Pathophysiology of Age-Related Macular Degeneration Flashcards
What are the clinical signs of ‘Dry’ (non- exudative) changes?
- Drusen: hard, soft, confluent, reticular
- Hypo/hyperpigmentation
- RPE detachment
- Geographic atrophy/chrodial atrophy
What are the clinical signs of ‘wet’ (exudative) changes?
- CNV
- RPE detachment
- Subretinal fluid/haemorrhage
- Disciform scar formation
What happens when the Macula ages?
- Accumulation of lipofuscin in RPE (autofluorescence) and slow RPE loss
- Deposits between the RPE membrane and basal lamina
- Deposits between basal lamina and Bruch’s membrane
- Collagenous thickening and membrane bound deposits in bruch’s membrane
- Decrease in choriocapillaris ‘density’
What are subretinal deposits?
- Earliest detectable histopathology changes in ageing/AMD
- There are basal lamina (BlamD) and basal linear (BlinD) deposits
What are the basal lamina (BlamD) deposits?
Between the RPE membrane and RPE basal lamina
- they are larger, related to pigment changes?
- often contain membranous material
What are basal linear (BlinD) deposits?
Between the RPE and basal lamina and collagenous layer of bruch’s membrane
- related to drusen and pigment changes?
- contain coated droplets and membranous material
What is hard drusen?
Clinically appear to correlate with small, smoothly staining, regularly shaped bodies
What is soft drusen?
Clinically appear to correlate with larger, irregularly stained and shaped ‘fluffier’ bodies
- Much more irregular in staining and density and low mag than hard drusen
What is drusen confluence and heterogeneity?
- Hard drusen change with age
- Break down and merge to form ‘softer’ structures
- drusen can also regress over time
What are the material contained in drusen?
- Lipofuscin contains time-related aggregation of lysosome and mitochondrial by products
- Choriocapillaris also donates many blood borne products to sub RPE space over time
- Different forms of cholesterol contribute to products
- Immune system responds to presence of components of deposits
What is the composition of Drusen?
Both soft and hard drusen contain apolipoproteins and cholesterol
What is the composition of drusen?
Complement proteins C3 and C5 along with IgG antibodies and HLA-DR proteins bind to the drusen and associated deposits in the sub-RPE space
What is geographic atrophy?
Intracellular accumulations, extracellular deposits and immune response result in atrophy and necrosis of RPE
- It is the chronic progressive degeneration of the macula, as part of the late stage of AMD
What is choroidal neovascularisation?
- Seems to be degradation on inner (retinal) aspect of Bruch’s membrane
- New vessels start to grow from choriocapillaris into subretinal space
- Leak and lead to fluid or blood below retina
