Flashcards in Age Related Macular Degeneration Deck (29)
What is the definition of sightlessness?
Having less than 1/10 of normal vision in the more efficient eye when refractive problems are fully corrected
What develops in retinopathy?
How do micro-aneurysms appear?
Outpouring of the retinal vasculature that appear as minute, unchanging red dots associated with blood vessels
How do micro-aneurysms occlude vision?
Leak plasma, resulting in localised oedema that gives the retina a hazy appearance
They also bleed - contributing to oedema
Affected vision if they encroach on the macula and cause degeneration before they are absorbed
How does neovascularisation occur?
Formation of new blood vessels from the choriocapillaries, entering between the pigment and sensory layer, or from the retinal veins, extending between the sensory retina and vitreous cavity and sometimes into the vitreous body
- growth factors, signalling systems and VEGF involved
How can neovascularisation causes problems with sight?
The vessel are fragile, lead protein and are likely to bleed
- blurred vision if covers the macular and can cause degeneration
What are opacities?
Loss of retinal transparency due to haemorrhages, exudates, cotton wool sports, oedema and tissue proliferation
- exudate result from inflammatory processes
How do exudate damage vision?
Destroy the underlying retinal pigment and choroid layer
What are cotton wool patches?
Retinal opacities with hazy irregular outlines
These occur in the nerve fibre layer and contain cell organelles
- retinal trauma
- severe anaemia
- diabetic retinopathy
What are the investigations that can be done to diagnose age related macular degeneration?
Funds fluorescein angiogram
- IV fluorescein injection
- fluorescein binds to albumin which remains in normal capillaries
- use blue and yellow filter to see details of retinal circulation
Optical coherence tomography
- low power laser interferometry
- generates detailed cross-section image of retina
Name and describe the two types of AMD.
- new blood vessel formation under retina/above choroid
- atrophy of outer retina
How does AMD cause blindness?
Blood vessels and scar tissue grow under the retina
Leaking vessels cause retinal oedema
This blocks transport of oxygen and nutrients from the choroid to the avascular macular
Eventual scarring causes destruction of photoreceptors
What are the risk factors for AMD?
Age (over 70)
Diet - high doses of vitamin A, C and zinc may be protective
What's the most common genetic cause of AMD?
Polymorphism sin complement factor H gene
- regulates inflammation and prevents complement mediated attach on own cells
- inflammation is significant in AMD
What are other genes that are thought to cause AMD?
Complement genes - CFB, CF1, C2 and C3
Lipids - genes for LDL and HDL
ECM - collagen and matrix metalloproteinase
What is thought to start the process of AMD?
Photoreceptors continue to produce photosensitive pigment throughout life
The ends of photoreceptor cells decay and are removed by retinal pigment epithelium constantly
- in some cases the end products accumulate causing drusen
- increases AMD risk
What is the best treatment for AMD?
Monoclonal antibodies that inhibit VEGF - to prevent neovascularisation
What are the licensed and unlicensed treatments for AMD?
Ranibizumab - licensed (more expensive)
Bevacizumab - unlicensed (less expensive)
How is ranibizumab administered?
Intravitreal injection by opthalmologists in a sterile room
How often is ranibizumab administered?
Once a month for three months
How many people on ranibizumab improved?
40% improved by 15 or more letters on a visual acuity test
What are the differences between ranibizumab and bevacizumab?
Injections given as required, not every month
Yearly cost of R=£9656 while B=£1509
What are the economic problems or blindness?
Unable to work - loss of employment and income
Requires increased care - more likely to be put in a nursing home
Finance - bank statements and bills
What are the problems people with independence that blind people have?
Health risks - falls and fractures
Domestic - cooking, eating, dressing and telephone
Navigation - safety
What are the problems with communication people with blindness have?
TV, film and media
What are the psychological problems people with blindness have?
What is visual acuity?
Recorded as: the distance chart is read/distance at which it should be read
What measures must be made when checking visual acuity?
Check if the patients needs distance glasses - get them to wear them
6 meters from the chart
One eye at a time
If vision is imperfect - use a pinhol