Diabetic

• Diabetes can manifest itself through several ophthalmic conditions, grouped under the term diabetic eye disease. Diabetic retinopathy is the most common.
• Diabetic retinopathy:

  • Characterised by damage to the microvasculature supplying the eye
  • Due to chronically high glucose levels
  • Insult to retinal cells
  • Can lead to a progressive deterioration in vision - blindness
• Cataracts and cranial nerve palsies are examples of other ophthalmic complications associated with diabetes. Diabetic individuals are also at an increased risk of retinal artery/vein occlusions.
• Pathophysiology:

  • Weakened vessels that rupture - microaneurysms or small haemorrhages
  • Increase vascular permeability - hard exudates on retina
  • Blood flow is compromised - release of VEGF - neovascularisation
  • Neovascularisation into the vitreous humour may culminate in widespread vitreous haemorrhage causing sudden and complete visual loss
  • Fibrovascular bundles can lead to fibrosis and retinal traction resulting in retinal detachment
• Risk factors:

  • Length of exposure to hyperglycaemia
  • Hypertension
  • Minority ethnic groups
  • Diabetic nephropathy
  • Pregnancy
  • Rapid improvement of blood sugars can increase progression
  • Hyperlipidaemia/hypercholesterolaemia
• In cases where patients develop symptoms, typical symptoms of diabetic retinopathy may include:

  • Floaters: the result of small haemorrhages obscuring areas of vision and usually self-resolving.
  • Blurred vision and distortion: central vision may be blurred if the macula is affected.
  • Decreased visual acuity: gradual, painless reduction in the quality of vision.
  • Loss of vision: a severe haemorrhage can result in a sudden complete and painless loss of vision.
  • Blindness: a culmination of the disease if left untreated and uncontrolled.
• Clinical exam:

  • Visual acuity
  • Fundoscopy
• Diabetic retinopathy can be split into three classes:

  • Non-proliferative
  • Proliferative
  • Diabetic macular oedema
• Non-proliferative:

  • Background retinopathy = presence of at least one microaneurysm
  • Pro-proliferative = Multiple microaneurysms with or without haemorrhages and hard exudates. Evidence of retinal ischaemia.
• Signs of non-proliferative retinopathy:

  • Microaneurysms
  • Dot and blot haemorrhages
  • Hard exudates
  • Cotton wool spots - due to chronic ischaemia
  • Venous beading
  • IRMAs - intraretinal microvascular abnormalities
• Proliferative diabetic retinopathy:

  • Characterised by new vessels on the disc and or new vessels elsewhere
  • Can present as neovascular glaucoma, pre-retinal fibrosis and tractional detachment
• Signs of proliferative retinopathy:

  • Neovascularisation
  • Vitreous haemorrhage
  • Retinal detachment
• Diabetic macular oedema:

  • Oedematous changes in or around the macula
  • Macula responsible for central vision - patients complain of blurred vision when reading or difficulty recognising faces
  • Most common cause of visual loss in diabetics
• Investigations:

  • Optical coherence tomography - cross sectional view of the retina
  • Fluorescein angiography - gold standard for visualising the vasculature of the retina
• Photocoagulation:

  • primary intervention for proliferative DR
  • Uses a laser to create numerous burns in the retina to destroy photoreceptors
  • Less photoreceptors decreases oxygen demand in the retina and endothelial cells express fewer growth mediators e.g. VEGF
  • There are two different methods to photocoagulation: focal/grid photocoagulation and pan-retinal photocoagulation (PRP).
• in persistent haemorrhage or in central, sight-threatening tractional retinal detachment a vitrectomy may be performed. This allows for the removal of the vitreous and repair of any scarring/detachment of the retina. 
• Diabetic retinopathy is one of several causes of neovascular glaucoma, a type of secondary glaucoma.

  • Neovascularisation within the iris and trabecular meshwork
  • Acutely painful, red eye
  • Vision loss