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macdegen

macular degeneration

Introduction

  • MD is the main cause of legal blindness in Australia, accounting for over 50% of cases and affects 1 in 7 over the age of 50 yrs, of which 17% experience visual impairment, and some 15% of Australians over 80yrs of age have visual loss due to MD
  • MD is a group of degenerative, progressive and painless retinal diseases that cause progressive loss of central vision
  • it is usually related to ageing (usually only seen in those over 50yrs of age) in those with genetic predispositions and lifestyle factors
  • visual impairment may go unrecognised if it is only in one eye - hence the importance of regular testing
  • appears to have an association with higher Factor H Related Protein 4 (FHR4 protein) levels in the blood FHR4 apparently activates the immune complement system and FHR4 activity appears to be regulated by genes on chromosome 1 - the same genes which are associated with AMD risk 1)

Aetiology

  • genetic factors
    • 70% of cases have a genetic link
    • those with a direct family member with MD have a 50% risk
  • lifestyle factors
    • smoking increases risk 3-4x and makes onset 5-10 yrs earlier than non smokers
    • hypertension may be a risk for wet MD
    • “healthy nutrition, weight and exercise” may have a role in reducing risk, or at least improving ability to manage the visual impairment affect on lifestyle
      • possible benefits of dietary AREDS based supplements appear to reduce risk by 20-25%
        • oral supplementation with the Age-Related Eye Disease Study (AREDS) formulation (antioxidant vitamins C and E, beta carotene, and zinc) has been shown to reduce the risk of progression to advanced age-related macular degeneration (AMD). Observational data suggest that increased dietary intake of lutein + zeaxanthin (carotenoids), omega-3 long-chain polyunsaturated fatty acids (docosahexaenoic acid [DHA] + eicosapentaenoic acid [EPA]), or both might further reduce this risk 2)
        • AREDS2 formula for daily dosing:
          • 80mg zinc as zinc oxide
          • 500mg vitamin C
          • 400IU vitamin E
          • 2mg copper as cupric oxide
          • 10mg lutein
          • 2mg zeaxanthin

Stages

early MD

  • asymptomatic phase
  • retinal epithelial pigment cells (RPE cells) normally form a layer between the retina and the choroid
  • MD is characterised by the build up of drusen under the layer of RPE cells and this can be seen on fundoscopy
  • not everyone with drusen will lose their vision, however, its existence does increase the chance of macular degeneration associated vision loss developing later
  • currently there are no therapies in this phase that prevent progression apart from lifestyle changes

late MD

  • this occurs when visual impairment commences and can be divided into two forms
  • dry, atrophic MD
    • gradual loss of retinal epithelial pigment cells (RPE cells) and when these cells die there is loss of retina above that area
    • currently there are no therapies to reverse this aspect
  • wet, neovascular MD
    • the RPE cells fail to stop choroidal blood vessels from growing through the RPE layer and into the retina
    • this results in formation of fragile blood vessels under and within the retina choroidal neovascularisation or CNV
    • these can leak fluid or cause haemorrhage and can cause sudden rapid, painless central vision loss
    • there is only a 2-4 week window of opportunity to treat these acute events and prevent them causing permanent visual loss and scarring
    • Intravitreal injection vascular endothelial growth factor Rx options for wet MD:
      • Lucentis (ranibizumab)
        • an anti-VEGF treatment introduced in Australia in 2007
        • monthly injections 3)
      • Eylea (aflibercept)
        • an anti-VEGF treatment introduced in Australia in December 2012.
        • dosed monthly or every 2 months after 3 initial monthly doses produced similar efficacy and safety outcomes as monthly ranibizumab 4)
macdegen.txt · Last modified: 2020/02/07 22:33 by gary1