What Is Diabetic Retinopathy and How It Causes Blindness
Diabetic retinopathy is the world's leading cause of preventable blindness in working-age adults. Here's how high blood sugar silently destroys the eye — and what medicine can do about it.
A Silent Thief of Vision
Most people with diabetic retinopathy don't know they have it. In its early stages, the condition produces no pain, no blur, no warning. Yet it quietly dismantles the intricate network of blood vessels feeding the retina — the light-sensitive tissue at the back of the eye — until one day, vision starts to fail.
Diabetic retinopathy is the leading cause of preventable blindness among working-age adults worldwide. According to a major systematic review published in Ophthalmology, roughly 103 million people were living with the condition as of 2020, and that number is projected to rise to 160 million by 2045 as diabetes rates continue to climb globally.
What Goes Wrong in the Eye
The retina demands a constant, rich supply of oxygen and nutrients delivered through a dense mesh of tiny blood vessels. When blood sugar remains chronically elevated — as it does in poorly controlled diabetes — those vessels are slowly damaged. Their walls weaken, they swell, they leak. Over time, the retina is starved of oxygen.
In response to this oxygen shortage, the body triggers the growth of new blood vessels. But these replacement vessels are fragile and abnormal: they bleed easily, scar, and can pull the retina away from the back of the eye entirely. That final stage — a retinal detachment — can cause permanent blindness if not treated quickly.
Researchers at University College London recently identified a protein called LRG1 as an early driver of this damage. Publishing their findings in early 2026, the team showed that LRG1 constricts the tiniest retinal blood vessels and cuts their oxygen supply before any of the classical signs of retinopathy appear — suggesting there may be a window to intervene far earlier than current treatments allow.
The Four Stages
Clinicians divide diabetic retinopathy into four progressive stages:
- Mild nonproliferative (NPDR): Tiny bulges, called microaneurysms, form in the walls of retinal blood vessels. They may leak small amounts of fluid.
- Moderate NPDR: Blood vessels begin to swell and lose their ability to transport blood normally.
- Severe NPDR: Large areas of the retina lose their blood supply, triggering signals for abnormal new vessel growth.
- Proliferative DR (PDR): New, fragile blood vessels sprout across the retina and into the vitreous gel of the eye. Bleeding and scarring can lead to severe vision loss or blindness.
A related complication — diabetic macular edema (DME) — can occur at any stage. It happens when leaking fluid accumulates in the macula, the central region of the retina responsible for sharp, detailed vision, and is one of the most common causes of vision loss in people with diabetes.
Who Is at Risk
Anyone with type 1 or type 2 diabetes can develop retinopathy, though the risk rises sharply with duration of the disease and poor blood sugar control. According to the National Eye Institute, nearly all people with type 1 diabetes will develop some degree of retinopathy within 20 years of diagnosis. High blood pressure, high cholesterol, pregnancy, and smoking all accelerate the damage. Prevalence is highest in Africa (nearly 36%) and North America and the Caribbean (33%), according to global data.
How It Is Treated
The most effective weapon against diabetic retinopathy remains prevention: keeping blood sugar, blood pressure, and cholesterol under tight control dramatically slows progression. Regular eye exams — at least annually for people with diabetes — allow early detection before vision is threatened.
When treatment becomes necessary, two main approaches are used. Laser photocoagulation (panretinal photocoagulation, or PRP) applies hundreds of small laser burns across the peripheral retina to seal leaking vessels and suppress abnormal growth. Anti-VEGF injections — drugs injected directly into the eye — block the protein that signals new vessel formation, and have become the preferred first-line treatment for diabetic macular edema. However, anti-VEGF therapy works in only about half of patients and does not reverse damage that has already occurred.
That limitation has made the LRG1 finding particularly significant. The UCL team has already developed a drug targeting LRG1, currently in preclinical trials, that could one day intercept retinopathy at its earliest molecular roots — before a single blood vessel leaks.
The Scale of the Challenge
With more than 500 million people living with diabetes worldwide — a number that keeps rising — diabetic retinopathy represents one of the most pressing public health challenges in ophthalmology. Most cases are preventable with screening and glycemic control, yet access to both remains uneven. Closing that gap, alongside developing earlier-acting therapies, will be central to protecting vision for tens of millions of people in the decades ahead.
