Aunt Zhang had lived with diabetes for ten years. She always felt that "high blood sugar is no big deal," checked her glucose only now and then, and never once had an eye examination. When her vision began to blur, she assumed it was the early stage of cataracts and did not see a doctor.

Then, last week, she suddenly found she could no longer see. Rushed to the hospital's eye department, she was diagnosed with advanced diabetic retinopathy. The doctor sighed: "If we had screened two years earlier and intervened in time, we could have preserved useful vision. Now the best window has passed, and the vision is very hard to recover."

Yet this kind of regret plays out every single day in eye clinics.

Diabetic retinopathy (DR) is the leading cause of blindness among working-age adults. It does not strike suddenly. Instead, high blood sugar inflicts a slow, "boiling-frog" chronic injury on the blood vessels at the back of the eye.

So how exactly does high blood sugar damage the retina step by step, and ultimately threaten vision?

1. How Does High Blood Sugar Harm the Retina?

Leaking and Blocked Vessels

Long-term high blood sugar continuously damages the endothelial cells and pericytes of the retina's tiny blood vessels — think of pericytes as the "support structure" of the vessel wall. The vessel walls thin and bulge locally, forming microaneurysms. These fragile sacs are like "leaky pipes," allowing blood components to seep out and causing hard exudates and macular edema.

At the same time, the damaged vessels gradually narrow and their lumens collapse, eventually leading to vessel "blockage" and the formation of "non-perfusion areas," which deprive the retina of oxygen and nutrients.

A Disaster Triggered by a Distress Signal

The oxygen-starved retina releases large amounts of vascular endothelial growth factor (VEGF), attempting to "save itself" by growing new vessels. But these new vessels are structurally abnormal and extremely fragile. They rupture easily and bleed, causing vitreous hemorrhage (patients often describe "dark shadows drifting in front of the eyes"), and form fibrovascular tissue that pulls on the retina (like scar tissue), which can ultimately lead to retinal detachment and permanent blindness.

2. The Silent Progression: Symptoms and Staging

DR is divided into two main stages based on whether retinal neovascularization appears. From early vascular changes to late-stage blindness, progression can sometimes be very rapid. By the time vision drops, the disease may already be in its middle or late stage.

Non-Proliferative DR (Early and Middle Stages)

Figure 1 — Non-proliferative DR: scattered microaneurysms, small retinal hemorrhages, and cotton-wool spots.

Figure 2 — Non-proliferative DR: scattered microaneurysms and small retinal hemorrhages with exudates.

Figure 3 — Non-proliferative DR: extensive hard exudates in the macula with macular edema, scattered microaneurysms, and small hemorrhages with exudates.

Vision may be completely normal with no obvious discomfort — this is the most easily overlooked "silent stage," yet retinal vascular damage has already begun. The main features are retinal microaneurysms, hemorrhages, hard exudates, cotton-wool spots, and microcirculation changes.

Proliferative DR (Late Stage)

Figure 4 — Proliferative DR: optic-disc neovascularization, scattered microaneurysms, small retinal hemorrhages and cotton-wool spots, with inferior vitreous hemorrhage.

Figure 5 — Proliferative DR: numerous microaneurysms, scattered small hemorrhages with exudates, macular hard exudates and edema, and retinal neovascularization.

Figure 6 — Proliferative DR: vitreous hemorrhage with scattered small retinal hemorrhages.

Figure 7 — Proliferative DR: optic-disc and retinal neovascularization, pre-retinal and vitreous hemorrhage, with localized tractional retinal detachment.

The hallmark of this stage is the appearance of new vessels on the retina or optic disc, possibly accompanied by vitreous hemorrhage, fibrous proliferation, and tractional retinal detachment. Patients may experience a sudden drop in vision, floating dark shadows, fixed dark areas, or severe visual distortion — all signaling a high risk of vitreous hemorrhage or tractional retinal detachment.

Diabetic Macular Edema

This can occur at any of the stages above and is a common cause of vision loss. The main manifestation is blurred or distorted vision.

Key point: The transition from "non-proliferative" to "proliferative" is a critical turning point in disease severity. The purpose of regular screening is precisely to detect and intervene before the disease reaches the proliferative stage, or before sight-threatening complications (such as macular edema) develop.

3. Guarding Your Sight: Early Screening, Diagnosis, Treatment, and Lifelong Follow-up

Because DR is "symptomless yet damaging" in its early phase and "symptomatic yet hard to reverse" in its later phase, the key to protecting your sight lies in proactive screening and lifelong follow-up.

Screening Timeline by Population

  • Type 2 diabetes: undergo a first comprehensive eye examination at the time of diagnosis, and review at least once a year.
  • Type 1 diabetes: if diagnosed before puberty (age 12), begin annual screening at age 12; if diagnosed after puberty, have the first examination within 5 years of diagnosis, then follow up according to risk.
  • Gestational diabetes / pregnancy with diabetes: screen early, then follow up according to risk.

Treatment Approaches for DR

  • The foundation: controlling blood sugar, blood pressure, and blood lipids significantly delays the onset and progression of DR.
  • The core medication — anti-VEGF drugs (such as ranibizumab, aflibercept, conbercept, faricimab): by blocking VEGF, the central "destroyer," these are the first-line preferred treatment for diabetic macular edema.
  • Laser treatment: an important tool for controlling high-risk DR, effectively improving retinal ischemia and hypoxia.
  • Vitrectomy: for late complications such as non-absorbing severe vitreous hemorrhage or tractional retinal detachment, this surgery can salvage remaining vision.

The Doctor's Advice

  1. Control the "three highs" — stable blood sugar, blood pressure, and blood lipids are the root of slowing the disease.
  2. Have regular eye examinations even when vision is good, and follow your doctor's schedule for review.
  3. Take early symptoms seriously: blurred vision, distortion, or floating shadows mean seek care immediately.
  4. Follow treatment as prescribed — persist with anti-VEGF injections, and do not delay laser or surgery.
  5. Quit smoking and limit alcohol! Smoking and excessive drinking significantly accelerate DR worsening.

Every fundus screening is a "top-up" for your light.

Every standard treatment is an "escort" for your vision.

Do not let "I thought it was nothing" become a "lifelong regret."

Starting today: control the three highs, and book your eye examination.

Protect the clear world that belongs to you!

If you still have any questions about diabetic retinopathy, you are welcome to tap "Read original article" below for an online consultation. Shanghai University-affiliated Shanghai HePing Eye Hospital is here to safeguard your vision.