28 HOW TO TREAT : AGE-RELATED MACULAR DEGENERATION
28 HOW TO TREAT : AGE-RELATED MACULAR DEGENERATION
14 JULY 2023 ausdoc . com . au
Hispanic heritage ( 0.16 %; 0.05-0.46 ). Between geographical regions , cases of AMD are less prevalent in Asia than in Europe and North America ( early : 6.3 % vs 14.3 % and 12.8 %; any : 6.9 % vs 18.3 % and 14.3 %). 10
No significant impact of gender has been noted on prevalence of AMD . 11
In an Australian setting , the Melbourne Visual Impairment Project and Blue Mountains Eye Study in the 1990s reported the prevalence of late AMD as 0.68 % and 1.9 %, respectively . A more recent 2017 population-based study reported the prevalence of late AMD in non-Indigenous Australians as 0.96 % and 0.17 % in Indigenous Australians . 12
PATHOGENESIS
AMD affects the central portion of the retina that is responsible for high-acuity vision . The retinal pigment epithelium ( RPE ) is responsible for removing metabolic wastes through the Bruch ’ s membrane into the choroidal vasculature . However , with age , this process is interrupted , leading to accumulation of material , known as drusen : yellow deposits of acellular debris found between the RPE and Bruch ’ s membrane . Late-stage AMD results in either cell death ( atrophic AMD ) or growth of new vessels through Bruch ’ s membrane that can leak and bleed ( neovascular AMD ).
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The presence and size of drusen are key components when grading the stage of AMD . According to the Beckman classification , early AMD is defined by the presence of medium drusen ( 63-125 µ m in diameter ) and intermediate AMD is defined by the presence of large drusen ( greater than 125 µ m in diameter ) and / or definite RPE pigmentary abnormalities . Late AMD is defined as either neovascular or atrophic AMD . 12
By assigning a risk score of 1 for each risk factor in each eye ( large drusen or pigmentary change ), one can achieve a total maximum risk score of 2 per eye or 4 per patient . Thus , a five-step severity scale of 0 ( no risk factors ) to 4 ( both risk factors in both eyes ) has been established . The five-year risk of late AMD developing increases by a factor of 100 between a score of 0 and 4 . There is a low risk of five-year progression to late AMD for scores of 0 and 1 and a doubling of risk between a score of 2 and 3 and a score of 3 and 4 ( 12 %, 25 % and 50 %, respectively ). 12
CLINICAL SYMPTOMS
Symptomatic
MACULA disease is characterised by distortion of straight lines , as well as images sometimes appearing smaller ( micropsia ) or larger ( macropsia ). Patients can report a central blur or reduced vision . Reading vision is typically more affected than distance vision .
A sudden onset or worsening of distortion in one eye is more suggestive of wet ( neovascular ) AMD . This is the basis of home monitoring , testing one eye at a time with an Amsler grid ( see figure 2 ). Difficulty reading in dim light and taking a long time to recover from bright lights are also potential symptoms of macula disease .
Asymptomatic
Patients with neovascular AMD can be asymptomatic in the early stages . Involvement of the second eye is often identified on optical PAGE 30
Figure 1 . Location of key landmarks in the central retina . A . Optic nerve head . B . Foveal centre . The white circle outlines the macula .
Figure 2 . Example of normal vision on an Amsler grid ( left ) and central blur and distorted vision with macula disease ( right ).
A B
Figure 3 . Example of OCTA .
Figure 3A . OCTA in a patient newly diagnosed with wet ( neovascular ) AMD .
Figure 3B . OCTA in a normal patient .