Age-related macular degeneration (AMD) is caused by a combination of aging, genetics, oxidative stress, and chronic inflammation that together damage the light-sensing cells at the center of your retina. About 8% of people in their early 50s already have some stage of AMD, and that number climbs to roughly 32% by the early 80s. No single factor is responsible. Instead, several biological processes overlap and reinforce each other over decades.
How the Retina Breaks Down Over Time
The retina depends on a thin layer of support cells called the retinal pigment epithelium, or RPE. These cells do an enormous amount of work: they feed the light-detecting photoreceptors above them, recycle visual pigments used in every moment of sight, and clear away cellular waste. The RPE consumes a lot of oxygen and processes a lot of fat-rich material, which generates high levels of reactive oxygen species, essentially aggressive molecules that can damage proteins and fats inside the cell.
When you’re young, your RPE cells handle this workload and clean up the damage efficiently. As you age, the cleanup systems slow down. Damaged proteins clump together with oxidized fats, forming a yellowish waste product called lipofuscin that builds up inside RPE cells. Lipofuscin interferes with the cell’s recycling machinery, making cleanup even harder. Meanwhile, waste products that the RPE can’t process get pushed outward and accumulate as small deposits called drusen between the RPE and the blood supply beneath it.
Drusen are a hallmark of early AMD. They’re not just inert clumps of debris. Once enough drusen accumulate, they act as inflammatory hotspots, attracting immune cells to the area and triggering a cycle of chronic, low-grade inflammation that accelerates damage to the RPE and, eventually, the photoreceptors it supports.
The Role of the Immune System
One of the strongest biological drivers of AMD is overactivation of part of the immune system called the complement system. This is a network of proteins that normally helps your body flag and destroy pathogens. In AMD, complement proteins activate excessively in the retina, generating inflammatory signals that recruit immune cells (macrophages, microglia, and mast cells) into the tissue surrounding the RPE.
These immune cells release enzymes that remodel and degrade the structural membrane beneath the RPE, called Bruch’s membrane. Mast cells, for instance, release enzymes that break down the surrounding tissue scaffold. Macrophages stimulated by complement signals release inflammatory molecules that further stress RPE cells. The result is a self-reinforcing loop: drusen trigger complement activation, complement activation recruits immune cells, immune cells cause tissue damage that produces more debris, and more debris feeds back into the cycle. Over time, RPE cells degenerate and can no longer support the photoreceptors, leading to the gradual central vision loss characteristic of dry AMD.
Genetics and Inherited Risk
Your genes play a major role in determining whether this process spirals out of control or stays manageable. Two genetic regions have the greatest impact on AMD risk: the complement factor H (CFH) gene and the ARMS2 gene.
CFH produces a protein that normally puts the brakes on complement activation. When you carry high-risk variants of CFH, that braking system is weaker, and complement-driven inflammation in the retina runs hotter than it should. People with two high-risk CFH variants are about 1.7 times more likely to develop the wet, advanced form of AMD compared to those with lower-risk versions. The CFH protein also helps protect RPE cells against oxidative stress directly, and AMD-associated variants reduce that protection.
ARMS2 risk variants carry an even stronger association. People with high-risk ARMS2 genotypes are roughly 2.8 times more likely to develop wet AMD and 1.7 times more likely to develop the advanced dry form called geographic atrophy. Having high-risk variants of both genes compounds the risk further. That said, carrying these variants doesn’t guarantee you’ll develop AMD. They raise your susceptibility, but the disease still depends on the accumulation of environmental and age-related damage over time.
What Triggers Wet AMD
Most AMD starts as the “dry” form, with drusen buildup and gradual RPE deterioration. In about 10 to 15% of cases, the disease progresses to “wet” AMD, which involves abnormal blood vessels growing up from the choroid (the blood vessel layer beneath the retina) into the retinal layers where they don’t belong. These new vessels are fragile and leak fluid or blood, causing rapid and severe vision loss.
The trigger appears to be vascular. As dry AMD worsens, blood flow through the choroidal vessels decreases. Research shows that the endothelial cells lining these vessels are lost even before RPE cells fail, suggesting that vascular damage may be one of the earliest events in the disease. Complement activation contributes to this vessel loss. As choroidal blood flow drops, the tissue becomes starved of oxygen. This oxygen deprivation sends out distress signals that stimulate the growth of new blood vessels, a process called neovascularization. Unfortunately, these emergency vessels are poorly formed and cause more harm than good.
Oxidative Stress and Why the Macula Is Vulnerable
The macula, the small central area of the retina responsible for sharp, detailed vision, is uniquely vulnerable to oxidative damage for several reasons. It has the highest concentration of photoreceptors, meaning its RPE cells process the most waste. It is bathed in high oxygen levels from the choroidal blood supply. It is exposed to focused light energy throughout your life. And it contains high concentrations of polyunsaturated fatty acids in photoreceptor membranes, which are especially prone to oxidation.
During the normal visual cycle, the conversion of light-sensitive pigments in photoreceptors generates reactive oxygen species as a byproduct. These molecules cause a chain reaction of fat oxidation in cell membranes. The RPE then has to phagocytize (essentially eat and digest) the damaged outer segments of photoreceptors daily. Over decades, this relentless cycle of light exposure, fat oxidation, and waste processing overwhelms the cell’s antioxidant defenses, particularly when those defenses are weakened by aging or genetics.
Smoking, Diet, and Other Modifiable Risks
Smoking is the single strongest modifiable risk factor for AMD. It dramatically increases oxidative stress throughout the body, reduces blood flow to the choroid, and promotes complement activation, hitting three of the main disease pathways at once.
Diet matters because the retina depends on specific antioxidant pigments, particularly lutein and zeaxanthin, to filter damaging blue light and neutralize free radicals. These pigments concentrate in the macula and form a protective layer. The landmark AREDS2 clinical trial, run by the National Eye Institute, found that a specific supplement formula slowed progression of intermediate AMD to advanced stages. That formula contains 500 mg of vitamin C, 400 IU of vitamin E, 10 mg of lutein, 2 mg of zeaxanthin, 80 mg of zinc, and 2 mg of copper (added to prevent zinc-related copper deficiency). These nutrients aren’t a cure, but they measurably reduce the odds of progression in people who already have intermediate disease.
Cardiovascular health also matters. High blood pressure, high cholesterol, and obesity have all been associated with increased AMD risk, likely because they impair choroidal blood flow and increase systemic inflammation.
Does Blue Light From Screens Cause AMD?
Lab studies show that intense blue light can damage retinal cells, and blue light does carry more energy than other visible wavelengths. However, there is currently no evidence that screens or LED lighting at normal domestic intensity levels are toxic to the human retina. Epidemiological studies looking at light exposure and AMD risk have produced conflicting results, and the link remains unproven. There is also no evidence that blue-light-blocking glasses or lens filters prevent AMD or slow its progression. Cumulative sunlight exposure over a lifetime is a more plausible concern than screen time, but even that relationship is debated.