Diabetic Retinopathy: The Eye Damage You Cannot Feel
Diabetic retinopathy is damage to the tiny blood vessels of the retina — the light-sensitive film at the back of the eye — caused by years of high blood sugar. It is the commonest cause of blindness in working-age adults, and its most dangerous feature is that it produces no symptoms at all until it is advanced. Vision stays perfectly normal while the vessels leak, close off and are replaced by fragile new ones, and by the time sight blurs, floaters appear or a shadow crosses the vision, damage has usually already been done. That is why everyone with type 2 diabetes needs the back of the eye examined or photographed at diagnosis and then at least once a year, and everyone with type 1 from about five years after diagnosis — whether or not their sight seems fine. The condition is treatable: laser and injections into the eye stop most sight-threatening disease from progressing, and treatment given in time preserves vision that would otherwise be lost. What treatment cannot reliably do is give back sight that has already gone, which is the entire argument for screening. Keeping blood sugar, blood pressure and cholesterol under control, and not smoking, slows the whole process down and is as important as anything an eye specialist does.
Health writers · Aslam Clinic
What diabetic retinopathy is
The retina is a thin, light-sensitive film lining the inside of the back of the eye. It works like the sensor of a camera: light falling on it is turned into signals that travel down the optic nerve to the brain. It is fed by some of the smallest blood vessels in the body, and small vessels are exactly what long-standing high damages first.
Years of high sugar weaken the walls of those capillaries. They begin to bulge — the little outpouchings an eye doctor sees are called microaneurysms — and then to leak fluid, fat and blood into the retina. Later, vessels close off altogether, and patches of retina are left short of oxygen. Starved retina sends out a chemical signal asking for a new blood supply, and the eye obliges by growing new vessels. Those new vessels are the problem rather than the solution: they are fragile, they grow in the wrong place, they bleed into the jelly that fills the eye, and the scar tissue that forms along them can contract and pull the retina off the back of the eye.
So there are two separate ways diabetes takes sight, and a person can have either or both. One is leakage at the macula, the small central patch of retina responsible for reading, faces and detail — fluid collects there, the retina swells, and central vision blurs. The other is the growth of new vessels, which threatens vision suddenly and catastrophically rather than gradually. Neither is painful. Neither announces itself.
Why it goes unnoticed until it is advanced
This is the part that catches almost everybody. The retina has no pain fibres, so nothing hurts. The eye also has enormous reserve: one eye quietly covers for the other, and the brain fills in small missing patches so convincingly that people do not notice them. Damage that is obvious in a photograph of the retina can sit behind vision that still reads the bottom line of the chart. By the time a person notices blurring, the changes are usually well established, and by the time they notice a shadow, something has already bled or detached.
That is the whole reason for . A retinal photograph or a dilated examination finds the disease at the stage where treatment prevents loss rather than at the stage where it tries to salvage it. The check takes a few minutes, is not painful, and is the only way to know.
The stages
Eye specialists grade what they see so that the right interval and the right treatment follow from it. The names vary a little between systems, but every system is describing the same progression.
| Stage | What the eye specialist sees | What you notice | What usually happens next |
|---|---|---|---|
| Mild non-proliferative (background) | A few microaneurysms — tiny bulges in the capillaries | Nothing at all | Annual review; the priority is sugar, and lipid control |
| Moderate non-proliferative | More microaneurysms, dot and blot haemorrhages, hard exudates of leaked fat | Usually nothing | Review at shorter intervals, often six to twelve months |
| Severe non-proliferative | Extensive haemorrhages, beaded veins, closed-off capillary beds | Usually nothing, sometimes mild blurring | Referral to an ophthalmologist; a high risk of progressing within a year |
| Proliferative | New, fragile vessels growing on the retina or optic disc, sometimes bleeding into the eye | Floaters, sudden blurring, or still nothing | Laser treatment, usually urgently, sometimes with injections |
| Diabetic maculopathy | Swelling () and leakage at the macula, seen best on an OCT scan | Blurred or distorted central vision, difficulty reading | Injections into the eye, sometimes focal laser |
Swelling at the macula
Diabetic macular oedema deserves separating out, because it is the commonest way diabetes actually reduces someone's reading vision, and because it can occur at any stage — including when the rest of the retina looks mild. Fluid leaking from damaged capillaries collects in the central retina and thickens it. Straight lines look bent, print looks smudged rather than dark, colours look washed out, and the change is often worse on some days than others.
It is diagnosed with an OCT scan, a quick photograph that produces a cross-section of the retina and measures its thickness. The same scan is what treatment is judged against, which is why it is repeated at follow-up visits.
What raises the risk
- Duration of diabetes. The strongest factor by far, and the one nobody can change. After twenty years, most people with diabetes have some retinopathy.
- Blood sugar control over years. Every point of brought down reduces the rate of progression. Control matters cumulatively; it is not undone or achieved in a month.
- . Independently accelerates retinopathy, and treating it slows it. This is one of the reasons blood pressure is taken at every diabetes review.
- Raised and . Particularly linked to the hard exudates that damage the macula.
- Kidney disease. and a rising travel with retinopathy; the same small vessels are affected in both organs.
- Smoking, naswar and other tobacco. Damages small vessels everywhere, including these.
- Pregnancy. Existing retinopathy can worsen quickly, so eyes are checked in each trimester. Gestational diabetes that appears in pregnancy does not carry this risk.
- . Common here, and it worsens the oxygen shortage the retina is already facing.
How it is found
Either an eye specialist looks at the back of your eye after dilating the pupil, or a camera photographs it and a trained grader reads the image. Both are looking for the same features. A reading of the vision chart is taken first, and an OCT scan is added if the macula looks involved. None of it is painful and nothing touches the eye, apart from the drops.
An eye test at an optician for spectacles is not the same thing and does not replace it. A refraction measures the focusing power of the eye; diabetic screening examines the retina. It is entirely possible to be given a correct new prescription for glasses on the same day as having untreated proliferative retinopathy.
| Situation | First check | Then |
|---|---|---|
| Type 2 diabetes, newly diagnosed | At diagnosis | At least once a year |
| Type 1 diabetes | About five years after diagnosis, or from age 12 | At least once a year |
| Any retinopathy already found | As arranged by the ophthalmologist | Every three to twelve months, depending on the stage |
| Planning a pregnancy with existing diabetes | Before conceiving | In each trimester and after delivery |
| Gestational diabetes | Not required for the eyes | Standard diabetes follow-up after delivery |
| Any sudden change in vision | Same day | As advised |
How it is treated
Mild and moderate retinopathy is not treated in the eye at all. It is treated in the rest of the body — sugar, blood pressure, lipids and tobacco — and watched. That can feel like being told nothing is being done, but it is the intervention with the largest effect on what happens over the following decade.
- Laser (panretinal photocoagulation). For proliferative disease. Fine laser burns are applied to the outer retina, which reduces the oxygen demand and makes the fragile new vessels shrink back. It is done awake, with anaesthetic drops, over one or more sittings. It is a sight-saving treatment rather than a sight-improving one, and it costs some peripheral and night vision in exchange for the central vision it protects. Most people accept that trade once it is explained.
- Focal or grid laser. Used for some patterns of leakage at the macula, more often now as an addition to injections than instead of them.
- Anti-VEGF injections. The main treatment for macular and increasingly for proliferative disease. A drug that blocks the growth signal is injected into the eye under anaesthetic drops. It is uncomfortable rather than painful, takes seconds, and is repeated — often monthly at first and less often later. Which drug is used depends on availability and cost, and is the ophthalmologist's decision.
- Steroid implants or injections. Used when injections of anti-VEGF are not suitable or not working. They can raise the pressure in the eye and speed up formation, so they are chosen selectively.
- Vitrectomy. Surgery to remove blood that has not cleared from inside the eye, or to release scar tissue pulling the retina off. Done under local or general anaesthetic in an operating theatre.
The honest is this: treatment given at the right time prevents most severe sight loss, and a great many people keep useful vision for the rest of their lives. Treatment given after the macula has been swollen for a long time, or after a retina has been detached for weeks, recovers far less. The difference between those two outcomes is usually the date of the appointment, not the skill of the surgeon.
What you can do yourself
- Go to the eye check even though you can see perfectly. That is the entire point of it. Put it in the same month each year — many people tie it to a birthday or to Ramadan so it is not forgotten.
- Work on the , steadily rather than in bursts. Our article on type 2 diabetes covers what actually moves that number.
- Take the blood pressure tablets. They are protecting the eye and the kidney as much as the heart, which is rarely explained when they are prescribed.
- Take the if one has been prescribed. Lowering reduces the fatty exudates that damage the macula.
- Stop tobacco in every form, including naswar, gutka and shisha.
- Have the urine checked for protein at your diabetes review. is a signal that the small vessels elsewhere, including in the eye, are under strain.
- Treat if you have it. It is common, easily missed, and makes retinal oxygen shortage worse.
- Check each eye separately, once a month. Cover one eye, look at a straight edge such as a door frame or the lines of a grille, then swap. New blurring, a missing patch or a bent line in one eye alone is worth an appointment. This is not a substitute for screening, but it does catch some changes between visits.
Getting the check done in Pakistan
Cost and travel are the two reasons people most often give for missing an eye check, and both have answers. Large charitable eye hospitals, including the Al-Shifa Trust hospitals and the Layton Rahmatulla Benevolent Trust network, provide retinal examination and much diabetic eye treatment free or at nominal cost, and public teaching hospitals in every major city run diabetic eye clinics. Many diabetes clinics now take a retinal photograph on site and send it for grading, which removes a separate journey. If a specialist visit is genuinely not possible this year, a photograph taken at a diabetes review is far better than nothing.
A word about what does not work: no eye drop, herbal preparation, vitamin course or dietary supplement has been shown to treat or reverse diabetic retinopathy. Preparations sold for this purpose delay the treatment that does work, and the retina does not wait.
When to see a doctor
Go to an eye emergency department the same day for sudden vision loss, a sudden shower of floaters, flashes of light, a curtain across the vision, or a painful red eye with blurring. Book an appointment within a week if your vision has become blurred or distorted over days or weeks, if reading has become harder, or if you have noticed a patch missing when you cover the other eye. And book a routine appointment now, whatever your vision is like, if you have and have not had the back of your eyes examined or photographed in the past twelve months — including if you have only just been diagnosed, and including if you feel entirely well. Bring your most recent , your blood pressure readings and a list of your medicines; the eye and the rest of your diabetes care are one problem, not two.
Common questions
Still not sure what to do?
Reading about a symptom only goes so far. A doctor who can ask you questions and examine you will get further in ten minutes than any article can.
