Retina & Vitreous
Retina and vitreous — what lies behind flashes and a shower of floaters
The retina rarely announces itself with pain. It announces itself with flashes of light, with sudden new black dots, with a shadow that moves into the field of vision from the side. These signs are harmless — or the beginning of a retinal detachment. From the outside that cannot be told apart; with the pupil dilated it can.
What the retina and the vitreous do in the eye
The retina is the innermost layer of the eye: a wafer-thin layer of nerve tissue that converts light into signals and passes them on to the brain along the optic nerve. At its centre lies the macula, the point for sharp vision — reading, faces, road signs. Injured or deprived of its supply, nerve tissue barely regenerates. That is why, with findings in the retina, it is often not the treatment method that decides the outcome but the timing.
The vitreous body (Corpus vitreum) fills the space in front of it. It consists largely of water and a fine scaffold of collagen fibres, and in a young eye it is evenly gel-like. Over the years it liquefies and shrinks. In doing so it separates from the retina — in the great majority of cases without consequence. Sometimes, though, it pulls so hard at one point that the retina tears.
That is exactly why the retina and the vitreous are assessed together: most acute retinal problems begin at this interface between the two. Where this area sits within our specialty is shown in the overview of ophthalmology.
These warning signs belong in a consultation today
- Flashes of light (photopsia) — usually at the edge of the field of vision, often clearer in the dark
- A shower of floaters — many new black dots, flecks or a 'swarm' that appears suddenly
- A shadow or curtain, moving into the field of vision from the outer edge
- Suddenly distorted vision — straight lines appear wavy, letters jump
- Rapid, painless deterioration of vision in one eye
None of these signs hurts. That is exactly where the danger lies: symptoms without pain get put off. But with a retinal detachment that is beginning, days count, not weeks. Which four warning signs appear in which order, and when the call must not wait until the next day, is described on the page of its own about it: Recognising retinal detachment — the four warning signs and the route to an emergency assessment.
If one of these signs is new for you, call us: +41 44 500 69 00 (Mon–Fri 08:00–12:00 / 13:00–17:30). Outside these hours please contact the ophthalmic emergency service or go directly to the emergency department of an eye clinic. Do not wait until the next regular appointment.
What can be behind it
Retinal detachment (Amotio retinae) — the emergency among retinal findings
In a retinal detachment the retina lifts off the layer beneath it and is cut off from its supply. The order is typical: first flashes, then a shower of floaters, then a shadow that grows larger. A detached retina does not reattach on its own — it has to be dealt with surgically, and quickly. If the macula is not yet involved, the window of time is especially valuable. If you suspect this, go for an ophthalmic examination today, not tomorrow.
Posterior vitreous detachment
The most common cause of sudden new 'floaters' and flashes — and as a rule age-related and harmless. The vitreous separates from the retina, which you perceive as moving shadows. It is harmless, though, only once the retina has been checked all round in mydriasis (with the pupil dilated): in a small proportion of cases the retina tears as this happens. The examination is the real service here, not the diagnosis.
Macular pucker (epiretinal gliosis)
A fine membrane grows on the centre of the retina and draws it into folds. Vision does not get darker, it gets distorted: lines ripple, images appear warped (metamorphopsia). Many findings stay stable over years and are only monitored. If the distortion gets in the way day to day, the membrane can be removed in the course of an operation inside the eye — a procedure that most reliably improves the distorted vision and rarely brings visual acuity back in full. Distorted vision can also come from other changes at the centre of the retina — one of them is age-related macular degeneration (AMD).
Macular hole (macular foramen)
Here the retina itself tears at the centre — usually through traction from the vitreous. People affected describe a grey patch exactly where they are looking, and distorted letters. A macular hole seldom resolves on its own; it is dealt with surgically, and the timing influences the outcome.
Diabetic retinopathy
Blood sugar raised over many years damages the finest vessels of the retina. For a long time that does not hurt and causes no symptoms — and it is nonetheless one of the most common causes of loss of vision during working life. That is why people with diabetes belong in regular ophthalmic monitoring, even when they see well. How often depends on the findings and on the progression; we settle that together. Which stages there are, which warning signs do not wait until the next appointment and how it is treated is set out on its own page on why the retina stays silent for so long in diabetes and what the annual check finds. For a check-up like this, when there are no acute symptoms, you can book an appointment for a retinal check-up online — if you have new flashes, a shower of floaters or a shadow, call us instead.
How we examine the retina and the vitreous
- Examination of the back of the eye in mydriasis. Without a dilated pupil the periphery of the retina — where tears and holes form — cannot be assessed reliably. Allow time for it and do not come by car: the drops go on working for several hours and make you sensitive to light.
- OCT (optical coherence tomography). A cross-sectional image of the retina at microscopic resolution, without contact and without radiation. It shows fluid, membranes, holes and swelling of the macula — and makes the progression comparable over years.
- Fundus autofluorescence (FAF). Makes the retina's metabolism visible. Andrea von Rückmann co-developed this method and published it as first author in 1995; today it sits alongside OCT among the standard diagnostics of the macula.
- Fluorescein angiography (FA). An image of the retinal vessels using a dye. It shows leaking areas and areas with a poor blood supply — above all in diabetic retinopathy and vascular occlusions. We use it selectively, when the answer changes the treatment, not as a routine.
Retinal laser treatment: when lasering really helps
If the examination shows a retinal tear or a hole without the retina having already detached, laser coagulation (retinopexy) can make sense. The laser places fine burns around the tear, and over the following days these form a scar. This scar bonds the retina to the layer beneath it — the tear itself remains, but it can no longer spread. The procedure is done as an outpatient at the slit lamp, with anaesthetic eye drops and a contact lens, and as a rule takes a few minutes.
Two things we say openly here:
A laser does not improve vision. It prevents deterioration. Anyone expecting to see more sharply after the treatment will be disappointed — even though the treatment has done exactly what it is meant to do.
A retina that has already detached cannot be lasered. Then an operation is necessary. Anyone who is given a laser appointment in two weeks in this situation has been wrongly advised.
And one more clarification, because the search terms are the same: 'Laser eye surgery' in everyday speech usually means correcting a refractive error — short-sightedness, astigmatism. That is a procedure on the cornea, right at the front of the eye, and has nothing to do with retinal laser treatment apart from the word 'laser'. Two different structures, two different aims, two different indications. We do not offer laser eye surgery to correct a glasses prescription. If that is what you are looking for, you are on the wrong page here — and if you are seeing flashes or shadows, on the right one.
Treatment routes at a glance — and where we refer you
| Finding | Usual approach |
|---|---|
| Retinal tear without detachment | Laser coagulation, then follow-ups |
| Retinal detachment | Surgery inside the eye, urgent |
| Macular pucker, macular hole | Observation or surgery, depending on symptoms |
| Diabetic macular oedema | Drug injection into the eye, laser in selected cases |
| Proliferative diabetic retinopathy | Panretinal laser coagulation, in some cases with injections in addition |
Operations inside the eye — the vitrectomy, in which the vitreous is removed and the retina is dealt with from inside — we do not carry out ourselves. If your finding calls for one, we tell you straight away and arrange the referral to a retinal surgery centre, so that you do not have to see to it yourself. The diagnostics beforehand and the follow-ups afterwards we take on close to where you live, in Zurich, Wetzikon or Meilen.
Diagnosis and treatment of diseases of the retina and the vitreous are medical services. Where there is a medical indication the cost is covered by basic health insurance (OKP); the deductible and co-payment apply as at any doctor's appointment.
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Medically reviewed by PD Dr. med. Andrea von Rückmann · Last reviewed
Frequently asked questions
- A shower of floaters is how people describe many small black dots or flecks that appear suddenly in the field of vision and drift along with the gaze. Behind them are usually blood cells or pigment in the vitreous — material that does not belong there. The trigger can be a harmless vitreous detachment, but it can also be a retinal tear with a small haemorrhage. Because the two cannot be told apart from the outside, a new shower of floaters belongs in an ophthalmic examination within 24 hours.
- 'Floaters' known for a long time and unchanged are as a rule harmless and need no treatment. What matters is the change: markedly more dots than usual, new flashes of light, a shadow at the edge. Then a check with the pupil dilated is indicated. In short: what has been there a long time is rarely the problem; the sudden increase is.
- By the combination and by the timing: flashes of light, suddenly many new black dots and then a dark shadow that moves into the field of vision from the outer edge and grows over hours to days. Pain is almost always absent. A red eye is almost always absent. It is exactly this absence of anything noticeable that leads people to wait too long. With this pattern the rule is: have it assessed today.
- Yes. Diabetic retinopathy begins without symptoms, and by the time vision declines a fair amount has already happened. The retina is also the only place in the body where vessels can be looked at directly — so the check says something about the state of the vessels as a whole as well. The interval between checks depends on the findings, how long you have had diabetes and how your blood sugar is controlled.
- For a complete assessment of the retina: yes. The drops need around 20 to 30 minutes to take effect and wear off over several hours. During that time your near vision is blurred and you are sensitive to light. So plan the appointment without a car and bring sunglasses with you. Anyone who knows this experiences it as an inconvenience — anyone who does not, as a surprise.
- Where there is a medical indication — that is, with symptoms, with a noticeable finding or with an underlying condition such as diabetes — 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 and without an indication, for a purely preventive check, we clear that with you beforehand, so that you find no surprise on the bill.
Flashes, a shower of floaters, a shadow: call today, not tomorrow.
On the phone, describe to us what you are seeing and since when. We will tell you straight away whether it can wait until tomorrow — or whether we should examine you today.
+41 44 500 69 00 — Mon–Fri 08:00–12:00 / 13:00–17:30. Or book an appointment online.