Week 18 - AMD Flashcards
Key features of the Macula
- Densely packed cone photoreceptors
- An absence of rods at the fovea
- Fovea is avascular and in this area the retina is supplied with oxygen which diffuses from the choroid to the foveal retina
- Fovea 1.5mm across
- Foveola 0.15mm diameter – cones most densely packed in this area
- Avascular zone 0.5mm diameter
- Half of the retinal nerves in the optic nerve serve the fovea
Describe AMD
- AMD: long-term degenerative condition
- Leading cause of visual impairment in the UK
~600,000 people diagnosed (UK) - AMD is relevant to optometrists as loss of sight can have impact on quality of life and emotional health
Statistics
Prevalence estimates for UK by age groups (all types of AMD):
50+ y: 2.4 %
65+ y: 4.8 %
80+ y: 12.2 %
Number of people with AMD predicted to rise
26,000 new cases each year (NICE estimate)
Key reasons: aging population, increase in life expectancy
Workload implications for HES
AMD and visual impairment
- Visual impairment (6/18 or worse) from AMD affects
4% of UK population > 75 years
14% of UK population > 90 years
1.6% have VA < 6/60 in population > 75 years
AMD Risk Factors - Nice Guidance
- Diet low in omega 3 and 6 and cartenoids and minerals is a risk of AMD
- Lack of exercise
- Smoking
- Older age
- Hypertension
- Family history of AMD
- BMI of 30 kg/m2 or higher
- Presence of AMD in the other eye
- High fat diet
Dry AMD
- More common
- Slowly progressing
- No sudden loss of vision
- Managed by Optometrists in most cases
Dry AMD - NICE classification
Normal eyes
- No signs of AMD.
- Small (hard) drusen (<63 micrometres) only.
Early AMD
- Low risk of progression:
- Medium drusen (≥63 but <125 micrometres), or
- Pigmentary abnormalities.
Medium risk of progression:
- Large drusen (≥125 micrometres), or
- Reticular drusen, or
- Medium drusen with pigmentary abnormalities.
High risk of progression:
- Large drusen (≥125 micrometres) with pigmentary abnormalities, or
- Reticular drusen with pigmentary abnormalities, or
- Vitelliform lesion without significant visual loss (best-corrected acuity better than 6/18), or
- Atrophy <175 micrometres and not involving the fovea.
Late AMD (dry)
- Geographic atrophy (in the absence of neovascular AMD).
- Significant visual loss (6/18 or worse) associated with:
Dense or confluent drusen, or
Advanced pigmentary changes and/or atrophy, or
Vitelliform lesion.
Define Reticular Drusen
• Drusen: sub retinal pigment epithelium deposits
• extracellular debris composed of lipids and proteins which sit just below the RPE, or between the RPE and bruchs membrane
• Reticular drusen are also known as pseudo-drusen or subretinal drusenoid deposits.
• Contrary to the drusen which lie below the retinal pigment epithelium (RPE), reticular drusen are located superficial to the RPE.
• They are yellowish subretinal lesions arranged in a network and indicate a greater risk of AMD progression
Vitelliform lesion
• Accumulation of lipofuscin within the subretinal space
• Lipfuscin and extracellular deposit accumulation in drusen is below the RPE.
• Lipofuscin is is a heterogeneous material composed of a mixture of lipids, proteins, and different fluorescent compounds, the main fluorophore of which has recently been identified as a derivative of vitamin A
Dry AMD – the Role of the Optometrist
- Make the diagnosis
- Give relevant advice (including advice on driving and smoking cessation)
- Counselling – diagnosis is often a shock
- Provide Information – needs to be accessible (e.g. large print)
- Monitor – disease progression
Referral
Low Vision Services
For SI or SSI Registration (Ophthalmology)
To Social Services
Management of Dry ARMD
No treatment available
Advise on lifestyle modifications
Advise patients on nutritional supplements
Educate about symptoms of progression and self-monitoring
Aim: to slow down the progression
Management of dry ARMD: Emerging treatments in the US
• Complement Factor inhibitors
- FDA approved
- Intravitreal injections
- Monthly or bimonthly
- Utility has been shown in patients with severe dry AMD ( Geographic atrophy )
Nutritional Supplements – AREDS
- (Age-related eye disease study)
- Large scale, randomized, double-masked, placebo- controlled clinical trial (RCT)
- Looked at effectivity of supplements in delaying preventing onset progression of AMD
- antioxidant supplements reduced the risk of AMD progression in those with moderate/ high risk of progression
- But, a systematic review showed that supplements had no effect in the prevention of AMD
- Omega-3 fatty acids may help prevent AMD
Smoking cessation
- Smoking increases oxidative stress
- Second most important risk factor (after age)
- Most important modifiable risk factor
- Smoking:
Slows down choroidal blood flow
Promotes ischemia
Reduces macular pigment
Other lifestyle modifications
Increased physical activity > No direct evidence
Reduced alcohol consumption > Unclear whether moderate consumption is a risk
Reduction of waist-hip ratio > Especially in obese – unclear?
Diet rich in omega-3 polyunsaturated fatty acids > Evidence for decreased risk