The importance of early diagnosis
Diabetic retinopathy is silent in its early stages. The patient continues to see well while the damage progresses, and only an ophthalmologist can detect the first changes during fundus examination. For this reason, everyone with diabetes must have regular eye check-ups, even without symptoms.
Much of the damage is irreversible
Once retinal capillaries become blocked or neovascularisation develops, established damage does not recover. Early diagnosis makes it possible to act before permanent damage occurs — it is today the most effective tool for preventing vision loss caused by diabetes.
- Type 1 diabetes
- Guidelines recommend the first check within 5 years of diagnosis of diabetes, then at the interval advised by the ophthalmologist.
- Type 2 diabetes
- Guidelines recommend an eye examination at the time of diagnosis of diabetes, then at the interval advised by the ophthalmologist.
- Pregnant women
- Check in the first trimester, repeated if the ophthalmologist requests it.
- What is needed
- Eye examination with pupil dilation, OCT (for macular oedema), fluorescein angiography if indicated.
The 6 main tests
Diagnosis of diabetic retinopathy is based on a complete assessment that combines six instrumental tests. It always starts with dilated fundus examination; the others are added according to clinical signs.
- 01
Dilated fundus examination
Essential basic testIt is the key test for diagnosing diabetic retinopathy. It requires pupil dilation with eye drops (effect lasting 4-6 hours) and is painless. It allows the ophthalmologist to examine the retina directly, looking for microaneurysms, haemorrhages, exudates, neovessels and signs of oedema.
It is combined with fundus photography (retinography) to document the state of the retina over time, and with indirect ophthalmoscopy when a wider view of the peripheral retina is needed.
What the ophthalmologist looks for
- 02
OCT — Optical Coherence Tomography
Macular imagingOCT works like a 'CT scan of the eye': it uses light waves to create very high-resolution cross-sectional images (5-10 micrometres) of the retina. It is non-invasive and painless, and takes a few minutes.
It is the essential test for diabetic macular oedema: it measures the thickness of the retina precisely, identifies fluid build-up, and detects detachment of the neurosensory retina. Indispensable for monitoring the effectiveness of anti-VEGF injections.
What OCT detects
- Macular thickness and presence of oedema
- Intraretinal cysts and subretinal fluid
- Epiretinal membranes and vitreous traction
- Atrophy of the outer retinal layers
- Response to drug treatment over time
- 03
OCT angiography
Vessels without contrastAn advanced version of OCT that shows the network of retinal blood vessels without the need to inject a contrast agent. It allows the different vascular layers to be studied separately (superficial plexus, intermediate plexus, deep plexus, choriocapillaris).
It is particularly useful for detecting areas of capillary ischaemia, hidden neovessels and early changes in capillary density, even before they become visible on fundus examination.
When it is used
Excellent in patients who find it hard to cooperate, or who are allergic to the dye, because it does not require intravenous injections. Limitation: it does not show leakage (fluid leaking out), so in some cases conventional fluorescein angiography remains essential.
- 04
Fluorescein angiography (FA)
Dynamic vascular studyThis test requires an intravenous injection of a fluorescent dye (sodium fluorescein). A sequence of photographs follows the dye as it travels through the retinal vessels, showing in real time any leakage, blockages or neovascularisation.
It remains the reference test for studying retinal circulation in detail and guiding laser treatment in complex cases.
What it shows
- 05
Indocyanine green (ICG) angiography
Deep choroidIt uses a second dye (indocyanine green) that allows the deep choroidal circulation beneath the retina to be studied. Fluorescein and indocyanine green are complementary: the first is excellent for the retina, the second for the choroid.
It is carried out when a detailed assessment of the deep circulation is needed, for example in complex diabetic macular oedema or when associated choroidal neovascularisation is suspected.
Why both tests
Fluorescein angiography and indocyanine green angiography complement each other, providing different but integrated information about the circulation of the eye. Fluorescein shows the retina, indocyanine green shows the deeper layers. Together they guide treatment decisions in complex cases.
- 06
Functional tests and Amsler grid
Self-monitoringVisual acuity measured in clinic (Snellen charts, ETDRS) tracks visual function over time and is a key measure for assessing response to treatment.
The Amsler grid is a simple test that the patient can carry out at home: a grid with a central dot that helps to detect distortion, waviness or dark patches (scotomas) early — signs typical of diabetic macular oedema. It is a valuable self-monitoring tool between one visit and the next.
How to use the Amsler grid
- Hold the grid 30 cm away, with your usual optical correction (glasses or lenses)
- Cover one eye at a time — the other eye looks at the central dot
- Check whether the lines are straight or wavy, and whether there are any missing areas
- Do the test at least once a week
- Contact your ophthalmologist straight away if you notice new distortions or spots
Diagnostic criteria
Diagnosis of diabetic retinopathy is based on the combination of clinical examination and imaging. The stage and the presence of macular oedema determine the treatment strategy.
Established diabetic retinopathy
The diagnosis is certain when typical retinal vascular changes are present, even without symptoms:
- Microaneurysms, retinal haemorrhages or exudates on fundus examination
- Areas of capillary non-perfusion on fluorescein angiography or OCT angiography
- Macular oedema visible on OCT or fluorescein angiography
- Neovessels on the retina or iris (proliferative form)
When close monitoring is needed
In some cases more frequent follow-up is needed to detect progression at an early stage:
- Diabetes with poor blood sugar control (HbA1c >8%) without obvious signs
- Appearance of visual symptoms (floaters, distortion), even minor ones
- Pregnant woman with diabetes
- Starting a new diabetes treatment with rapid improvement in blood sugar
Frequency of check-ups
The schedule of eye check-ups depends on the type of diabetes and the stage of retinopathy. The ophthalmologist tailors it case by case.
Type 1 diabetes — no retinopathy
Guidelines recommend the first check within 5 years of diagnosis of diabetes; the ophthalmologist then sets the frequency.
Type 2 diabetes — no retinopathy
Guidelines recommend an eye examination already at diagnosis of diabetes; the ophthalmologist then sets the frequency.
Pregnant women with diabetes
Check in the first trimester, repeated during and after pregnancy if indicated.
Mild non-proliferative retinopathy
Regular check-ups with fundus examination and, if indicated, OCT, at the frequency set by the ophthalmologist.
Retinopathy with macular oedema under treatment
Closely spaced examinations and OCT, at the frequency set by the ophthalmologist, to assess the response to anti-VEGF injections.
Proliferative retinopathy
Closely spaced check-ups until stabilised with laser and/or injections.
Early diagnosis saves sight
Diabetic retinopathy is a major cause of blindness but is largely preventable with careful control of diabetes and regular eye examinations. Do not wait for symptoms: by the time they appear, the damage is often already advanced.