Age Related Macular Degeneration Flashcards
Age-related macular degeneration
Degeneration in the macula that causes a progressive deterioration in vision
Types of macular degeneration
Dry - 90%
Wet - 10% (worse prognosis)
Fundoscopy findings for macular degeneration
Drusen
Hypo/hyperpigmentation of retina
Drusen
Yellow deposits of proteins and lipids that appear between the retinal pigment epithelium and Bruch’s membrane
Larger and greater numbers of drusen can be an early sign of macular degeneration
Normal drusen
Small (< 63 micrometres) and hard
Features of AMD
Drusen
Atrophy of the retinal pigment epithelium
Degeneration of the photoreceptors
Wet AMD
Development of new vessels growing from the choroid layer into the retina - choroid neovascularization
Vessels can leak fluid or blood and cause oedema and more rapid loss of vision.
What chemical simulates the growth of blood vessels in the choroid layer
Vascular endothelial growth factor (VEGF)
Risk factors for AMD
- Age
- Smoking
- White or Chinese ethnic origin
- Family history
- Cardiovascular disease
- Light iris
- Hyperopia - long sighted
Presentation for AMD
Gradual worsening central visual field loss
Reduced visual acuity
Crooked or wavy appearance to straight lines
Loss of contrast sensitivity and abnormal dark adaptation
Presentation of wet AMD
Presents more acutely
Loss of vision over days and progress to full loss of vision over 2-3 years.
It often progresses to bilateral disease
Central scotomas
Wavy lines
Examination for AMD
Snellen chart - Reduced acuity
Scotoma (a central patch of vision loss)
Amsler grid test -assess the distortion of straight lines
Fundoscopy - Drusen and global atrophy
Investigations for MD
Slit-lamp biomicroscopic fundus examination - diagnostic
Optical coherence tomography
Fluorescein angiography
Optical coherence tomography
is a technique used to gain a cross-sectional view of the layers of the retina. It can be used to diagnose wet AMD.
Fluorescein angiography
Giving a fluorescein contrast and photographing the retina to look at the retinal blood supply
Shows oedema and neovascularisation.
2nd line to diagnose wet AMD if optical coherence tomography does not exclude wet AMD.
Management of AMD
Refer suspected cases to an ophthalmologist for assessment and management.
Dry AMD management
No specific tx
Self monitor - Amsler grid
Lifestyle measures may slow the progression:
- Avoid smoking
- Control blood pressure
- Vitamin supplementation
Wet AMD management
Anti-VEGF medications - ranibizumab, bevacizumab and pegaptanib
VEGF blockers features
Injected directly into the vitreous chamber of the eye once a month.
Slow and reverse the progression of the disease.
Typically need to be started within 3 months to be beneficial
Early AMD
Few medium sized drusens
Pigment abnormalities
Intermediate AMD
1+ large drusens or several medium drusens
Geographical atrophy that does not extend to the macular centre
Advanced dry AMD
Drusen and geographical atrophy extend to the macular centre
Gradual vision loss
Why do drusens occur
Undigested cellular debris from the degeneration of RPE cells as apart of the normal ageing process
What can soft drusens do
Lift the RPE away from the Bruch’s membrane which can cause hypoxia and inflammation leading to choroid neovascularisation and therefore wet AMD
Progression from dry AMD to wet AMD
- Drusen formation
- Inflammation
- Macrophage recruitment
- VEGF secreted causing a signalling cascade
- Neovasularisation - Wet AMD
Geographical atrophy
Advanced map like area of atrophy extending to the foveal centre
Why does neovascularisation cause vision loss
- VEGF stimulates new blood vessels to extend through Bruch’s membrane
- Fluid and blood leaks beneath and into the retina
- Formation of fibrous scar tissue
- Central vision loss
Disciform scar
Disc like scar - causes a scotoma
Risk factors for the development of wet AMD
5+ drusens
Large soft drusens
Pigment clumping in the RPE
Systemic HTN
Fundoscopy changes for wet AMD
Exudate
Blood
Elevation of the retina - due to blood, fluid or fibrovascualr tissue
Cystic oedema of the sensory retina overlying choroid neovascularization
Charles Bonnet syndrome
Visual hallucinations - brain doesn’t receive as much visual stimulus therefore fills in gaps
