Blindness is usually due to age-related conditions such as macular degeneration, glaucoma, or cataracts. But other rare conditions can also cause blindness in people of all ages.

More than 4 million adults in the United States above the age of 40 years had low vision or were legally blind in 2022. Experts expect that number to double by 2050 as the population ages.

While vision loss is usually age-related, other factors can also play a role. Read on to learn about seven of the most common causes of blindness, their risk factors, and how to reduce your risk.

How do I know if I’m going blind?

Signs of vision loss and blindness can be subtle and increase over time or can appear suddenly. Contact an eye doctor right away if you notice any of the following symptoms:

  • seeing flashes of light
  • seeing floaters or specks
  • seeing haloes around light sources
  • decreased vision
  • watery eyes or eye draining
  • eye redness
  • double vision
  • lines look wavy or distorted
  • empty areas in the center of your field of vision
  • often seeing changes in your vision quality
  • losing peripheral vision
  • intense eye pain
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If you’re older than 60 years, it helps to be aware of age-related macular degeneration (AMD). It’s the most common cause of vision loss in people of this age group. While not painful, it can slowly damage your central vision.

AMD occurs when cells in the center of your retina (macula) get damaged over time. AMD has two types: wet and dry. Dry AMD is more common but less severe.

An early sign of wet AMD is straight lines appearing crooked. With dry AMD, you may first experience blurred or distorted central vision.

Risk factors for AMD include smoking or having a family history of the disease. White people may also be at a higher risk than other races.

Glaucoma is a group of diseases that can damage the optic nerve in the back of your eye. About half of all people with glaucoma don’t know they have it because it can progress very slowly. It first damages your side (peripheral) vision and can eventually cause blindness.

Researchers aren’t sure what causes glaucoma. It may be related to high eye pressure, but even people with regular eye pressure can develop it. Regular eye exams every 1–2 years can help doctors detect it early.

Risk factors for glaucoma include:

  • having a family history of glaucoma
  • being older than 60 years and Latino
  • being older than 40 years and Black

A cataract is the clouding of the lenses because of the proteins in one or both of your eyes. These proteins form a dense area, making it hard for your lens to send clear images to other parts of your eye.

Cataracts are a common, vision threatening eye conditions. The National Eye Institute estimates that by the age of 80 years, half of all adults in the United States will have cataract or cataract surgery in one or both eyes.

Risk factors for cataracts include:

  • aging
  • smoking (if you smoke)
  • alcohol (if you drink)
  • prolonged exposure to sunlight
  • diabetes

People with diabetes are at risk of developing diabetic retinopathy, including those with type 1 and type 2 or who are pregnant (gestational diabetes).

Frequent high blood sugar levels can damage blood vessels all over your body. It includes the tiny vessels in your retina, the area in the back of your eye that’s sensitive to light. The blood vessels can leak or grow unusually, causing vision loss and eventually blindness.

Retinitis pigmentosa (RP) is a rare group of inherited eye diseases. Genetic mutations that affect your retina can cause its cells to break down slowly.

While RP typically gets passed from parent to child at birth, injuries, infections, and some medications can cause damage to the retina that resembles RP.

Most people with RP eventually lose most of their sight.

Risk factors for RP include a family history of the condition or having other genetic disorders like Usher syndrome.

More commonly known as lazy eye, amblyopia typically affects just one eye. It usually starts in childhood, when your brain has trouble interpreting information from one of your eyes. Over time, the eye with better sight becomes stronger, while the eye affected by amblyopia becomes weaker.

Many parents don’t know their children have the condition until a doctor diagnoses it.

Risk factors for amblyopia include:

Ambylopia can often occur with strabismus or crossed eyes. Strabismus can also occur without amblyopia.

Muscles surround your eyes, allowing them to move and focus. When they don’t team together well, the sight in both eyes doesn’t align correctly. That can cause your brain to rely on one eye more than the other. It takes treatment to help them see together.

Researchers aren’t sure what causes strabismus, but risk factors include:

Less common causes of blindness include:

Regular dilated eye exams are one of the best ways to prevent vision loss. They can also help you catch a condition early when the treatment can be more effective.

You can also protect your vision by:

  • managing your blood sugar levels
  • eating a nutritious diet
  • maintaining a moderate weight
  • quitting smoking (if you smoke) or never starting smoking

Here are some answers to common questions about the causes of blindness.

What is the number one cause of blindness?

Cataracts are the top cause of blindness worldwide and vision loss in the United States.

What diseases cause blindness in young adults?

The leading causes of vision loss in U.S. adults under age 40 are refractive errors, accidental eye injuries, and diabetes.

What are the most common causes of blindness in children?

Children make up to 3% of people with blindness worldwide. The most common causes of blindness in children in the United States are:

What degree of blindness is considered a disability?

Legal blindness is when you cannot correct your vision above 20/200 in your better eye. That means you need to stand 20 feet away to see an object most people can see from 200 feet away. The Social Security Administration considers legal blindness a disability.

You have low vision when it’s less than 20/40 in the better-seeing eye, even when you have corrected vision.

Vision loss is becoming more common in the United States as the population ages. Age plays a significant role in the most common causes of vision loss, such as AMD, glaucoma, cataracts, and diabetic retinopathy.

But vision loss can happen to anyone at any age. Checking your sight with regular eye exams, healthy habits, and a knowledge of possible risk factors is essential for prevention and early diagnosis.