Blindness

What is blindness?

Blindness is the inability to see or a lack of vision. In the most severe cases, there’s an inability to see even light. It also means that you can’t correct your vision with eyeglasses, contact lenses, eye drops or other medical therapy, or surgery. Sudden vision loss is an emergency. It’s important to seek immediate medical help.

Types of blindness

• Partial blindness: You still have some vision. People often call this "low vision."
• Complete blindness: You can't see or detect light. This condition is very rare.
• Congenital blindness: This refers to poor vision that you are born with. The causes include inherited eye and retinal conditions and non-inherited birth defects.
• Legal blindness: This is when the central vision is 20/200 in your best-seeing eye even when corrected with glass or contact lenses. Having 20/200 vision means that you have to be 10x closer or an object has to be 10x larger in order to see compared to a person with 20/20 vision. In addition, you can be legally blind if your field of vision or peripheral vision is severely reduced (less than 20 degrees).
• Nutritional blindness: This term describes vision loss from vitamin A deficiency. If the vitamin A deficiency continues, damage to the front surface of the eye (xerophthalmia) This type of blindness can also make it more difficult to see at night or in dim light due to retinal cells not functioning as well.

You might wonder about color blindness, which is not blindness in the traditional sense. Another name for this issue is color deficiency. You perceive colors in a different way. You can inherit this condition or acquire it because of disease or damage that occurs in your retina or optic nerve. If you can only see black, white or shades of gray, you have achromatopsia.

You may also hear about preventable blindness or avoidable blindness. These terms refer to blindness that happens to people that have a diseases that is treatable but they never receive care. This often happens because of a lack of access to eye care or healthcare. For instance, people who never receive care for diabetes may develop diabetes-related retinopathy. People who don’t receive care for hypertension may develop hypertensive retinopathy.

How common is blindness?

Blindness is common throughout the world and in the U.S. It can happen to anyone.

In the U.S., about 1 million people are blind. Experts expect this number to double by 2050. There are many more people with low vision. Around the world, an estimated 43 million people are living with blindness.

What are the symptoms of blindness?

With complete blindness there is a lack of vision and the inability of the eye to detect light.

Symptoms that you may have while vision loss develops include:

• Blurry vision.
• Eye pain.
• Floaters and flashers.
• Sensitivity to light (photophobia).
• Sudden loss of vision, or the sudden appearance of black spots in your vision.

What causes blindness?

There are many causes of blindness, including injuries, infections and medical conditions.

Eye injuries and blindness

Eye injuries, or ocular trauma, can happen in many ways. It usually affects only one eye. Damage can result from:

• Chemical burns.
• Exposure to toxins
• Fights.
• Fireworks.
• Industrial accidents, including falls.
• Motor vehicle crashes.
• Sports.

Infections and blindness

Many infectious diseases can lead to vision loss and sometimes blindness. These include:

• Trachoma. This is the leading cause of preventable blindness in the world.
• Cytomegalovirus.
• Endophthalmitis.
• Histoplasmosis.
• Keratitis, including acanthamoeba keratitis.
• Rubella.
• Shingles.
• Syphilis.
• Toxoplasmosis.
• Uveitis.

Non-infectious diseases and blindness

Many non-infectious diseases can cause blindness, but some in only the most severe stages of the disease. These include:

• Retinitis pigmentosa. This term refers to a group of conditions that affect your retina, the part of your eye that has special cells that react to light. As the condition progresses, the retinal cells break down. This leads first to problems seeing at night and then subsequent loss of your peripheral vision.
• Age-related macular degeneration. This condition affects the macula, the part of your retina that controls central vision. When substantial central vision loss occurs, tasks like reading or recognizing people’s faces become very difficult, but your peripheral vision often remains intact.
• Retinopathy of prematurity. This retinal condition happens to some premature babies. Blood vessels grow into parts of their eye where they don’t belong. Scar tissue forms and can damage their retina, leading to significant vision loss and blindness.
• Cataracts. Cataracts cause vision loss by clouding the lenses of your eyes, leading a blurring of the vision and loss of contrast. Without access to surgical care, advanced cataracts can lead to blindness.
• Diabetes-related retinopathy. This condition may happen when you have diabetes and the blood vessels in the eye are damaged. The vision loss may be mild at first, but with progression or lack of treatment, blindness can occur.
• Glaucoma. With this condition, you have optic nerve damage. The vision loss often starts in the periphery but can lead to blindness in advanced stages of the disease.
• Leber hereditary optic neuropathy. This term refers to an inherited type of gradual vision loss. For unknown reasons, it affects males more than females.
• Anophthalmia. This disease happens when you’re born without one or both eyes.
• Microphthalmos. This disease happens when you’re born with very small eyes. Sometimes these smaller eyes don’t work as well as they should, or at all.
• Stroke. You can lose your eyesight from a stroke that occurs in an area of the brain that is involved in seeing, like the occipital lobe or along the visual tract. The stroke reduces or blocks blood flow to your brain.
• Cancer. Cancers, like retinoblastoma or orbital tumors, can cause eyes to become blind.
• Nutritional deficiencies. A poor diet can cause vision loss. Vitamin A deficiency is one cause, but you also need B vitamins and other minerals and vitamins for healthy vision.

How is blindness diagnosed?

A provider will test each eye for sight, giving you a thorough eye exam. It’s possible for blindness to affect only one eye.

Tests may include:

• The Snellen test: You’re probably familiar with this test. A provider asks you to read lines of letters that get smaller as they go down the page. This test of visual acuity measures what you can see in front of you (central vision).
• Visual field testing: The visual field means more than central vision. It’s what you can see to either side or above and below without moving your eye.

How is blindness treated?

The type of treatment available depends on your condition. Providers can treat some forms of blindness with medications or glasses but can’t treat other types, such as the ones where your eyes are missing or completely damaged. In these cases, your provider may recommend visual rehabilitation. The goal of vision rehabilitation is to enhance visual functioning so you can meet your visual goals and improve your quality of life. Often, this happens through low-vision training, therapy and using low-vision devices.

Treatment for various forms of blindness

Treatment exists for some forms of blindness, depending on the cause and how extensive the eye damage is.

• Medication: Anti-infective drugs treat some forms of blindness caused by infections.
• Cataract surgery: Surgery can treat cataracts successfully in most cases.
• Corneal transplant: A provider may be able to replace your scarred cornea.
• Retinal surgery: A provider may be able to repair damaged retinal tissue with surgery and/or a laser.
• Vitamin supplements: You may be able to reverse the vision loss of xerophthalmia by taking vitamin A. You may need vitamin B or vitamin D supplements to treat vision loss caused by a poor diet.

How can I reduce my risk of developing blindness?

You can’t prevent some types of blindness. But blindness is preventable in many cases.

Some governments and societies are working to stop blindness caused by preventable diseases, like trachoma. They’re making medicines more available in large areas of the world.

On a personal level, there are things you can do to reduce your risk of partial or total blindness. These include:

• Have regularly scheduled eye exams. Follow the advice of healthcare providers on how often you should go for exams. Always contact an eye care provider when you have a change in vision or something wrong with your eyes. Wear your prescription glasses and contact lenses when necessary.
• Keep blood sugar levels stable if you’re a person with diabetes and manage your blood pressure if you have high blood pressure.
• Wear protective gear when you’re working, riding a motorcycle or participating in contact sports. Don’t forget to wear sunglasses.
• Eat foods that make up a healthy, well-rounded diet.
• Get enough exercise. Ask your provider about an exercise plan that’s healthy for you.
• Achieve a healthy weight for you.
• Know about health issues in your family.
• Quit smoking, or never start.
• Avoid infections in your eye by always washing your hands when you put your contacts in and following instructions about how often to change them.

What can I expect if I have blindness?

If you’re completely or partially blind, there are options. It may help to learn as much as you can about your condition.

Living with blindness affects your life and the lives of your family and friends. It affects your mobility, your ability to care for yourself or others, your employment – it even affects how you relax and have fun. Some of these issues may be even more pressing for older adults.

Ask your ophthalmologist about ways of coping with low or no vision or recommendations for services that can help you. These services can include:

• Education.
• Emotional health.
• Skills training.
• Technology training.
• Recreational options.

When should I see a healthcare provider about vision issues?

Get immediate medical help if you:

• Lose vision suddenly.
• Have pain in your eye.
• Have some type of accident that affects your vision.
• Have flashes or new floaters in your vision.

What questions should I ask my provider?

You probably have many questions for your provider. They may include:

• Can you treat this type of blindness?
• Am I eligible to participate in clinical trials?
• If you can’t treat this type of blindness, what kinds of services will I need?
• Can you recommend a support group?

A note from Cleveland Clinic

Hearing a diagnosis of blindness may bring on many emotions because of the inevitable impact on your life. It’s important and practical to get whatever support you need. Members of your healthcare team are there to answer questions and help to provide tools to make sure you have the best quality of life.