Investigations
1st investigations to order
Amsler grid
Test
Useful for determining subjective changes in central (macular) visual field.
Distortion (metamorphopsia) may represent active areas of macular exudation.
Dark areas (scotomas) may represent atrophic areas of the macula.
Result
focal area of distortion
optical coherence tomography
Test
Definitive test for confirming the presence of subretinal and intraretinal fluid.
Recommended if clinical examination and/or fluorescein angiography shows evidence for choroidal neovascularisation (CNV) and leakage.
Used to monitor changes in the volume of intraretinal and subretinal fluid before initiating treatment for CNV.
Can be used to confirm the presence of a hyper-reflective (fibrovascular) scar.
Result
intraretinal fluid; subretinal fluid; pigment epithelial detachment; loss of normal retinal pigment epithelium and photoreceptor architecture; subretinal hyper-reflective material, hyper-reflective scar
optical coherence tomography angiography
Test
An increasingly available option on optical coherence tomography machines. May be used to demonstrate choroidal neovascularisation (CNV). The technology is developing to overcome limitations related to artefacts.
Result
CNV in subretinal or subretinal pigment epithelium space. Watch for artefacts.
Investigations to consider
fluorescein angiography
Test
Ordered if history and/or clinical examination or optical coherence tomography suggests choroidal neovascularisation (CNV), and is the definitive test for the confirmation of CNV and active leakage.
May be used to measure the distance of CNV from the centre of the fovea. Result aids in determining treatment.
Can be used to confirm the presence of drusen (autofluorescence), geographic atrophy (transmission defects), and CNV (expanding hyperfluorescence).
Can be used to distinguish between classic and occult CNV. Classic CNV presents with early well-defined hyperfluorescence with margins blurring in later stages of the angiogram due to leakage, whereas occult CNV exhibits late 'stippled' or diffuse hyperfluorescence.
Can be used to rule out the presence of active CNV, unless the CNV is old and inactive or blocked by haemorrhage.
Result
autofluorescence; transmission defects; areas of expanding hyperfluorescence; focal areas of staining
indocyanine green angiography
Test
Allows a better visualisation of the deeper choroidal vessels. It may be helpful in situations where the source of leakage is obscured by a haemorrhage of the retina, which makes interpretation of fluorescein studies difficult.
It can also be helpful to identify features of idiopathic polypoidal choroidal vasculopathy and in identifying a form of neovascularisation in AMD called a RAP (retinal angiomatous proliferation) lesion.[31]
Result
hyperfluorescence; may show areas of dye leakage
autofluorescence imaging
Test
Useful for delineating areas of geographic atrophy in dry AMD. Can also be used to detect reticular pseudodrusen.
Result
areas of hypo-autofluorescence/absence of autofluorescence delineate areas of geographic atrophy; reticular pseudodrusen appear as spots of reduced autofluorescence
Emerging tests
genotyping
Test
Useful only for research purposes.
May be helpful in prognostic identification.
Result
genetic factors that predispose to AMD
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