Age-related macular degeneration
Updated: Nov 16, 2022
Age-related macular degeneration (ARMD) is an acquired degenerative disorder affecting the macula, with the hallmark being the presence of ‘drusen’ in the macula. There are two main subtypes, which we will describe in the following article.
ARMD is usually classified into two types: Dry ARMD (non-exudative, non-neovascular), and Wet ARMD (exudative, neovascular). The former makes up 90% of cases, whilst the latter is less common, however is associated with rapid progression to advanced vision loss. Another, temporal classification of the condition exists, where the disease is classified as ‘early’, ‘intermediate’, or ‘advanced’ ARMD.
A combination of genetic and environmental risk factors are thought to interact to modify the Bruch's membrane/choroid complex, the retinal pigment epithelium (RPE) and photoreceptor cells. Drusen, the main histopathological hallmark of the condition, are extracellular eosinophilic deposits located between the RPE and Bruch’s membrane, thought to be derived from immune-mediated and metabolic processes in the RPE. Age-related drusen are common after the 6th decade, but these are biochemically distinct from the drusen we see in ARMD.
Age is the biggest risk factor
Family history: two polymorphisms on chromosome 10q26, Tyr402His (Complement factor H locus, CFH) and Ala69Ser (ARMS2) may be responsible for up to 50-75% of the genetic risk. The former helps to protect cells from complement-mediated damage.
Smoking doubles the risk
High fat intake and obesity
Aspirin may increase the risk of neovascular disease (but limited evidence!
💡 ARMD is the most common cause of irreversible vision loss in the developed world.
In the UK, significant visual impairment (binocularly 6/18 or worse) from AMD affects about 4% of the population aged over 75 years and 14% of those over 90.
Dry Age-Related Macular Degeneration
Dry ARMD is also known as non-exudative, or non-neovascular ARMD. Vision declines over a period of months/years, usually in both eyes, however they may be asymmetrically affected. The main clinical sign is soft drusen. With progression, the end result of dry ARMD is geographic atrophy (GA): well circumscribed areas of RPE atrophy, with variable loss of the retina and choriocapillaris. OCT may show drusen: in addition to loss of RPE in geographic atrophy.
Wet Age-Related Macular Degeneration
Wet ARMD, also known as exudative or neovascular ARMD, is differentiated from early or dry ARMD by the presence of choroidal neovascularization (CNV), where new blood vessels from the choroid penetrate through the Bruch membrane and proliferate either between Bruch’s membrane and the RPE or in the subretinal space. Around 10% of cases of dry ARMD will ultimately lead to the development of CNV. With progression, the end result of wet ARMD is disciform macular degeneration.
CNV (choroidal neovascularisation) and PED (pigment epithelial detachment, where the pigment epithelium detaches from the inner collagenous layer of the Bruch membrane) are two of the main manifestations of neovascular ARMD, however two other conditions, retinal angiomatous proliferation (RAP) and polypoidal choroidal vasculopathy (PCV), have also been included under the umbrella of neovascular AMD.
Only drupelets (drusen <63nm) No AMD pigmentary abnormalities
Medium drusen (>63 μm but <125 μm)
No AMD pigmentary abnormalities
Large drusen (>125 μm) Any AMD pigmentary
Neovascular AMD and/or any geographic atrophy
Pigmentary abnormalities refers to hyper- or hypopigmentary abnormalities associated with medium/large drusen and not due to other known disease.
Gradual vision loss
Visual distortion, also known as metamorphopsia
Central scotoma of sudden onset
Pigment epithelial detachment
Cystoid macular oedema
OCT (Ocular Coherence Tomography)
OCT is a non invasive means of providing a cross-sectional image of the posterior segment, and is particularly helpful in monitoring disease progression as well as response to treatment in ARMD.
FFA (Fundus fluorescein angiography)
Useful if there is suspicion of exudative ARMD. This can demonstrate hypofluorescent and hyperfluorescent changes. Most lesions are hyperfluoerecent, (e.g. drusen, RPE atrophy, choroidal neovascular membranes, subretinal fibrosis) rather than hypofluorescent (haemorrhage, lipid exudation, and pigment hyperplasia). FFA also helps distinguish CNV patterns, with a ‘classic’ pattern showing leakage infront of the RPE, and an ‘occult’ lesion being sub-RPE.
AREDS2 (The Age Related Eye Disease Study 2) suggested a regimen of vitamin E, vitamin C, lutein, zeaxanthin, zinc and copper may reduce the risk of development to advanced ARMD in individuals with certain features of dry ARMD.
Modifying risk factors: a diet of green leafy vegetables, smoking cessation
Amsler grid testing: should be provided for home use, with instructions to regularly self test and to seek urgent advice in the event of any change (distortion on the grid is a sign of metamorphopsia and potential development to exudative ARMD).
Treatment with intravitreal injection of anti-VEGF agents: these work to slow and reverse the growth of new vessels.
NICE guidelines suggest first line treatment is Ranibizumab (Lucentis®) - this is often a monthly injection
Bevacizumab (Avastin®) is currently unlicensed in the UK however is commonly used as it is a cost effective regime
NICE guidelines suggest that ranibizumab, within its marketing authorisation, is recommended as an option for the treatment of wet age-related macular degeneration if all of the following apply:
The best-corrected visual acuity is between 6/12 and 6/96
There is no permanent structural damage to the central fovea
The lesion size is less than or equal to 12 disc areas in greatest linear dimension
There is evidence of recent presumed disease progression (blood vessel growth, as indicated by fluorescein angiography, or recent visual acuity changes)
Bowling, Brad. Kanski’s Clinical Ophthalmology: A Systematic Approach . 2016. Open WorldCat, http://public.ebookcentral.proquest.com/choice/publicfullrecord.aspx?p=2029294.
Hobbs, Samuel D., and Kristine Pierce. ‘Wet Age-Related Macular Degeneration (Wet AMD)’. StatPearls, StatPearls Publishing, 2022. PubMed, http://www.ncbi.nlm.nih.gov/books/NBK572147/.
Ratnapriya, R., and E. Y. Chew. ‘Age-Related Macular Degeneration – Clinical Review and Genetics Update’. Clinical Genetics, vol. 84, no. 2, Aug. 2013, pp. 160–66. PubMed Central, https://doi.org/10.1111/cge.12206.
Batioglu, Figen, et al. ‘Short-Term Outcomes of Switching Anti-VEGF Agents in Eyes with Treatment-Resistant Wet AMD’. BMC Ophthalmology, vol. 15, Apr. 2015, p. 40. PubMed Central, https://doi.org/10.1186/s12886-015-0025-z.
Recommendations | Age-Related Macular Degeneration | Guidance | NICE https://www.nice.org.uk/guidance/ng82/chapter/Recommendations#pharmacological-management-of-amd. Accessed 10 Oct. 2022