Diabetes

• What is type 1 diabetes

  What is the prevalence

  -10% of diabetics

  -auto-immune condition - cells that produce insulin are destroyed

  -typically develops before 40 in childhood
• What is type 2 diabetes

  -90% of all diabetic cases

  -occurs when body stops producing enough insulin or becomes resistant to effect of insulin produced (doesnt respond)

  -will require oral drugs of injections of insulin

  -strongly correlated with obesity

  -remains undetected for many years
• Which symptoms would both type 1 and 2 diabetes lead to if blood glucose levels are poorly controlled

  -urinating more often

  -feeling thirsty

  -feeling tired

  -lightheadedness

  -unexplained weight loss

  -itching around genitals

  -cuts heal slowly

  -blurred vision

  
  

  -these symptoms are usually more acute in type 1
• How does diabetes lead to blurred vision

  -due to metabolic changes related to blood glucose levels which change refractive index of lens

  
  

  -periods of hyperglycaemia (high blood glucose) increases glucose levels in aqueous - some of the glucose is metabolised by the crystalline lens
• Visual impairment facts about diabetes?

  - diabetes is the leading cause of preventable sight loss in the UK

  - 7% of new blind registrations in England and wales are caused by diabetes
• How many people with DM1 AND DM2 have diabetic retinopathy?

  50% of those with DM1

  25% of those with DM2
• How does diabetes increase the risk of glaucoma?

  Increases the risk by 1.5x
• How does diabetes increase the risk of cataract?

  Doubles the risk
• Explain how energy is released in the body?

  - we eat

  - nutrients enter the bloodstream via the intestines

  - the most important nutrient is glucose

  - starchy foods + simple sugars = rich glucose

  - glucose then enters the bloodstream and is passed to the cells

  - cells convert glucose into ATP

  - ATP is then broken down to release energy
• Which cells carry out the regulation of blood glucose levels?


  -cells of the Islet of Langerhans (within pancreas)

  -which secrete insulin
• What does insulin do?

  -stimulates cells to increase uptake of glucose

  -stimulates glucose uptake from blood, it is then stored as glycogen in liver

  
  

  -lowers blood glucose
• The balance of which two hormones dictate our blood glucose levels?

  Glucose

  Glucagon ( also within pancreas )
• Treatment for type 1 diabetics

  Daily insulin injections
• Treatments for type 2 diabetes (glycaemic control)

  -exercise

  -dietary changes

  -meds - metformin
• What is HbA1c


  -a measure of glycaemic control

  -chemical formed when glucose combines with haemoglobin

  
  

  -HbA1c measures identify the average blood plasma glucose conc. over prolonged periods
• What are non-diabetic HbA1c measures normally

  
  

  What is a safe HbA1c in a diabetic patient

  -non-diabetic - HbA1c should be <36mmol/l

  
  

  -diabetic - HbA1c ~ 48mmol/l is safe
• What is the main modifiable risk factor for type 2 diabetes

  -obesity

  
  

  -obese men 6x more likely than non-obese

  -obese women 13x more likely than non-obese

  
  

  
  

  -current rising incidence is due to rising obesity
• What is incidence and prevalence

  Incidence = probability of a patient being diagnosed with the disease during a period of time

  
  

  Prevalence = the total number of cases of disease existing in a population

  
  

  -prevalence continues to grow until mortality equals or exceeds incidence rate

  
  

  -1 in 14.5 chance of diabetic patient

  -prevalence of type 1 and 2 diabetes = 6.9%
• Define diabetic retinopathy


  'Diabetic retinopathy is a chronic progressive, potentially sight-threatening disease of the retinal microvasculature associated with the prolonged hyperglycaemia and other conditions linked to diabetes mellitus such as hypertension.
• What are the non-modifiable risk factors for diabetic retinopathy

  - duration of diabetes

  —> within 20 years all type 1 and 60% of type 2 will have DR

  
  

  -ethnicity

  —> south Asian and African Caribbean > Caucasians

  
  

  -social deprivation

  
  

  -gender

  —> 56% men and 44% women

  
  

  -age
• What are the modifiable risk factors for diabetic retinopathy

  -glycaemia - strong association

  
  

  -blood pressure - strong association

  > 40% of all type2 diabetic px are hypertensive

  
  

  -lipid levels (cholesterol levels)
• How does ethnicity effect risk of developing diabetes

  -risk of type 2 diabetes 2x higher in south asian and african caribbean compared to caucasian

  
  

  -prevalence of DR higher in south asian than caucasian 42% vs 38%
• How does social deprivation effect risk of developing diabetes

  -type 2 diabetes is strongly correlated with social deprivation

  
  

  -income, housing, education

  
  

  -better predictor than ethnicity of DR

  
  

  -those with greater social deprivation - more likely to suffer most vision loss

  
  

  -levels of social deprivation are positively correlated with the late presentation of more severe (proliferative) DR
• What is the prevalence of diabetes in the 2 genders

  -56% of men

  -44% of women
• How does the duration of diabetes affect development of DR

  Type 2

  -30% have DR at diagnosis

  -rising to 60% after 15 years

  
  

  Type 1

  -90% will have DR after 20 years

  
  

  
  

  with duration % of diabetic cases increases
• How does age affect development of type 1 and 2 diabetes

  Type 1

  -older = less likely to get diabetes

  
  

  Type 2

  -older = more likely to get diabetes
• How does glycaemia affect development of DR


  -there is a strong association of glycaemic control and progression of DR
• How does blood pressure affect risk of developing diabetes

  -around 40% of type 2 diabetics are hypertensive

  -proportion of type 1 diabetics with hypertension lower at 30% (lower age )

  
  

  -retinal signs ,microaneurysms, haemorrhaging, cotton wool, exudates strongly correlated with hypertension

  
  

  -control of blood pressure has been shown to greatly reduce progression of DR
• How do lipid levels affect development of DR

  -there is evidence that managing cholesterol levels with statins (meds) can slow progression of DR
• What are the microangiopathy changes caused by DR?

  -loss of pericytes

  -microaneurysm formation

  -increased vascular permeability

  -capillary occlusion
• What are the purpose of pericyte cells?

  -encircle the endothelial cell layer of the blood vessel wall

  -they provide vascular stability

  -control endothelial proliferation
• What happens when pericyte cells are lost due to DR?

  1. reduced vessel wall strength - leads to outward bulging of vessels - microaneurysms

  
  

  2. increased endothelial cells proliferation ( uncontrolled growth of new endothelial cells )
• What is the earliest visible sign of DR?

  -microaneurysms
• How does DR increase vascular permeability

  -hyperglycaemic changes and microvascular structural changes (pericyte loss and microaneurysm formation) leads to breakdown of blood-retina barrier

  
  

  -the tight junctions become compromised leading to exudative or wet retinopathy

  
  

  -harmful blood constituents enter surrounding tissue
• What are the blood constituents that can enter do to the compromised blood retina barrier?

  -RBCs - leading to intra-retinal dot, blot and flame haemorrhages

  
  

  -plasma/serous fluid - leading to focal/diffuse oedema - at the macula this is diabetic maculopathy or diabetic macular oedema

  
  

  -lipids - leading to hard exudates
• How does DR lead to capillary occlusion

  -the above factors lead to reduced retinal blood flow through the capillary bed

  
  

  -as pressure drops within vessel walls, capillaries cease to transport oxygenated blood to the surrounding tissues

  
  

  -closed/occluded capillaries also called 'capillary dropout
• What are the signs of capillary dropout/occlusion (not visible with ophthalmoscopy?

  -located in clusters near microaneurysms

  
  

  -areas of capillary closure typically in mid and far periphery rather than macula

  
  

  -size and location of capillary closure could show subsequent neovascularisation due to retinal ischaemia
• What causes localised areas of chronic retinal ischemia?

  -the combination of microangiopathy, exudation and non-perfusion
• What kind of retinal ischaemia does DR deal with?

  Chronic
• What is the first visible sign of retinal ischaemia

  -cotton wool spot