29th May 2025

Diabetic eye disease

Patients diagnosed with T2DM should be immediately referred to their local eye screening service. Diabetic retinopathy presents as gradually decreasing visual acuity but in cases where vitreous haemorrhage occurs, patients will experience a sudden partial or complete loss of vision. Several complications of diabetic retinopathy may occur, which are discussed below.  

Diabetic retinopathy is caused by progressive microvascular damage in the eye due to chronic hyperglycaemia. Several observable changes are seen in fundoscopy:

• Arteriole microaneurysms – The earliest visible manifestation of diabetic retinopathy, appearing as small red dots on the retina. 
• Blot haemorrhages – Weakened capillary walls are more liable to rupture. Haemorrhages may be indistinguishable from microaneurysms by fundoscopy but sometimes have more irregular borders. Fundus fluoresceine angiogram can be used to distinguish between haemorrhages and microaneurysms.  
• Hard exudates – It is theorised that increased capillary permeability allows leakage of lipoproteins through the vessel wall to form hard exudates, seen as yellow patches on fundoscopy.
• Cotton wool spots – Small arteriole infarcts result in patches of retinal non-perfusion, seen as white/yellow patches on fundoscopy.
• Intraretinal microvascular abnormalities – communications between arterioles and venules, bypassing capillary beds.
• Venous beading – intermittent dilatations in the retinal venules producing an appearance of beads on a string.
• Neovascularisation – chronic retinal hypoperfusion simulates the production of vascular endothelial growth factor A, which over time will lead to the formation of vessels to supply the retina.
• Vitreous haemorrhage – The new vessels produced are more fragile and liable to larger haemorrhage into the vitreous cavity.

Diabetic retinopathy is categorised by the International Clinical Diabetic Retinopathy Disease Severity Scale:

Table 3: Staging of diabetic retinopathy

Adapted from StatPearls: https://www.ncbi.nlm.nih.gov/books/NBK560805/

Patients with diabetic retinopathy may develop several other ophthalmological pathologies:

• Diabetic macular oedema (DMO) – Increased capillary permeability can lead to the accumulation of exudative fluid in the macula, leading to deterioration in central vision. DMO can lead to blindness.
• Posterior vitreous detachment – The detachment of the vitreous membrane from the retina causes the patient reduced visual acuity, floaters and flashers. 
• Retinal detachment – Producing a dark shadow to fall over the patient’s vision, which they often describe as curtain-like.
• Amaurosis fugax – Describes a sudden but transient monocular loss of vision due to retinal ischaemia. Diabetic retinopathy increases the risk of retinal artery and vein occlusion, as well as atherosclerosis and dissection. 
• Cataracts – Diabetic patients are at a much greater risk of developing cataracts, where the lens becomes thickened and opaque leading to reduced visual acuity and clouding of vision.

Diabetics should be encouraged to attend screening annually and should be referred urgently if they experience a sudden visual loss or neovascularisation or vitreous haemorrhage is seen on fundoscopy. Management of NPDR involves good glycaemic control and modulation of risk factors to prevent progression. Patients with severe NPDR should be considered for anti-VEGF therapy to prevent progression to proliferative retinopathy. Pan-retinal laser photocoagulation can be used once neovascularisation occurs to destroy the vessels before they bleed. Surgery may be offered to relieve intraocular pressure caused by a large vitreous haemorrhage, as well as for cataracts and retinal/vitreous detachment.