Medicine – Diabetic Eye Disease

Diabetic eye disease refers to a group of ocular complications caused by chronic diabetes mellitus, particularly diabetic retinopathy and diabetic macular oedema. Chronic hyperglycaemia damages the small vessels of the retina, producing increased vascular permeability, retinal ischaemia, haemorrhage, and eventually abnormal new-vessel formation.

Diabetic retinopathy remains an important cause of preventable visual impairment and blindness in working-age adults, although the exact ranking varies between populations and has changed with improved screening and treatment.

1. Pathophysiology

Long-standing hyperglycaemia damages retinal capillary endothelial cells and pericytes.

This produces two major pathological processes:

Capillary leakage → retinal oedema, haemorrhage and hard exudates.

Capillary closure → retinal ischaemia → VEGF production → neovascularisation.

These mechanisms explain the progression from early non-proliferative disease to proliferative diabetic retinopathy.

2. Modern Classification

The older terms background retinopathy and pre-proliferative retinopathy remain useful for examination notes, but modern classification generally describes these stages as non-proliferative diabetic retinopathy (NPDR).

The broad progression is:

Non-proliferative retinopathy → severe NPDR → proliferative diabetic retinopathy.

Diabetic macular oedema can occur at various stages and is considered separately because it directly threatens central vision.

3. Background Diabetic Retinopathy

Background retinopathy represents relatively early retinal microvascular disease.

Visual acuity is often unaffected, particularly when the macula is not involved.

Typical abnormalities include:

Microaneurysms.

Retinal haemorrhages.

Hard exudates.

4. Microaneurysms

Microaneurysms are small outpouchings of weakened retinal capillary walls and are among the earliest clinically visible abnormalities of diabetic retinopathy.

On fundoscopy they appear as tiny red dots.

Their presence reflects diabetic retinal microvascular injury.

5. Retinal Haemorrhages

Damaged retinal microvessels can leak blood into the retina.

Haemorrhages may appear as dot-and-blot haemorrhages when located within deeper retinal layers.

Superficial haemorrhages may have a flame-shaped appearance, although flame haemorrhages are also commonly associated with other retinal vascular disorders.

6. Hard Exudates

Hard exudates are yellow-white deposits composed largely of lipid and protein material that has leaked from abnormal retinal vessels.

They frequently occur close to areas of microvascular leakage.

When they involve or surround the macula, they may indicate clinically important macular disease.

7. Vision in Background Retinopathy

An important clinical point is that significant retinal abnormalities may exist while the patient still has normal visual acuity.

Therefore, patients cannot rely on symptoms to detect early diabetic retinopathy.

This is why regular retinal screening is essential.

8. Pre-Proliferative Diabetic Retinopathy

The traditional term pre-proliferative retinopathy describes more severe non-proliferative retinal disease with increasing evidence of retinal ischaemia.

Important findings include:

Cotton-wool spots.

Venous dilatation and venous beading.

Intraretinal microvascular abnormalities (IRMA).

These findings indicate an increased risk of progression to proliferative disease.

9. Cotton-Wool Spots

Cotton-wool spots are fluffy white retinal lesions caused by focal ischaemia of the retinal nerve fibre layer.

They represent disruption of axoplasmic transport following microvascular occlusion.

Therefore:

Cotton-wool spots = retinal microinfarcts.

They are not specific to diabetes and can also occur in hypertension and several other vascular or systemic diseases.

10. Venous Beading

Venous beading refers to irregular changes in the calibre of retinal veins, producing alternating areas of narrowing and dilatation.

It is an important marker of significant retinal ischaemia and severe NPDR.

Increasing venous abnormalities indicate a greater risk of progression to proliferative diabetic retinopathy.

11. Intraretinal Microvascular Abnormalities

Intraretinal microvascular abnormalities (IRMA) are abnormal intraretinal vascular channels that develop in areas of retinal capillary non-perfusion.

They represent attempts to provide collateral circulation around areas of ischaemic retina.

IRMA remain within the retina, which helps distinguish them from true neovascularisation extending onto the retinal or vitreous surface.

12. Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is characterised by the development of new abnormal retinal blood vessels.

The underlying stimulus is severe retinal ischaemia.

Ischaemic retinal tissue releases angiogenic factors, particularly vascular endothelial growth factor (VEGF).

The sequence is:

Retinal capillary closure → retinal hypoxia → ↑ VEGF → neovascularisation.

13. Neovascularisation

New vessels may develop on or near the optic disc or elsewhere on the retina.

These vessels are structurally fragile and grow along abnormal tissue planes.

Unlike normal retinal vessels, they are particularly prone to bleeding and fibrosis.

This creates the major complications of proliferative diabetic retinopathy.

14. Type 1 and Type 2 Diabetes

Proliferative retinopathy has traditionally been particularly associated with long-standing type 1 diabetes, whereas diabetic macular disease is often emphasised in type 2 diabetes.

However, both PDR and diabetic macular oedema can occur in either type 1 or type 2 diabetes.

The major determinants include duration of diabetes, glycaemic control, blood pressure, renal disease and other vascular risk factors, rather than diabetes type alone.

15. Panretinal Photocoagulation

Patients who have undergone treatment for proliferative diabetic retinopathy may have visible panretinal photocoagulation (PRP) scars on fundoscopic examination.

PRP applies multiple laser burns to the peripheral retina.

By reducing the metabolic demand of ischaemic peripheral retinal tissue, it reduces the angiogenic drive and lowers VEGF production.

The aim is to cause regression of dangerous neovascularisation and reduce the risk of severe visual loss.

16. Advanced Diabetic Eye Disease

Untreated or progressive proliferative diabetic retinopathy can lead to advanced diabetic eye disease.

Important complications include:

Vitreous haemorrhage.

Tractional retinal detachment.

Neovascular, or rubeotic, glaucoma.

These complications can cause profound visual loss.

17. Vitreous Haemorrhage

Fragile new vessels can rupture and bleed into the vitreous cavity.

A vitreous haemorrhage may produce:

Sudden painless visual loss.

Floaters.

Cobweb-like shadows.

Hazy or severely obscured vision.

The degree of visual impairment depends on the amount of bleeding.

18. Tractional Retinal Detachment

Neovascularisation is accompanied by growth of fibrovascular tissue.

As this tissue contracts, it pulls mechanically on the retina.

The sequence is:

Neovascularisation → fibrovascular proliferation → contraction → traction on retina → tractional retinal detachment.

If the macula becomes detached, severe central visual loss may result.

19. Rubeosis Iridis

Severe retinal ischaemia can stimulate abnormal new blood vessels to grow on the iris.

This is called rubeosis iridis.

These vessels may subsequently extend into the anterior chamber drainage angle.

20. Rubeotic or Neovascular Glaucoma

Neovascularisation of the iris and drainage angle can obstruct aqueous humour outflow.

This causes marked elevation of intraocular pressure and produces neovascular glaucoma, historically called rubeotic glaucoma.

It can be painful, difficult to treat, and potentially devastating to vision.

21. Diabetic Maculopathy

Diabetic maculopathy refers to diabetic retinal disease involving the macula, the part of the retina responsible for detailed central vision.

A major manifestation is diabetic macular oedema (DMO/DME).

Damage to retinal capillaries increases vascular permeability, allowing fluid and lipid to accumulate within the macula.

22. Macular Oedema

Fluid accumulation causes thickening and swelling of the macula.

Because the macula is responsible for high-resolution central vision, macular oedema may cause:

Blurred central vision.

Difficulty reading.

Reduced fine visual detail.

Distortion of central images.

23. Hard Exudates at the Macula

Vascular leakage can also produce hard exudates around the macula.

These lipid deposits may form circinate patterns around leaking microaneurysms.

The original notes refer to multiple exudates as a macular star. A true macular-star pattern can occur with retinal vascular leakage but is not specific to diabetic retinopathy and is classically associated with disorders such as neuroretinitis and severe hypertensive disease.

24. Central versus Peripheral Vision

Macular disease predominantly damages central vision because the macula provides detailed central visual acuity.

Peripheral vision may initially remain relatively preserved.

Therefore:

Diabetic macular oedema → central visual loss.

By contrast, extensive peripheral retinal photocoagulation can reduce peripheral visual field and night vision as a trade-off for preventing more severe vision-threatening complications.

Treatment

25. Good Glycaemic Control

Good long-term glycaemic control is fundamental to preventing and slowing diabetic retinopathy.

Persistent hyperglycaemia increases retinal microvascular injury.

Therefore, reducing long-term glucose exposure reduces the risk of developing and progressing diabetic microvascular complications.

26. Blood Pressure Control

Hypertension accelerates retinal microvascular damage.

Effective blood-pressure management is therefore an important component of diabetic eye protection.

The patient should be managed for overall cardiovascular and renal risk rather than treating the eye in isolation.

27. Lipid Management

Abnormal serum lipid levels are associated with retinal vascular disease and hard exudate formation.

Appropriate management of dyslipidaemia/hypercholesterolaemia is therefore part of comprehensive diabetes care.

28. Smoking Cessation

Patients should be encouraged to stop smoking because smoking substantially increases overall cardiovascular and microvascular risk.

Smoking cessation also benefits the patient’s renal, neurological, and cardiovascular health.

29. Regular Retinal Screening

Regular retinal assessment is essential because diabetic retinopathy can become significant before the patient notices visual symptoms.

Depending on the healthcare system, screening may use digital retinal photography, dilated fundal examination, optical coherence tomography (OCT), or specialist ophthalmological assessment.

OCT is particularly valuable for detecting and quantifying diabetic macular oedema.

30. Focal or Grid Laser Treatment

Focal or grid retinal laser photocoagulation has historically been important in the treatment of diabetic macular oedema.

Laser can target leaking microaneurysms or areas of retinal thickening in selected situations.

However, management of diabetic macular oedema has changed substantially with the development of intravitreal therapy.

31. Anti-VEGF Therapy

An important modern addition to the original notes is intravitreal anti-VEGF therapy.

Agents targeting VEGF can reduce vascular leakage, macular oedema, and pathological neovascularisation.

Anti-VEGF therapy is now central to the treatment of many patients with centre-involving diabetic macular oedema and is also used in the management of proliferative diabetic retinopathy in appropriate circumstances.

32. Panretinal Photocoagulation

Panretinal photocoagulation (PRP) remains an important treatment for proliferative diabetic retinopathy.

Numerous laser burns are applied to the peripheral retina.

The objective is not to improve normal peripheral retina but to reduce the stimulus for pathological neovascularisation and thereby prevent catastrophic complications such as vitreous haemorrhage and tractional retinal detachment.

33. Vitrectomy

Advanced disease may require vitrectomy surgery.

Indications can include persistent or severe vitreous haemorrhage and tractional retinal detachment threatening or involving the macula.

During surgery, vitreous haemorrhage and abnormal fibrovascular tissue can be removed and retinal anatomy addressed as appropriate.

34. Diabetic Retinopathy – Note Form

Background/non-proliferative retinopathy: visual acuity may remain normal.

Microaneurysms: tiny red capillary outpouchings and an early visible sign.

Haemorrhages: commonly dot-and-blot retinal haemorrhages.

Hard exudates: yellow-white lipid deposits caused by vascular leakage.

Pre-proliferative/severe NPDR: increasing retinal ischaemia without true new-vessel formation.

Cotton-wool spots: retinal nerve fibre layer microinfarcts.

Venous beading: irregular retinal venous calibre indicating significant retinal ischaemia.

IRMA: abnormal intraretinal vascular channels associated with capillary non-perfusion.

Proliferative retinopathy: defined by neovascularisation.

Mechanism of proliferation: retinal ischaemia → increased VEGF → abnormal new vessels.

Advanced disease: vitreous haemorrhage, tractional retinal detachment and neovascular glaucoma.

Diabetic macular oedema: vascular leakage into the macula → impaired central vision.

Systemic management: optimise glycaemic control, blood pressure and lipid management and encourage smoking cessation.

Monitoring: regular diabetic retinal screening, with OCT when macular disease needs assessment.

Modern ocular treatment: anti-VEGF injections, laser treatment where appropriate, PRP for proliferative disease, and vitrectomy for selected advanced complications.

Key Clinical Pattern

Remember the progression as:

Microaneurysms → haemorrhages/exudates → cotton-wool spots + venous beading + IRMA → neovascularisation → vitreous haemorrhage/tractional retinal detachment.

The most important distinction is:

Non-proliferative diabetic retinopathy → abnormal existing retinal vessels.

Proliferative diabetic retinopathy → NEW vessels.

And remember:

Macular oedema → central visual loss.

Proliferative retinopathy → neovascularisation → vitreous haemorrhage + tractional retinal detachment + neovascular glaucoma.

A useful treatment pattern is:

Risk-factor control + screening → anti-VEGF for many cases of diabetic macular oedema → PRP for proliferative retinopathy → vitrectomy for selected advanced disease.