age-related macular degeneration Flashcards
what is AMD?
- degenerative disorder of the macula causing significant visual loss
- 5-6 mm round area centred on the fovea
what is the epidemiology of AMD?
. leading cause of irreversible visual impairment in the wester world
. responsible for 54% severe sight loss ( better eye worse than 6/60) in caucasian individuals
. one of the leading causes of certified vision loss in England and wales
. significant visual impairment (binoc 6/18 or worse ) in 4% aged 75+
what is the main pathogenic factors involved in AMD?
- oxidative stress is one of the main pathogenic factors involved in AMD?
how is AMD classified ?
- Dry
- atrophic/non-neovascular
- 90% diagnosed cases - Wet
- neovascular/exudative AMD
- 10% diagnosed cases
what is the changes that you see in early Dry AMD?
. drusen> 63 um
. RPE hyper/hypo pigmentation
. RPE atrophy
what are the changes that you see in late/advanced dry AMD?
. geographic atrophy (GA)
. sharply demarcated area of atrophy
what do you happens with wet AMD?
. choroidal neovascularisation (CNV), scarring (disciform)
. macular oedema
. sub retinal fluid(SRF)
- serous detachment of neurosensory retina
. RPE detachment (PED) or tear
. haemorrhages ( sub, intra pr pre retinal)
. exudates
. also includes
- retinal angiomatous proliferation (RAP)
- polypoidal choroidal vasculopathy ( PCV)
what is another classification of AMD?
- category 1-
.No AMD
.none or a few small drusen <63um - category 2
. early AMD
. multiple small drusen or few intermediate drusen (63-124 um) or RPE abnormalities - category 3
. intermediate AMD
. extensive intermediate drusen, and at least on large druse ( >125 um ) or GA not involving the centre of the fovea - category 4
. advanced AMD
. GA involving the fovea and/or or any of the features of neovascular AMD
what are the early stages - histopathology of dry AMD?
- Basal laminar deposits
- lipid deposition in Bruch’s membrane
- failure of RPE to process cell debris
- used as histopathological marker for AMD
what are drusen ?
. 1st clinically visible sign in AMD is drusen
. extracellular deposits between RPE and Bruch’s membrane
. derived from immune mediated and metabolic processes in RPE, consist of lipofuscin, amyloid, complement factors
. age related, common in 60+
what is hard drusen ?
. discrete, homogeneous , eosinophilic nodular deposits lying between the RPE and the inner collagenous layer of Bruch membrane
-tend to be small
what are soft drusen ?
. non-homogeneous, eosinophilic deposits with ill-defined margins
what are clinical features to consider with drusen?
- size
- small (hard) <63 um
- intermediate 63-125um
- large > 125 um - hard(discrete), soft or confluent
- associated with pigmentary changes?
- hypo- or hyper-pigmentation
what is confluent drusen ?
- mixture of small, intermediate and large drusen
- some of the larger drusen start to merge and become confluent
what are pigment changes as result of dry AMD?
- hyperpigmentation
- pigment clumping
what geographic atrophy ?
- its a sign of late Dry AMD
- its loss of RPE cells , which allows unmasking of the choroidal blood vessels
how to evaluate the risk of progression to wet AMD?
-what you are looking for is :
- large drusen:
one eye?: 1
both eyes?: 2
- pigment changes
one eye?: 1
- in both eyes?: 2
score:
0: 0.5%
1: 3%- risk
2: 12 %
3: 25%
4: 50%
- px with late AMD in 1 eye have about a 50% chance of developing advanced AMD in fellow eye within 5 year
what is the pathogenesis of wet AMD?
- thickening of Bruch’s membrane
- increase advance glycation and (AGEs) products
- increase in lipids and exogenous proteins - hydrophobic barrier between choroid and retina
- ischaemia
- release of vascular endothelial growth factor VEGF
- neovascularisation from choriocapillaris via breaks in Bruch’s membrane
what happens to the new vessels in the pathogenesis of wet AMD?
- new vessels from choroicapillaris penetrate RPE
- situated beneath neurosensory retina
- new vessels are thin and ‘ leaky’ = exudates present
- sub-retinal haemorrhage
- CNV - choroidal neovascular membrane
- sub retinal fluid (SRF)
- PED ( pigment epithelium detachment)
what is pigment epithelium detachment (PED)?
- PED = detachment of RPE from inner collagenous layer of Bruch’s membrane
- serous PED - orange dome shaped elevation , clearly defined edges
- fibrovascular PED - much more irregular
- drusenooid PED- shallower, develop from confluent large drusen
what is sub-retinal haemorrhage ?
- when bleed continues into sub- retinal space
- the overlying blood vessels are still visible
what is the prevalence of late AMD in uk?
. 2.4% in population > 50 yrs ( = 513,000 cases )
. 4.8% in population > 65 yrs
. 12.2% in population > 80 yrs
. number of people with late AMD predicted to rise to 680,000 by 2020
what are the risk factors of AMD ?
- increase in age
- genetics
. family history of AMD - smoking
. 3x more likely - cataract
evidence to suggest : . gender . diet . atheroscleosis . oxidative damage . phototoxicity . inflammation
what are the symptoms of dry AMD ?
- report gradual loss in central vision
- asymptomatic - tend to happen in one eye only - subtle
- distortion noticed on Amsler but not spontaneously reported
- sometimes Px reports distortion in later stages
what are the symptoms of wet AMD?
. sudden decrease in central vision
. monocular
. distortion
. positive blur in the centre of the vision - lines appear wobbly and not straight
what are the diagnostic tools in AMD?
- BCVA - best corrected vision in both eyes
- Amsler grid for looking signs of distortion
- reading speed
- micoperimetry - perimetry for the central area
- fundus binocular (VOLK)
- OCT
- FAF - fundus autofluorescence
- FA - fluorescein angiography
- multifocal ERG ( research tool )
what is the optometric management of dry AMD?
. px information - reassurance . low vision aids - high adds . prevention advice
what is the optometric management of wet AMD ?
. urgent referral if VA> 6/96
. VA< 6/96 not urgent referral
- advanced untreatable disease characterised by subretinal fibrosis and/or pigmentary changes
- direct referral to specialist macular clinic
what is the preventative measures of AMD?
- stop smoking
- anti-oxidant supplements
. in Px with advanced AMD in 1 eye, risk of progression to advanced AMD reduced by 25%
.e.g macular carotenoids - diet
- treatment of risk factors ( e.g. macular surgery)
what is the ophthalmic management of AMD?
- diagnosis
. fundus BIO + OCT + FA - intra-vitreal anti-VEGF injections
- surgery
. laser
. photodynamic therapy ( PDT) - low vision assessment
- referral to ECLO
- SI/SSI registration - sight impaired or severely sight impaired
what are treatments for AMD in the future ?
- macular translocation
. lens implant that enhances central vision - phase 2 clinical trail for treatment of dry AMD
. lampalizumab ( anti-factor D) - stem cell therapy
