Diabetic retinopathy
How years of high blood glucose damage the retina’s small vessels, making them leak and close, why an oxygen-starved retina grows fragile new vessels, and how this causes swelling of the macula, bleeding and detachment.
By the end, you can
- Describe the retina’s blood supply and the blood-retinal barrier.
- Explain how hyperglycaemia damages retinal capillaries, pericytes and basement membrane.
- Relate microaneurysms, haemorrhages, exudates and macular oedema to leakage.
- Explain how capillary closure and VEGF lead to proliferative retinopathy.
- Explain why retinopathy is screened for before symptoms appear.
- Recognise the fundus appearances, grading systems and tests of diabetic retinopathy, and explain how glucose and blood pressure control, anti-VEGF drugs, steroids, laser photocoagulation and vitrectomy act on its mechanism.
What it is
Diabetic retinopathy is damage to the small blood vessels of the retina caused by diabetes. It progresses from non-proliferative changes (leaking and closing vessels) to proliferative retinopathy (new vessels growing from the retina). Diabetic macular oedema, swelling of the central retina from leakage, can occur at any stage and is the commonest cause of vision loss.
3 types to tell apart
- Non-proliferative (background, pre-proliferative)
- Microaneurysms, haemorrhages and exudates; later signs of ischaemia such as venous beading and cotton-wool spots.
- Proliferative
- New vessels on the optic disc or elsewhere, driven by ischaemia; risk of vitreous haemorrhage and detachment.
- Diabetic macular oedema
- Leakage thickens the macula; can occur at any stage and threatens central vision.
US spelling: oedema → edema, colour → color, fibres → fibers.
Normal function
The retina and its blood supply
The retina lines the back of the eye. Its central region, the , is packed with cones and gives sharp central and colour vision. At the , nerve fibres leave and the enters.
Branches of the central retinal artery and their capillaries supply the inner retina; the outer retina, with the photoreceptors, depends on the choroid behind it. The retina uses oxygen faster than almost any tissue.
Retinal capillaries form a blood-retinal barrier: their endothelial cells are sealed by tight junctions, wrapped by contractile pericytes and supported by a basement membrane, so fluid, proteins and lipids stay in the vessels.
Underlying change · Step 1 of 4
High glucose damages small vessels
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 2 of 4
Vessels leak and close
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 4
An oxygen-starved retina grows new vessels
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 4 of 4
Vision loss, and why screening works
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .