outpatient: the laser places fine burns around the tear, and over the following days these form a scar that bonds the retina to the layer beneath it. As a rule that takes a few minutes. Once the retina has detached, this route is closed and an operation is needed — depending on the finding, inside the eye (vitrectomy) or from outside with a sutured-on buckle. Which procedure is used when, we describe on the retinal detachment page. Between these two situations there are sometimes only days — and that window is exactly why we do not put you off to the next free appointment when symptoms are new.

What happens at this appointment:

Dilation of the pupil (mydriasis). Without it the periphery of the retina — where tears form — cannot be assessed reliably. The drops need around 20 to 30 minutes to take effect and wear off over several hours. That is the honest price of this examination, and we would rather tell you before than after.
Funduscopy of the entire back of the eye. Assessment far out to the edge, if needed with indentation of the wall of the eye so that even the outermost parts can be seen.
OCT, where the question calls for it. A contact-free cross-sectional image of the retina — above all where the centre of the retina could be involved or the vitreous is still pulling there.
Ultrasound, when blood blocks the view. A haemorrhage in the vitreous makes the retina invisible to a lens and light. Ultrasound shows through cloudy media as well whether it is in place.
The second eye. It is examined too, even when it has no symptoms.

An exception to the rule 'one look is enough'. If the examination shows blood or pigment in the vitreous, or if the periphery of the retina could not be seen in full, we see you again — even when nothing has changed and the retina was in place at first look. A tear can then be hiding behind the opacity, and it shows itself only once the opacity clears. When that check takes place we tell you with the finding; it is then not a preventive appointment but part of the same assessment.

For the question of a retinal tear this examination needs no blood test, no imaging of the head and no referral — the case is different with a sudden loss of vision accompanied by headache or pain on chewing, which belongs in an emergency department by ambulance (144) and needs exactly those investigations there. And what this examination cannot do: rule out a retinal tear without the pupil having been dilated. An eye test, a look at visual acuity or a pressure measurement say nothing about it — anyone who has had flashes and a shower of floaters and been examined without dilation has not had the examination that decides it. What else belongs to a complete ophthalmic examination we describe separately.

If the retina is unremarkable we tell you exactly that — and whether a follow-up check makes sense at all is decided by the finding and not by the calendar. If your symptoms are new, call us; if the finding has been unchanged for a long time, you can book an appointment for a retinal check online.

Progression and habituation — what happens over the coming months

The flashes of light usually stop once the vitreous has fully detached: they arise from traction on the retinal tissue, and where there is no more traction there are no more flashes. Until then they can keep occurring over days to weeks, typically at the edge of the field of vision and clearer in the dark. New flashes, or flashes that are markedly increasing, remain a reason to call, though — even if the retina was in order two weeks ago.

Not every flashing comes from the eye. A shimmering zigzag arc that travels slowly through the field of vision over some 20 to 30 minutes, appears the same in both eyes and carries on with the eyes closed — with or without a headache afterwards — speaks for a migraine aura and not for traction on the retina. A retinal finding, by contrast, produces brief flashes in one eye, usually at the edge of the field of vision and without that travelling. If you are experiencing this for the first time or are unsure, have it assessed: the pattern is typical, but the distinction is worth having confirmed once.

The opacities take a different route. They do not dissolve. They sink lower in the eye, drift out of the line of sight and, above all: the brain stops reporting them. This habituation is not a consolation but the actual course of things — the same feat by which you also stop seeing your own nose and the rim of your glasses. How long it takes differs greatly from person to person, and in some of those affected an opacity remains a permanent nuisance. Any figure for it would be invented.

What supports this process is modest, but real: choose your light so that the contrast is not at its maximum — screen brightness down, sunglasses in bright conditions; and stop checking on the dots. Anyone who counts them daily against the white wall is training exactly the attention that is meant to disappear.

One sign deserves a mention of its own here, because it is not part of that habituation: distorted vision — straight lines ripple, letters jump, a grey patch sits exactly where you are looking. That does not come from the vitreous but from the centre of the retina, from something such as a macular pucker, a fine membrane on the retina, a macular hole or age-related macular degeneration (AMD). Changes like these need examining, even when they develop slowly.

Vitrectomy for floaters — rare, and never in passing

For a small proportion of those affected the opacities remain a real impairment even after months: when reading, at the screen, when driving. For that situation there is a procedure. Vitrectomy: through fine ports the vitreous, together with its opacities, is removed and replaced with a clear fluid. The opacities that cast the shadows are taken out with it. What the procedure does not promise, though, is a completely 'clean' picture: vitreous remains at the base of the retina, and individual opacities can stay or become noticeable again later.

The price belongs in the calculation just as much. It is an operation inside a healthy eye, and it brings the risks of such an operation with it: in an eye with its own natural lens, what frequently develops afterwards is a Cataract, which then itself has to be operated on. On top of that come a retinal tear or a retinal detachment, a rise in intraocular pressure and — rarely, but seriously — an infection inside the eye. The benefit is a gain in comfort; the risk is a risk to sight. That calculation only works out with severe, persistent impairment, and only where it has first been shown cleanly that the opacities are the sole cause of the symptoms.

That is why this procedure is an elective procedure and not a medical necessity — a difference that counts for your insurer too; see the section on costs further down.

YAG vitreolysis: 'lasering away' the opacities

A laser can break up larger opacities in the vitreous so that they are less noticeable — so-called YAG vitreolysis. Its effectiveness is disputed and the method is not established: it does not work on every kind of opacity, success is hard to predict, and side effects in the eye have been described. If you ask about it, we tell you what the findings in your eye allow, instead of giving you an appointment.

What we do — and what we refer on

We do not carry out operations inside the eye ourselves. What we do is the part before and after: examine, place the finding in context and tell you whether your impairment supports this procedure at all. Where it does come into question in an individual case, we arrange the referral to a retinal surgery centre; the follow-ups afterwards we take on close to where you live, in Zurich, Wetzikon or Meilen. And when we advise waiting, we tell you why as well — and what you would notice if the situation changed.

Costs & health insurance

What does the insurer pay for — and what not?

Assessing a posterior vitreous detachment is a medical service: anyone seeing new flashes, a new shower of floaters or suddenly far more dots has an indication. The case is different where a procedure is on the table solely because existing opacities are a nuisance — that is an elective procedure, and it changes the billing.

Service	Coverage	What this means for you
Assessment for new flashes, a shower of floaters or mouches volantes	Basic insurance (OKP)	Examination with the pupil dilated, funduscopy and — where the question calls for it — OCT or ultrasound are medically indicated where there are symptoms. The deductible and co-payment apply as at any doctor's appointment.
Laser coagulation of a retinal tear	Basic health insurance where indicated	If the examination finds a tear, the treatment is medically indicated. It is billed against the same deductible as the assessment it follows from.
Follow-up check after a posterior vitreous detachment	Basic health insurance where indicated	A check-up that we expressly schedule after the finding is a medical service. If you come without symptoms and without an indication for a purely preventive check, we clear that with you beforehand.
Vitrectomy solely because vitreous opacities are a nuisance	Subject to conditions	An elective procedure with no compelling medical indication. Whether basic health insurance covers anything, and to what extent, is decided by your insurer case by case and as a rule only after prior cost approval. Settle that before a date for an operation is fixed.
Food supplements, eye exercises or tinted lenses for floaters	Not covered	For vitreous opacities there is neither insurance cover for this nor any proven benefit. Sunglasses can soften the shadows they cast in bright light — but they treat nothing, and we sell you nothing for it.

You bear the deductible and co-payment yourself, as at any doctor's appointment. If you would like to know beforehand what to expect, ask us — on the phone on +41 44 500 69 00 or through the contact form. With new warning signs we assess first and sort out the administration afterwards.

Related conditions

Retinal detachment Retina & vitreous Eye examinations

Medically reviewed by PD Dr. med. Andrea von Rückmann

Your ophthalmologistPD Dr. med. Andrea von RückmannView profile

Frequently asked questions

: If it runs an uncomplicated course, no. It is then a normal ageing process of the eye and as a rule does the retina no harm. What is dangerous is not the detachment itself but the rarer case in which the vitreous tears the retina as it separates — and at the start the two cause exactly the same symptoms. Less often the vitreous stays caught at the centre of the retina and goes on pulling there; a macular pucker or a macular hole can develop from that. That is exactly why every newly appeared detachment needs examining once with the pupil dilated. If the retina is unremarkable, the question is answered: the dots you are seeing are then a nuisance, but harmless.
: They do not dissolve; they usually become markedly less noticeable over time. Two things happen: the opacities sink in the eye and drift out of the line of sight, and the brain learns to compute their shadows away — the same habituation by which you also stop seeing your own nose. How long that takes differs from person to person, and in some of those affected an opacity remains a nuisance. Nobody can responsibly give you a figure for it.
: Yes — newly appeared flashes of light need an ophthalmic examination the same day, as do a new shower of floaters and a dark shadow or curtain moving into the field of vision or growing larger. Do not wait to see whether it improves overnight. Outside consulting hours the ophthalmic emergency service applies. A sudden, complete loss of vision in one eye — particularly with headache, pain on chewing or difficulty with speech or signs of paralysis — does not belong in the consultation but in an emergency department immediately: call the ambulance (144). Floaters known for a long time and unchanged, without flashes, are a different case: those you can raise at your next regular appointment.
: They are condensations in the vitreous, the gel-like contents of the eyeball. They do not lie on the retina but cast a shadow onto it — which is why the spots travel with your gaze and drift on when you hold the eye still. They are at their most obvious against bright, even surfaces: a white wall, the sky, a screen. Newly appeared, they need examining once; if they have been unchanged for a long time, they are as a rule harmless.
: Operated on yes, in rare cases: a vitrectomy removes the vitreous together with its opacities — the procedure does not, however, promise a completely 'clean' picture, because vitreous remains at the base of the retina. It is an elective procedure inside the eye with real risks — among them cataract, retinal tear, retinal detachment, infection and a rise in pressure — and that is why it only comes up at all with severe, persistent impairment. Laser treatment of vitreous opacities (YAG vitreolysis) is disputed in its effectiveness and not established. We do not carry out operations inside the eye ourselves: we examine, we advise and, where the indication supports it, we arrange the referral.
: As a rule yes, usually with time in between — the process affects both eyes, only rarely at the same time. When the time comes, the same rule applies as the first time: new flashes, a new shower of floaters or a shadow need assessing, even if you know the pattern by now. So at every check-up we examine both eyes, including the one with no symptoms.
: With symptoms — new flashes, a new shower of floaters, suddenly far more dots than before — the assessment is medically indicated, and the cost is covered by basic health insurance. The deductible and co-payment apply as at any doctor's appointment. If you come without symptoms for a purely preventive check, we clear that with you beforehand, so that you find no surprise on the bill. A procedure carried out solely because the opacities are a nuisance is a different case: it is an elective procedure, and what your insurer says about it is for you to settle beforehand through a cost approval.

Newly appeared? One proper look, and then you have peace of mind.

Tell us on the phone what you are seeing and since when. New flashes, a new shower of floaters or a shadow in the field of vision need examining the same day; during consulting hours we see you for that the same day, outside them the ophthalmic emergency service applies. If the retina is unremarkable we tell you so — and you do not have to come back, as long as nothing changes and the finding does not expressly call for a follow-up check.

Call now — arrange an assessment

+41 44 500 69 00 — Mon–Fri 08:00–12:00 / 13:00–17:30. Outside consulting hours the ophthalmic emergency service applies. Or book an appointment online.