Aged Related Macular Degeneration Flashcards
What is age related macular degeneration (AMD)?
Age-related macular degeneration is a condition where there is degeneration in the macula that cause a progressive deterioration in vision. In the UK it is the most common cause of blindness.
A key finding associated with macular degeneration is drusen seen during fundoscopy.
What are the 2 types of AMD?
There are two types, wet and dry. 90% of cases are dry and 10% are wet. Wet age-related macular degeneration carries a worse prognosis.
Briefly describe the anatomy of the retina
The macula is made of four key layers. At the bottom, there is the choroid layer, which contains blood vessels that provide the blood supply to the macula. Above that is Bruch’s membrane. Above Bruch’s membrane there is the retinal pigment epithelium and above that are the photoreceptors.
What are Drusen? What is the significance of this?
Drusen are yellow deposits of proteins and lipids that appear between the retinal pigment epithelium and Bruch’s membrane.
Some drusen can be normal. Normal drusen are small (< 63 micrometres) and hard. Larger and greater numbers of drusen can be an early sign of macular degeneration. They are common to both wet and dry AMD.
What features are present in wet and dry AMD?
Drusen are common to both wet and dry AMD.
Other features that are common to wet and dry AMD are:
- Atrophy of the retinal pigment epithelium
- Degeneration of the photoreceptors
Briefly describe wet AMD
In wet AMD there is the development of new vessels growing from the choroid layer into the retina. These vessels can leak fluid or blood and cause oedema and more rapid loss of vision. A key chemical that stimulates the development of new vessels is vascular endothelial growth factor (VEGF) and this is the target of medications to treat wet AMD.
How is vision affected in AMD?
Note: early, intermediate and late
It is characterised by distinct clinical stages including early and intermediate AMD with drusen (yellow deposits under the retina made up of lipids and proteins) and macular pigmentary changes, usually associated with normal or near-normal vision; and late AMD, which is associated with a decrease or loss of central vision.
What are the risk factors of AMD?
- Age
- Smoking
- White or Chinese ethnic origin
- Family history
- Cardiovascular disease
What are the visual changes that may occur in AMD?
There are some key visual changes to remember for spotting AMD in your exams:
- Gradual worsening central visual field loss
- Reduced visual acuity
- Crooked or wavy appearance to straight lines
Which AMD presents more acutely? Wet or dry?
Wet age-related macular degeneration presents more acutely. It can present with a loss of vision over days and progress to full loss of vision over 2-3 years. It often progresses to bilateral disease.
What are the clinical features of AMD?
- Sudden-onset blurring or distortion of vision
- Drusen
- Macular pigmentary changes
- Geographic atrophy
- Choroidal neovascularisation
What are the signs of AMD found on examination?
- Reduced acuity using a Snellen chart
- Scotoma (a central patch of vision loss)
- Amsler grid test can be used to assess the distortion of straight lines
- Fundoscopy. Drusen are the key finding.
What investigations should be ordered for AMD?
- Slit-lamp biomicroscopic fundus examination
- Optical coherence tomography
- Fluorescein angiography
What is the role of optical coherence tomography in diagnosing AMD?
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.
What is the role of fluorescein angiography in diagnosing AMD?
Fluorescein angiography involves giving a fluorescein contrast and photographing the retina to look in detail at the blood supply to the retina. It is useful to show up any oedema and neovascularisation. It is used second line to diagnose wet AMD if optical coherence tomography does not exclude wet AMD.
