25th December 2023

Macula disease

Age-related macular degeneration (AMD)

AMD is a leading cause of irreversible blindness worldwide. AMD reflects a complex interaction between genes and environmental factors, which have not yet been fully elucidated. The hallmark of AMD is drusen, which are yellow deposits that develop within the outer retina. Drusen disrupt the homeostasis of photoreceptor outer segments, causing a slow, gradual loss of vision. Drusen also predispose to breaks within the outer retina. New vessels may then grow from the choroidal circulation (choroidal new vessels) to the retina, leading to neovascular disease. Choroidal neovascularisation predisposes to macula bleeding, oedema and potentially rapid reduction of vision.

Classification:

Traditionally, two forms of AMD are described: ‘dry’ AMD, characterised by drusen and ‘wet’ AMD by the presence of CNV and retinal haemorrhages. More recently, AMD is now recognised as a spectrum of disease ranging from early and intermediate AMD (drusen and altered RPE) to late AMD (neovascularisation; exudative disease).

Risk Factors:

• Age: most patients are above 60. If below 50 years of age, a secondary cause for choroidal neovascularisation must be sought
• Family history
• Smoking
• Caucasian
• Female
• High cumulative sunlight exposure
• Obesity
• Hypercholesterolaemia

Clinical Presentation:

• Decreased VA: May be sudden reduction in vision with a central scotoma if there has been break-through bleeding from CNV
• Blurred or distorted vision (metamorphopsia)
• Sudden visual loss: Break-through bleeding from CNV; patients often complain of a dense central scotoma
• Fundoscopy: drusen; pigmentary changes; retinal haemorrhages

Management:

There are no proven interventions for early or intermediate AMD. Patients should be advised to stop smoking. Vision should be monitored by an Amsler grid, which allows patients to detect new metamorphopsia. The Age-Related Eye Disease Study (AREDS) and AREDS2 studies investigated the role of high-dose vitamins on the progression of AMD. The results indicated that supplementation may slow the progression from intermediate to advanced disease. The original AREDS formulation contained vitamin C, vitamin E, beta-carotene, zinc oxide and cupric oxide. The AREDS2 formulation replaced beta-carotene with lutein, zeaxanthin and omega-3 fatty acids due to the possible increased risk of lung cancer in former smokers with beta-carotene. The formulation doses are in excess of recommended daily allowances, and no long-term data is available regarding adverse risks associated with excessive use. Decisions to initiate AMD supplements are best taken in conjunction with a medical retina specialist.

Treatment of neovascular AMD has been revolutionised by the introduction of anti-VEGF agents (ranibizumab; bevacizumab; aflibercept), which restore macula architecture, halt progression of neovascularisation and improve visual acuity in approximately 1/3ʳᵈ of patients.

Central serous chorioretinopathy (CSCR)

CSCR is an idiopathic macula disease characterised by the accumulation of subretinal fluid. It typically affects males between the ages of 25-50 and is associated with a ‘type A’ personality. Affected individuals may have a history of systemic or topical corticosteroid use.

Clinical features:

• Blurred/decreased vision
• Metamorphopsia
• Micropsia (minification of objects)
• Central scotoma

Examination usually detects a shallow serous detachment of the macula, best appreciated on slit-lamp examination. Management is usually conservative, with spontaneous resolution of 1-6 months. If persistent or recurrent disease, focal laser photocoagulation may be considered.

Image Source: Wikimedia Commons (2012). Intermediate age related macular degeneration, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Intermediate_age_related_macular_degeneration.jpg (Accessed on: 15  May 2022).

Image Source: Wikimedia Commons (2020). Amsler grid – distorted vision (metamorphopsia), Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Amsler_grid_-_distorted_vision_(metamorphopsia).png (Accessed on: 15  May 2022).