What Causes Blindness?

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 halos around light sources

• decreased vision

• watery eyes or eye draining

• eye redness

• double vision

• lines look wavy or distorted

• blind spots in the center of your field of vision

• often seeing changes in your vision quality

• losing peripheral vision

• intense eye pain

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

1. Macular degeneration

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, AMD can slowly damage your central vision.

AMD occurs when cells in the center of your retina (macula) become damaged over time. There are two types of AMD: 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 ethnicities.

2. Glaucoma

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 progresses 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

3. Cataracts

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

Cataracts are a common, vision-threatening eye condition. The National Eye Institute estimates that by the age of 80, half of all adults in the United States will have cataracts 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

4. Diabetic retinopathy

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.

5. Amblyopia

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:

• family history of:

  • amblyopia

  • cataracts

  • other eye conditions

• low birth weight or premature birth

• developmental disabilities

6. Strabismus

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.

The causes of strabismus, such as refractive error or crania nerve palsy, are well-known, but risk factors but risk factors include:

• family history of strabismus

• having other eye conditions

• eye or brain injury

• having Down syndrome or cerebral palsy

Other causes

Other common causes of blindness are uncorrected refractive errors and diabetic retinopathy. In fact, uncorrected refractive error is one of the most common causes.

Some more uncommon causes include:

• eye injures

• brain injuries

• eye surgery complications

• genetic disorders

• trachoma, or a chlamydia infection in your eye

• tumors

• stroke

• retinal detachment

• severe eye infections

• retinitis pigmentosa (RP)

How can I prevent blindness?

Getting a regular dilated eye exam is one of the best ways to prevent vision loss. These eye exams can also help you catch a condition early when 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

• avoiding smoking, or trying a smoking cessation program

Frequently asked questions

What is the number one cause of blindness?

According to the Centers for Disease Control, age-related eye diseases are the leading causes of blindness. Cataracts are the top cause of blindness worldwide and vision loss in the United States.

Diabetes is also responsible for 90 percent of blindness in U.S. adults.

What diseases cause blindness in young adults?

The leading causes of vision loss in U.S. adults between 19–40 years of age are eye injuries and visual stress.

What are the most common causes of blindness in children?

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

• retinopathy of prematurity

• nystagmus

• cataracts

• optic nerve atrophy

What degree of blindness is considered a disability?

Legal blindness occurs when one cannot correct vision above 20/200 in the better eye. That means one needs 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.

The takeaway

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.