The retina is supplied by a dense network of very fine blood vessels — the smallest the body has. Persistently raised blood sugar damages precisely these vessels: their walls become leaky, some of them close off, and areas of the retina receive a poorer blood supply. This is diabetic retinopathy.¹
It is one of the most common consequences of diabetes mellitus and affects people with type 1 and type 2 diabetes alike. The difference lies in the timing: with type 1 the start of the condition is usually known; with type 2 diabetes, blood sugar has often been raised for years before the diagnosis — which is why some people already have changes in the retina at the time of diagnosis.
The key message in one sentence. Diabetic retinopathy causes no symptoms at all for a long time — by the time you notice something, a lot has often already happened in the retina. That is why regular eye examinations are not an exaggerated precaution but the real protection for your sight.
Not to be confused with age-related macular degeneration: that is an ageing process at the point of sharpest vision and has nothing to do with sugar metabolism. Both can be present at the same time.
2. Why screening is the real protection
The logic is unfamiliar: with most illnesses you see a doctor because something hurts. Here you go even though nothing hurts — and that is exactly where the benefit lies. Early changes can only be seen by looking at the back of the eye; if they are picked up, the course can be influenced. If you wait for symptoms, the damage — often no longer reversible by then — is considerably greater.²
In Germany, the retinal examination for people with known diabetes is covered by statutory health insurance — it is not something you have to pay for yourself.
When for the first time: With type 2 diabetes, straight after the diagnosis. With type 1 diabetes, the start depends on how long you have had the condition and on your age.
How often after that: Depending on the findings and your risk. If the retina is clear and your metabolic control is good, longer intervals are possible; if there are changes, checks are more frequent. The interval is set by the eye practice together with your diabetes care team.
What is examined: Visual acuity, eye pressure and above all the back of the eye with the pupils dilated, supplemented by OCT and angiography if needed.
What to bring: Your HbA1c and blood pressure readings, your medication plan and the date of your last examination.
You are not fit to drive after your pupils have been dilated. The pupils stay wide for hours, and your vision is blurred and sensitive to glare — arrange for someone to go with you. More on this under Medications and driving.
A common misconception: a sight test at the optician's does not replace this examination — microaneurysms, bleeds and swelling cause no deterioration in vision at first.
3. How the damage develops
The vessel walls start to leak. Tiny bulges (microaneurysms) form, from which fluid, protein and fat escape. If this collects at the point of sharpest vision, macular oedema develops — a swelling that makes reading blurred.
Vessels close off. Other capillaries close completely, and the areas beyond them receive too little oxygen — you cannot feel this.
The body responds the wrong way. The lack of oxygen releases growth signals, above all the messenger substance VEGF. The retina forms new vessels — but unfit ones: thin-walled and disorganised. They grow into the vitreous, tear easily and bleed; strands of scar tissue can pull the retina away. This stage is called proliferative, and it is the dangerous one.
The process runs over years and silently — the retina has no pain fibres.
4. The stages at a glance
The classification determines the check-up interval and the treatment.³
Stage
Visible on the retina
What you notice
Typical approach
Non-proliferative, mild to moderate
Microaneurysms, small bleeds, fatty deposits
Usually nothing
Optimise metabolic control and blood pressure
Non-proliferative, severe
Extensive bleeds, beaded veins, larger areas with a poor blood supply
Mostly nothing
Close monitoring, preventive laser depending on the findings
Proliferative
New, abnormal vessels on the retina or the optic disc, vitreous haemorrhage
A sudden “shower of soot”, shadows, rapid loss of vision — or nothing
Panretinal laser, IVOM if needed; vitrectomy for bleeding or detachment
Macular oedema
Fluid at the point of sharpest vision, possible at any stage
Blurred, distorted reading — the most common cause of worsening vision in diabetes
Anti-VEGF injections, plus focal laser
Table scrolls to the right
Two points matter: macular oedema is the most common cause of poorer vision in diabetes and can appear early on. And a severe non-proliferative stage can progress unnoticed to a proliferative one — that is exactly where the check-up helps most.
5. Symptoms — and why they come too late
There is no early symptom you can rely on. Whatever you notice is already one of the advanced signs:
Blurred reading — typical of macular oedema; see blurred vision.
Fluctuating sharpness of vision when blood sugar swings widely — a temporary swelling of the lens. Not retinopathy, but often mistaken for it.
New black dots, threads or a “shower of soot” — usually bleeding into the vitreous. A shadow or curtain coming in from the side can point to retinal detachment.
Sudden, painless loss of vision — always a warning sign.
The overview under Visual disturbances helps you put things into context. And to say it clearly once more: good eyesight does not rule out retinopathy that needs treatment.
6. Risk factors
Duration of diabetes — the strongest factor. It cannot be changed, but the pace of progression can.
Blood sugar control (HbA1c) — clearly lowers the risk and slows progression. The target is set individually by your diabetes care team.
Blood pressure — underestimated and almost as important as blood sugar. Well-controlled high blood pressure measurably protects the retinal vessels.
Smoking — speeds up practically every complication of diabetes.
Blood lipids and kidney function — raised blood lipids encourage deposits in the retina, and reduced kidney function often goes hand in hand with more pronounced retinopathy.
Pregnancy — a special case: with pre-existing diabetes, retinopathy can worsen rapidly during pregnancy. That is why an examination before a planned pregnancy and close monitoring throughout are standard. Gestational diabetes does not usually carry this risk.
Two numbers, one goal. Anyone with diabetes who thinks about their eyes usually thinks only of blood sugar. In fact, blood sugar and blood pressure count together — and blood pressure is checked at home less often. How to measure both is explained in Measuring blood sugar correctly and Measuring blood pressure correctly.
7. Treatment starts with your metabolism
The most effective treatment does not take place at the eye at all: good, stable metabolic control and well-controlled blood pressure. Laser and injections are repair measures — they often save sight, but they cannot undo what has already happened.³
The HbA1c target depends on age, other conditions and the risk of hypoglycaemia. Depending on the type of diabetes, treatment includes lifestyle measures and medicines such as metformin, modern drug classes or insulin; practical tips are in the guide Diabetes medications in daily life. For blood pressure, ACE inhibitors such as ramipril or sartans are often used, which also protect the kidneys. The choice is made by the treating practice.
Why taking your medicines regularly matters so much here. Blood pressure medicines and diabetes medicines work unobtrusively: you feel neither when they are working nor, straight away, when they are missing — which is why they are forgotten particularly often. In the retina, these gaps add up over the years. A fixed time for taking them is not a convenience here but part of the treatment; the basics are in How to take medications.
Record your readings instead of guessing — the trend tells you more than a single value.
Understand your lab results — HbA1c, blood lipids and kidney values should be read together; help is at hand in Understanding blood values.
Link your appointments — attach the retinal check to an existing diabetes appointment; what sits in the calendar together gets cancelled less often.
Pass on your results — the eye report belongs with your diabetes care, and vice versa.
Blood sugar, blood pressure and eye appointments in one record
brite reminds you to take your medicines and keeps your readings ready for your next consultation.
A connection that surprises many people and rarely comes up unprompted: very rapidly lowering an HbA1c that has been markedly raised for a long time can temporarily worsen existing retinopathy. This has been known since the large diabetes studies and is mentioned in guidelines.³,⁴
Put simply: over the years, the retinal vessels have adapted to a high sugar concentration. If your metabolism is changed drastically within a few weeks, blood flow and fluid balance shift abruptly; existing damage can become more pronounced for a few months. That does not mean high blood sugar would be better — in the long term, good control is clearly the better path. The consequence is a different one:
Lower it in a controlled way: With very high starting values, step by step over months, not at top speed.
See the ophthalmologist first: Before treatment is stepped up significantly — for example when starting insulin — a retinal check makes sense.
Monitor more closely: If retinopathy is already pronounced, check-ups are scheduled more frequently during the changeover phase.
Do not steer it yourself: The pace of lowering belongs in the hands of the treating practice.
One sentence for your next appointment. “My HbA1c is going to be lowered considerably — should my retina be checked first?” Asking costs nothing and makes sense here. Help with wording is under Prepare for a doctor's appointment.
9. Laser, injections, vitrectomy
If the retina shows changes that need treatment, three procedures are available, often in combination. The decision is made by the eye practice together with you.⁵
LaserLaser coagulation
Panretinal laser coagulation
In proliferative retinopathy, areas of the outer retina with a poor blood supply are sealed with the laser; the growth signal falls and the abnormal vessels regress. The price: the procedure sacrifices parts of the outer field of vision and can worsen vision at dusk — in order to save central vision.
Focal laser
Targeted treatment of individual leaking spots, today mostly in addition to injections.
InjectionIVOM: medicines injected into the eye
Anti-VEGF injections
The standard for macular oedema involving the centre of vision: the active substance blocks the signal that makes the vessels leak, and the swelling goes down. Initially several monthly injections, after that depending on the findings.
Cortisone implants
An option if anti-VEGF is not enough or frequent appointments are not feasible. Points to note: a possible rise in eye pressure and faster clouding of the lens.
SurgeryVitrectomy
Removal of the vitreous
Considered for a vitreous haemorrhage that does not clear, for strands of scar tissue and for a retinal detachment caused by traction. The clouded vitreous is removed and replaced, often combined with laser treatment.
Here too, keeping your appointments helps determine the outcome: macular oedema that returns between two appointments spaced too far apart costs sharpness of vision that cannot always be regained.
10. Warning signs
Do not wait and see with these signs. A sudden painless loss of vision, a new dark shadow or “curtain” coming in from the side, many new black dots or a swarm of fine specks — often described as a “shower of soot” — and new flashes of light should be checked by an ophthalmologist promptly, and outside surgery hours at an emergency department. The “shower of soot” is the typical picture of a vitreous haemorrhage from abnormal new vessels; a curtain can point to retinal detachment. Both are treatable — but time matters. For making sense of other changes in vision, see Visual disturbances.
Another reason to bring your next appointment forward: blurred or distorted reading that lasts for days while your blood sugar is stable. This can be new macular oedema — treatable, and the earlier the better.
11. Other complications
The retina is a window onto the small blood vessels of the whole body — what can be seen there does not concern the eye alone.
Kidneys: Retinopathy and chronic kidney disease often occur together — an abnormal eye finding is a good reason to have your kidney values checked.
Nerves:Polyneuropathy, with tingling and numbness in the feet and legs, follows the same pattern.
Heart and blood vessels: Pronounced retinopathy goes along with a higher risk of cardiovascular events.
Other eye conditions: With diabetes, a cataract often develops earlier, and certain forms of glaucoma are more common. These are also assessed at the check-up.
The practical benefit: the retinal check tells you not only about your eyes but also gives a snapshot of the state of your blood vessels as a whole.
A year goes by quickly — don't forget the retinal check
Set the reminder once and keep your readings, medicines and reports alongside it.
Yes, especially then. Diabetic retinopathy causes no symptoms for years, and good vision does not rule out changes that need treatment. Only looking at the back of the eye reveals early damage. Anyone who waits for symptoms often comes too late to prevent part of the damage.
The interval depends on the findings and your risk and is set individually. With no retinal changes and good metabolic control, longer intervals are possible; otherwise the checks are more frequent. With type 2 diabetes, the first examination takes place straight after the diagnosis. It is covered by statutory health insurance.
Very early changes can partly regress if metabolic control improves considerably. Advanced damage, especially areas of the retina that have died off, usually does not regress. Treatment and good control aim to halt progression and preserve your sight.
If an HbA1c that has been markedly raised for a long time is lowered very rapidly, existing retinopathy can temporarily get worse; the retinal vessels react to the abrupt change. That is why very high values are lowered in a controlled way over months and the retina is checked more closely during this phase. In the long term, good control remains the better path.
Here, fluid escapes from leaky vessels into the point of sharpest vision and makes it swell; reading becomes blurred or distorted. It is the most common cause of worsening vision in diabetes and can occur at any stage. It is usually treated with anti-VEGF injections, with focal laser as an addition.
Many people use this to describe a sudden swarm of dark dots or specks in their field of vision. In diabetes it is typically bleeding into the vitreous from abnormal new vessels. It needs to be checked promptly by an ophthalmologist, and outside surgery hours at an emergency department. If a dark curtain appears as well, retinal detachment is suspected.
gesund.bund.de, the national health portal of the German Federal Ministry of Health: Diabetic retinopathy. Accessed 2026 — German source. gesund.bund.de
Gesundheitsinformation.de, German Institute for Quality and Efficiency in Health Care (IQWiG): Retinal disease in diabetes. Accessed 2026 — German source. gesundheitsinformation.de
German S3 guideline on the specific diagnosis and treatment of retinal complications in diabetes (led by the DOG and BVA, AWMF reg. no. 045-024) — German source. awmf.org
Medical disclaimer: This article is for general information and does not replace medical advice, diagnosis or treatment. Good eyesight does not rule out retinal changes that need treatment — no self-test can replace an examination by an ophthalmologist. If you experience a sudden painless loss of vision, a dark curtain, flashes of light or a sudden swarm of dark dots (a “shower of soot”), see an eye practice or an emergency department promptly. Never change the dose of diabetes or blood pressure medicines on your own; the choice of medicine and its dose is always set individually by the treating practice. Last updated: September 2026.
