Stage 1 Visit 1 - AMD

Amsler Chart

• Sensitive assessment of the 20 degrees visual field

• Test carried out monocularly at 30cm - each square subtends 1 degree of visual angle

• Px need to wear correct reading Rx - NOT varifocals/bifocals

• Px focuses on central dot and reports areas of distortion/scotoma

Prevalence of AMD in over 75s?, DRY/WET

• Most common cause of irreversible visual impairment in the UK - increases exponentially with age

• 4.8% of over 65 have advanced AMD, rises to 12.2% of over 80s 

• 30% of over 75s are in someway affected by AMD 

• Very rarely detected before 50

• Dry AMD 90% of cases

• WET 10% - typically more acute and severe - may require urgent referral

Risk Factors for AMD

• AGE - strongest RF

• High BMI / History of cardiovascular disease / Hypertension - moderate association

• Caucasians more likely than Africans or Asians

• First degree relative with AMD - 3x more likely 

• Females

• Smoking - Single most powerful modifiable RF - 2x the risk of developing AMD

What protects a px from AMD?

Healthy diet, regular exercise, normal BP and controlled cholesterol levels

How will AMD appear?

• Bilateral, often asymmetric 

• Px with advanced AMD in one eye - 50% chance of advanced AMD in the fellow eye within 5 years

Why and How does AMD occur?

Ageing - causes an increase in thickness of Bruch’s membrane which reduces the permeability 

• This inhibits the removal of toxic metabolic waste such as Lipofuscin

• These waste products begin to accumulate between Bruch’s membrane and the RPE (drusen)

SX of AMD

• Bilateral - asymmetric and likely to be asymptomatic in the early stages

• Gradual deterioration of vision - over a number of years

• Advanced AMD - difficulty with visual tasks that require resolution of fine detail e.g reading/recognising faces

• In severe cases a positive central scotoma

SX exclusive to WET AMD

• Painless and sudden onset of blurred or distorted central vision - requires urgent referral - even if no retinal signs

• Initial onset in Px with WET AMD is unilateral BUT 37% develop in 2nd eye within one year

• Vision becomes distorted - metamorphopsia

Why does Metamorphopsia occur?

Due to the disruption of the organisation and orientation of the RPE and PRC by subretinal fluid

Signs of AMD

• Drusen - first visible sign in both forms - typically clustered around the macula

• Geographic Atrophy  - DRY AMD + WET AMD

• Choroidal NV - WET AMD

• Haemorrhages - WET AMD

What does Drusen do to the retinal layers?

• Elevates the RPE and distorts the structure+organisation of overlying retinal layers

• Due to the above = reduce VA

Geographic Atrophy

• Degeneration of RPE leads to ATROPHY - loss of sensory retina = devastating impact on VA especially if the fovea is affected

• END stage of DRY AMD

• Px can develop a positive central scotoma in the region of the GA

• Areas of GA can be identified by areas of retinal pallor

Why and How does CNV occur?

• The angiogenic stimulus (trigger for CNV to occur) is ischaemia

• Reduction in permeability of Bruch's Membrane = undersupply of oxygen to retina = new vessels arise from Choroid

• This is supported by the proliferation of the subretinal neovascular membrane which is the tissue underneath the retina - this membrane will appear grey-green-yellow in colour - only in WET

• This extends vessels of the choroid through defects in Bruch’s membrane to the sub-RPE space

• Some vessels breaks through the RPE and grow into the sub-Retinal space

Management for CNV?

Urgent referral even when haemorrhaging isn’t present as prognosis becomes poor once haemorrhage occurs

Optometric Management of Dry AMD

• If optometrist confident about diagnosis, px doesn’t require referral but made aware of sx - annual recall

• If not sure about diagnosis of Dry AMD - refer

• Refer if px is symptomatic as likely to need reassurance about their vision loss 

• VA can become severely impaired LVA assessment may be indicated - refer via GP

• Explain that AMD is a progressive condition and vision might start to deteriorate however the rate of progression is very slow - there is variability in different px in the rate of progression 

• Explain it will only impair central vision - they will still be able to navigate their environment

• Explain that it is possible to develop WET AMD at any stage of DRY AMD - make aware of sx of WET - sudden reduction in vision or metamorphopsia 

• Amsler chart for self-monitoring 

• Ask px to regularly compare vision in the LE and RE whilst looking at a regular straight line target

• Explain likely to be some deterioration in vision but isn’t a forgone conclusion - progression may be so slow 

• Make aware of modifiable RF - STOP SMOKING - will be beneficial even after AMD has been diagnosed

What are antioxidants?

• Antioxidants have a protective effect on retinal cells 

• Combat action of free radicals which are produced by oxidative damage associated with incidence of light on the photoreceptors

What role does diet play in the development of AMD?

• Macula has an abundant source of harmful free radicals - increases with AGE

• Macula contains lutein and zeaxanthin - known as carotenoids - have antioxidant properties - causes yellow pigment 

• This pigment absorbs harmful short wavelength(blue) which would otherwise damage the retina - can’t be produced by the body so must be extracted from our diet

• Leafy green vegetables - e.g spinach - good source of carotenoids - can also take supplements such as Viteyes

• Increasing the proportion of antioxidants enhances the retinas ability to withstand harmful effects of free radicals

• This may lead to the control of progression of AMD - does NOT delay or prevent onset of AMD

• Vitamin C, E, and the carotenoids + lutein/zeaxanthin

• Make px aware diet only plays a small role in the clinical procedure of AMD

What would you recommend to dispense AMD px?

UV protection coated lenses can reduce progression of AMD

Optometric Management of WET AMD

• Urgent referral to Ophthalmologist using the Wet AMD ‘fast track’ pathway - aim to be seen within 2/52

• Email the completed referral letter to a dedicated macula clinic - bypasses GP and reduces waiting time

• If unsure of whether Dry/Wet still use the fast track pathway

• If no fast track pathway available then same day phone call to HES

• Last resort be referred to A&E

Ophthalmological management of WET AMD

• Intravitreal injection of anti-VEGF agents - block action of VEGF - occur due to Ischaemia 

• Examples include; Ranibizumab (Lucentis), Bevacizumab (Avastin), Aflibercept (Eylea)