6.1.9 Macular degeneration Flashcards
What are the 5 stages of AMD?
- Early AMD
- Late AMD (dry)
- Late AMD (intermediate)
- Late AMD (wet active)
- Late AMD (wet inactive)
How does NICE classify AMD?
What are the 9 risk factors for AMD?
Age: 65 and over more at risk of AMD, with risk increasing with age
Genetics: FOH AMD are 4-6 x more likely to develop late AMD
Smoking: smokers are 2-3 times more likely to develop late AMD. In females 2.5 x more likely to develop wet AMD, in males 3.2 x
Hypertension: some evidence in association with late AMD
BMI and exercise: overweight/obese increases risk of late AMD, active lifestyle also has proactive effect against wet AMD development
Light: no evidence for increased risk of AMD due to light exposure but College says it is good to advise sunglasses with 100% UVA UVB protection in bright light environments
Gender: More recent evidence shows no evidence for more risk but previously it was thought women more than men (may be because women have longer life)
Race: previous studies said caucasians more at risk but recent evidence is inconclusive and NICE doesn’t say
Nutrition: diet low in omega 3 and 6, vitamins, carotenoid and minerals is a risk factor for AMD. eat a balanced diet with coloured fruit and vegetables and dark leafy veg, increase intake of oily fish, Evidence it can improve depending on the stage:
- No AMD or early AMD: no evidence for reduced risk with nutritional suppplements
- Intermediate and/or late AMD: mod quality evidence for reduced risk of progression in px taking AREDS (vitamin C/E, beta-carotene, zinc, copper) or AREDS2 ( AREDS without beta-carotene, with omega 3 fatty acids, lutein and zeaxanthin) formulation (no difference between both in delaying but ARERDS is contraindicated in smokers as beta-carotene increases risk of lung cancer) or antioxident supplements.
What are the layers of the retina, starting from the vitreous cavity?
vitreous cavity inner limiting membrane nerve fiber layer ganglion cell layer inner plexifrom layer inner nuclear layer outer plexiform layer outer nuclear layer outer limiting membrane photoreceptor layer retinal pigment epithelium Bruch's membrane choroid
Where is the choroid and what is the function?
The choroid is beteen the sclera and retina, it sits below Bruch’s membrane and is made up of choroidal vessels that supply the outer retina- it is important at the macula where retinal circulation is absent
provides 2/3 nutrition to the retina and RPE
What is the purpose of the macula and what is the anatomy?
It has the highest concentration of photoreceptors and gives high resolution central and colour vision
horizontally oval and 5 mm in diameter. The foveola is the central floor with a diameter of 0.35mm and is the thinnest part of the retina- thickness is only cone photoreceptors (outer plexiform layer containing Henle fibrrs, cytoplasmic extensions of foveal cones)
What is the purpose of the RPE and the anatomy?
The RPE maintains the photoreceptors- it absorbs stray light and forms the outer blood retinal barrier, it also regenerates the visual pigment
It is the highly pigmented layer of the retina which sits between Bruch’s membrane and the neurosensory retina
It is the most metabolically active at the macula (as this is where there is the highest concentration of photoreceptors and retinal circulation is absent); this is also the area where it is most likely to suffer consequence of RPE failue due to the accumulation of metabolic debris and lipofuscin
Where is Bruch’s membrane and what is the purpose?
It lies between the choroid and RPE
It controls the exchange of nutrients and waste products
Where is the neurosensory retina and what is it?
It is a collection of retinal layers including the retinal nerve fiber layer down to the photorecepto layers- it includes all retinal layers about the RPE
What is the foveal pit?
It is the centre of the macula and enables detailed colour vision
It has a large number of cone photoreceptors and no ganglion cells overlying them
How does AMD develop?
Undigested metabolic debris and lipofuscin accumulates beneath the retina between Bruch’s membrane and the RPE
In older eyes the debris are not removed and they form drusen (it is thought there may be an inflammatory response element to this)
What is dry AMD?
- It is the early and intermediate stages of the disease
- Debri build up causes drusen formation and degeneration of RPE
- Slow and progressive thinning and degerenation of the photoreceptors and RPE leads to failure of central vision
- 90% only mild to mod gradual visual loss
- Less aggressive but causes about 20% of AMD related severe visual loss
What are dry AMD clinical features?
Drusen:
-many large soft drusen= more likely to develop atrophy and severe visual loss= greater risk of developing wet AMD
Pigmentary abnormalities:
-Hypopigmentation: lighter area of retina compared to rest, this in combination with drusen increases risk of progression to late AMD
-Hyperpigmentation: darker areas of retina compared to surround, this in combincation with drusen increases risk of progression to late AMD
What are the two types of drusen?
soft and hard drusen
What is geographic atrophy and what do px experience?
- One or more areas of RPE hypopigmentation
- loss of overlying photoreceptors with clearly visible choroidal vessels and large area of retinal dysfunction
- 10% people with dry AMD develop GA
- bilateral in 50%
- severe visual loss- especially if at or near the fovea (blank patch in centre of vision))
