Macular degeneration usually refers to age-related macular degeneration, commonly abbreviated AMD, a chronic disease affecting the macula, the specialised central region of the retina responsible for detailed, straight-ahead vision. The retina converts light into neural signals, and the macula contains a high concentration of photoreceptors needed for tasks such as reading, recognising faces, driving and distinguishing fine detail. AMD damages this central visual system while generally sparing peripheral vision, so it does not usually cause complete blindness. The National Eye Institute describes AMD as an age-associated condition that can blur central vision and is a leading cause of vision loss in older adults. The disease can affect one or both eyes, and the severity can differ between them.
There are two principal forms of AMD, known as dry and wet AMD. Dry AMD is the more common form and involves progressive changes and degeneration within the macula. It can be divided into early, intermediate and late stages, with late dry AMD including geographic atrophy, where important retinal cells are lost. Wet AMD, also called neovascular AMD, occurs when abnormal blood vessels grow beneath or within the retinal layers and leak fluid or blood, damaging the macula. Wet AMD is less common but can cause comparatively rapid central visual loss. Dry AMD and wet AMD are not entirely separate diseases; wet AMD can develop from pre-existing dry AMD. A person can also have different stages or forms affecting the two eyes.
Early AMD may produce no symptoms, which makes routine eye examinations important in people at risk. As disease progresses, central vision may become blurred or distorted, and straight lines can appear wavy or crooked. Reading may become difficult, faces may be harder to recognise, and tasks requiring fine detail can become increasingly challenging. In later disease, a blurred, empty or distorted area may develop near the centre of vision.
Peripheral vision is generally preserved, which means people may retain the ability to navigate using their side vision even when central detail is severely impaired. AMD is usually painless and does not normally cause an externally red or inflamed eye, helping distinguish it from conditions such as conjunctivitis and acute glaucoma.
The pathology of dry AMD includes the accumulation of deposits called drusen beneath the retina and progressive dysfunction or loss of retinal pigment epithelium and photoreceptor-related structures. Drusen can be detected during an eye examination and may occur before substantial visual symptoms. In advanced dry AMD, geographic atrophy represents loss of retinal cells in areas important for central vision.
The biological processes involve ageing, altered cellular metabolism, oxidative stress, inflammation, lipid handling and complement-related immune mechanisms, although no single mechanism explains every case. Recent research continues to investigate how deposits, inflammation, cellular energy metabolism and genetic susceptibility interact. Thus, AMD is not simply “wearing out” of the eye in a vague sense; it involves identifiable structural and molecular changes in the macular retina.
Wet AMD has a different immediate mechanism. Abnormal blood vessels develop beneath or around the macula in response to pathological signalling involving vascular endothelial growth factor and other pathways. These fragile vessels can leak fluid or blood into retinal tissues, disrupting the highly organised architecture needed for sharp vision. The leakage can produce rapid distortion and central visual loss.
Anti-VEGF medicines are therefore important treatments for many forms of wet AMD because they inhibit the vascular growth and leakage pathway driving the disease. Photodynamic therapy can also have a role in selected circumstances. Early recognition is particularly important in wet AMD because treatment can help prevent or reduce further loss, although existing retinal damage may not be completely reversible.
Diagnosis generally involves examination of the retina after pupil dilation and may include optical coherence tomography, commonly called OCT, which produces detailed cross-sectional images of retinal structures. Additional imaging can identify drusen, retinal fluid, bleeding and abnormal blood vessels. Amsler-grid testing may help detect changes in central vision between appointments, particularly distortion of straight lines, although it does not replace professional examination. Early disease can be discovered incidentally during routine eye examinations before a person notices symptoms. The distinction between dry and wet disease is clinically important because management differs substantially. An eye specialist may therefore use both the appearance of the retina and imaging findings to determine stage and activity.
Treatment depends on the stage and type. Early AMD may require observation and modification of risk factors rather than immediate drug treatment. For appropriate patients with intermediate or certain advanced forms, specific vitamin and mineral formulations based on the AREDS/AREDS2 research can reduce the risk of progression to advanced disease, although these supplements are not a universal treatment and should not be taken indiscriminately. Wet AMD can be treated with intravitreal anti-VEGF injections, which inhibit abnormal blood-vessel growth and leakage.
Photodynamic therapy has a more selective role. Late dry AMD has historically had fewer treatment options, although the therapeutic landscape continues to evolve, including treatments targeting complement pathways for selected geographic-atrophy patients in some healthcare systems. Low-vision rehabilitation and magnification technologies can also help preserve independence when central vision is impaired.
AMD differs from cataract and glaucoma in both location and visual pattern. Cataract affects the lens and commonly produces diffuse blur, glare and colour changes that can often be substantially improved by lens replacement. Glaucoma damages the optic nerve and typically begins with peripheral visual-field loss. AMD damages the macula and therefore predominantly affects detailed central vision. AMD also differs from ordinary presbyopia, which is an age-related focusing problem caused largely by reduced lens flexibility.
The term “macular degeneration” should not be interpreted as meaning that all macular disorders are AMD; diabetic macular disease, inherited retinal disorders, inflammatory disorders and other conditions can affect the macula through different mechanisms. Correct terminology is therefore important when interpreting visual symptoms or discussing prognosis.
