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macdegen [2020/02/22 10:55] (current)
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 +====== macular degeneration ======
 +
 +see also:
 +  *[[blurred_vision]]
 +  *[[https://​mdfa-s3fs-prod.s3-ap-southeast-2.amazonaws.com/​s3fs-public/​MDBooklet_2017-04_WEB.pdf|MD Foundation booklet]]
 +  *[[https://​www.mdfoundation.com.au/​content/​testing-amsler-grid|MD Foundation'​s free Amsler Grid for regular home testing of central visual loss]]
 +
 +
 +=====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 (([[https://​www.manchester.ac.uk/​discover/​news/​protein-closely-linked-to-commonest-cause-of-blindness/​]]))
 +  *the molecule TLR2 appears to be a critical bridge between oxidative damage and complement-mediated retinal degeneration (([[https://​www.sciencedaily.com/​releases/​2020/​02/​200220141727.htm]]))
 +
 +=====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 (([[https://​jamanetwork.com/​journals/​jama/​fullarticle/​1684847|JAMA 2013: The Age-Related Eye Disease Study 2 (AREDS2) Randomized Clinical Trial]]))
 +        * 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 (([[https://​www.ncbi.nlm.nih.gov/​pubmed/​22555112]]))
 +      * **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 (([[https://​www.ncbi.nlm.nih.gov/​pubmed/​23084240]]))
 +
 +
  
macdegen.txt ยท Last modified: 2020/02/22 10:55 (external edit)