Age-Related Macular Degeneration

Age-related macular degeneration is a chronic, degenerative disease of the central retina (the macula) and a leading cause of irreversible central vision loss in older adults in high-income countries. It exists as a non-neovascular form, marked by drusen and, in advanced cases, geographic atrophy, and a neovascular form, in which abnormal new vessels grow beneath the retina and leak or bleed.

Definition

Age-related macular degeneration is a degenerative disorder of the macula and underlying retinal pigment epithelium and choroid, characterised early by drusen and pigmentary change, and progressing in advanced disease to either geographic atrophy (non-neovascular) or choroidal neovascularisation (neovascular), both of which impair central vision.

Scope

This entry covers the definition, pathophysiology, classification into non-neovascular (dry) and neovascular (wet) disease, epidemiology, and clinical relevance of age-related macular degeneration as a topic within retinal and vitreous disease. It treats the condition as a reference subject and does not provide diagnostic thresholds or treatment instructions.

Core questions

• What ageing and degenerative changes in the macula initiate the disease?
• How do the non-neovascular and neovascular forms differ in mechanism and visual consequence?
• Why does the disease selectively impair central rather than peripheral vision?
• Which genetic and environmental factors most strongly influence risk?

Key concepts

• Macula and central vision
• Drusen
• Retinal pigment epithelium
• Geographic atrophy
• Choroidal neovascularisation
• Non-neovascular (dry) versus neovascular (wet) disease
• Complement and inflammation in pathogenesis
• Vascular endothelial growth factor

Mechanisms

The disease begins with age-related dysfunction of the retinal pigment epithelium and the accumulation of extracellular deposits (drusen) between the epithelium and Bruch's membrane, accompanied by oxidative stress, impaired clearance of photoreceptor debris, and dysregulated complement-mediated inflammation. In the non-neovascular pathway, progressive loss of the retinal pigment epithelium and overlying photoreceptors produces geographic atrophy. In the neovascular pathway, angiogenic signalling, particularly via vascular endothelial growth factor, drives growth of choroidal new vessels through Bruch's membrane into and beneath the retina, where they leak fluid and blood and cause rapid central vision loss and eventual scarring (lim-2012; jager-2008; mitchell-2018).

Clinical relevance

Age-related macular degeneration is a major cause of low vision and blindness in ageing populations, and distinguishing its forms is central to ophthalmic care because they differ in course and prognosis. The condition illustrates the impact of a degenerative retinal disease on reading, driving, and independence. This entry is educational and descriptive and is not a basis for individual risk assessment or treatment decisions.

Epidemiology

A systematic review and meta-analysis estimated that age-related macular degeneration affected roughly 196 million people worldwide in 2020, with a projected rise to about 288 million by 2040, reflecting population ageing. Prevalence increases steeply with age, and established risk factors include increasing age, smoking, and genetic susceptibility, while the disease is a leading cause of blindness in older adults in high-income settings (wong-2014; mitchell-2018; lim-2012).

Evidence & guidelines

Knowledge of age-related macular degeneration draws on large epidemiological cohorts, genetic association studies implicating the complement pathway, and clinical trials establishing the role of anti-vascular-endothelial-growth-factor therapy in neovascular disease, as synthesised in major reviews. Specific clinical recommendations are issued by professional societies; this entry summarises the evidence base rather than reproducing them (mitchell-2018; jager-2008; lim-2012).

History

Macular degeneration was characterised clinically through fundus examination and, from the mid-twentieth century, fluorescein angiography, which allowed choroidal neovascularisation to be visualised. Early treatment relied on thermal laser and later photodynamic therapy for neovascular disease. The recognition of vascular endothelial growth factor as a driver of choroidal neovascularisation, together with advances in optical coherence tomography imaging, transformed management in the twenty-first century through anti-angiogenic pharmacotherapy (jager-2008; mitchell-2018).

Seminal works

• mitchell-2018
• jager-2008
• wong-2014

Frequently asked questions

What is the difference between dry and wet age-related macular degeneration?

Dry (non-neovascular) disease involves drusen and gradual degeneration of the macula that can progress to geographic atrophy, whereas wet (neovascular) disease involves abnormal new blood vessels growing from the choroid that leak fluid or blood and can cause more sudden central vision loss.

Does age-related macular degeneration cause total blindness?

It characteristically destroys central vision, affecting reading and fine detail, but typically spares peripheral vision, so affected people usually retain some navigational sight rather than complete blindness.