Diabetic retinopathy: why do we examine the retina when your vision is still good?

Many people with diabetes ask us: "I can see well and nothing bothers my eyes, so why does my diabetes doctor keep asking me to have the back of my eye checked?" The honest answer is that diabetic retinopathy can progress in complete silence. The retina may already need treatment while vision is still excellent, and the patient may notice nothing until the disease is well advanced. That is why we consider regular examination the first line of defence for the sight of anyone with diabetes.

What does diabetes do to the retina?

The retina is full of very small blood vessels that nourish it. Raised blood sugar over long periods weakens the walls of these vessels, so they start to leak fluid or become blocked in some areas. When part of the retina is short of blood supply, it releases substances that stimulate the growth of new blood vessels. This may sound like a solution, but it is actually a problem, because these new vessels are fragile and bleed easily.

This leads to the two main problems that threaten sight:

Diabetic macular edema (swelling of the macula): fluid collects in the macula, the part of the retina responsible for reading and seeing detail, and vision becomes blurred or washed out. This swelling can occur at almost any stage of retinopathy (Wilkinson et al., 2003).

Proliferative retinopathy: the appearance of new vessels. They can bleed into the vitreous gel and cause a sudden drop in vision, and scar tissue can form with them, pulling on the retina and causing it to detach.

Is it common?

Yes. A review of dozens of population studies worldwide suggests that retinopathy affects about 1 in 5 people with diabetes. The same review found that the risk among people with diabetes in the Middle East was higher than among those in Asia (Teo et al., 2021).

In Egypt, a study carried out in two university hospitals found retinopathy in about 20% of patients with diabetes. But the most important figure in that study was that about 82% of patients did not know that diabetes can affect the eye (Macky et al., 2011). This was a hospital-based study, not a survey of the whole population, but it shows how large the awareness gap is.

The stages of retinopathy, simply

Eye doctors divide retinopathy into stages that help decide when to see the patient again and what treatment is needed (Wilkinson et al., 2003):

1. No retinopathy.
2. Non-proliferative retinopathy: mild, then moderate, then severe. There are changes in the vessels but no new vessels.
3. Proliferative retinopathy: new vessels have appeared.

Macular edema is assessed separately, because it can appear at any stage.

The regular check: what happens, and how often?

The check includes measuring vision, then examining the retina with the pupil dilated or photographing the retina, and optical coherence tomography (OCT) of the retina when needed. OCT is the scan that detects macular edema and measures the thickness of the macula precisely.

There is no single interval that suits everyone. The eye doctor sets the next check according to the stage of retinopathy, whether there is macular edema, and the patient's circumstances. The International Council of Ophthalmology has published follow-up schedules that take account of differences in resources between countries (Wong et al., 2018). Some situations call for closer follow-up, such as pregnancy in a woman with diabetes, or a cataract that blocks a clear view of the retina (Wong et al., 2018).

You should leave the check knowing three things: the stage of your retinopathy, whether you need treatment now or monitoring only, and the date of your next check.

What protects your eyes besides the eye doctor?

Treating the retina alone is not enough if blood sugar and blood pressure stay poorly controlled. Large clinical trials have shown this clearly:

• In type 1 diabetes, good blood sugar control reduced the development of retinopathy by about three quarters and its progression by more than half. At the same time it increased episodes of severe low blood sugar, which is another reason why sugar control should be supervised by your doctor (Diabetes Control and Complications Trial Research Group, 1993).
• In type 2 diabetes with high blood pressure, good blood pressure control clearly reduced worsening of the retina and loss of vision (UK Prospective Diabetes Study Group, 1998).

So working with your diabetes or internal medicine doctor is part of the treatment. Discuss your targets with them, and do not change your medicines yourself.

Treatment: each problem has its own treatment

Not every patient with retinopathy needs immediate treatment. Mild and moderate stages usually need regular follow-up and control of blood sugar and blood pressure. Treatment inside the eye depends on the problem that threatens sight.

Macular edema

If the edema involves the center of the macula and reduces vision, injections into the eye (anti-VEGF medicines, which block a vessel growth factor) are the first-line treatment in European guidelines. Steroid medicines inside the eye may be used in some long-standing cases that do not respond well enough (Schmidt-Erfurth et al., 2017). Vision improved with all three commonly used medicines in a large American trial, and the difference between them was clearer in patients who started with poorer vision (Wells et al., 2015). Over two years, a large review of dozens of trials found no important difference in vision between these medicines (Virgili et al., 2023). We explain this in detail in our article on diabetic macular edema.

If the edema involves the center but vision is still good, the decision needs discussion. In a clinical trial in exactly this group, vision loss after two years did not differ between those who started injections straight away, those treated with laser, and those who were closely monitored and started injections if vision dropped (Baker et al., 2019). In other words, careful monitoring can be an acceptable option for some patients, provided appointments are kept strictly.

How the injections are given, and their risks, are explained in our article on eye injections.

Proliferative retinopathy

Here the aim is to protect the eye from bleeding, scar tissue and detachment. There are two main options, and both work:

Panretinal laser photocoagulation (PRP): an established treatment with proven benefit, which reduced severe vision loss by at least half in the original trials (Diabetic Retinopathy Study Research Group, 1981). Its advantage is a long-lasting effect, but it can affect side (peripheral) vision in some patients (Gross et al., 2015).

Injections into the eye: in an American trial that lasted five years, average vision was similar with injections and with laser. However, the injection group had less loss of side vision and less macular edema, while needing many injections and visits (Gross et al., 2015; Gross et al., 2018). A British trial found slightly better vision with injections after one year (Sivaprasad et al., 2017).

Why do we ask about your ability to keep appointments?

Because the effect of the injections is temporary. One study found that patients treated with injections alone who then stopped attending for several months did worse than those treated with laser, and had more complications such as traction retinal detachment (Obeid et al., 2019). So we discuss with each patient the treatment options that suit their case, taking into account their ability to attend regularly, the cost, and their work and travel. The researchers themselves recommend considering these factors when choosing (Gross et al., 2018).

Severe non-proliferative retinopathy: should we treat early "to prevent" problems?

Some patients ask this. In a clinical trial, early injections reduced the development of serious complications, but did not improve vision after four years compared with careful monitoring and treatment when needed (Maturi et al., 2023). So preventive injections are not routine, and the decision is made case by case.

Bleeding that does not clear, or scar tissue pulling on the retina

Here the patient may need a vitrectomy to remove the blood and release the retina from traction.

If you have diabetes and need cataract surgery

People with diabetes, especially those with retinopathy, are more likely to develop macular edema after cataract surgery (Chu et al., 2016), and the retinopathy itself can progress after the operation (Lee et al., 2025). This does not mean avoiding surgery; it means planning it: getting the retina as stable as possible beforehand, then following it closely afterwards. We cover this in detail in our article on cataract surgery in diabetes.

Questions patients often ask

My vision is excellent. Do I really need the check?

Yes. Retinopathy can be present, and can even need treatment, before there are any symptoms.

Do the injections cure "diabetes in the eye" for good?

No. The injections control the edema or the new vessels and may need repeating, while control of blood sugar and blood pressure remains essential.

Does retinal laser weaken vision?

Panretinal laser can affect side vision in some patients (Gross et al., 2015). But its purpose is to protect the eye from severe vision loss that could happen without it (Diabetic Retinopathy Study Research Group, 1981).

Can I lose my sight because of diabetes?

Treatment at the right time greatly reduces the risk of severe vision loss (Diabetic Retinopathy Study Research Group, 1981). That is exactly why early detection and regular follow-up are so important.

Summary

Diabetic retinopathy is one of the most preventable causes of vision loss, provided it is found early. Regular examination of the retina, even when vision is good, control of blood sugar and blood pressure, and sticking to the treatment and follow-up plan are what protect your eyes most. No single approach suits every case: the choice between monitoring, laser, injections and surgery depends on the stage of the disease and on each patient's circumstances and ability to attend follow-up.

This information is for health education and does not replace a medical examination.