Blindness

May 31, 2020

5 min read

It can be easy to take something like your eyesight for granted. But across the world, millions of people are currently living with low or impaired vision. According to the World Health Organization, about 285 million people are visually impaired, and as many as 39 millions of them are blind.

The vast majority (about 82 percent) of all people who are blind are older than 50. However, blindness and other vision problems can ocur at any point within a lifetime. Keep reading to learn about the most common causes.

Common Causes of Blindness

Blindness simply means the inability to see because of injury, disease, or a congenital condition. Some organizations, including the National Federation of the Blind, define blindness as any condition that causes eyesight to be is bad enough, even with corrective lenses, that a person must use alternative ways to participate in activities that people with normal vision are able to do. "Legal blindness" means that a person has visual acuity of 20/200 in their eyes, even with correction (like glasses or contacts). This means that a person who is legally blind can see from 20 feet away what a person with 20/20 vision can see from 200 feet away.

Complete or partial blindness can occur due to a variety of reasons. Here are the leading causes:

Optic nerve hypoplasia (ONH)

This condition is caused by underdevelopment of optic nerves, the bundles of fibers that transmit visual information from the eyes to the parts of the brain that process vision. About 1 in 10,000 children are born with ONH.

Glaucoma

This is a group of eye conditions that cause progressive damage to the optic nerve. Glaucoma typically happens when the inner eye pressure begins to rise, but the condition can also occur even if the inner eye pressure is normal. It's more common in older people, but it can occur in infants and young children, too.

There are two main types of glaucoma: open-angle glaucoma is the most common. Progressive tunnel vision (loss of peripheral vision) is a common sign, although the condition can develop for years before showing noticeable signs or symptoms. The other type of glaucoma is known as angle-closure glaucoma—this is considered a medical emergency and includes symptoms like sudden blindness, headache, and eye pain.

Cataracts

By age 80, nearly half of all people have at least one cataract, which is a clouding and discoloration of the lens inside the eye. Blindness can occur if the cataract becomes large enough. This type of vision loss may be reversible with cataract replacement surgery.

Signs of cataract include cloudy or blurry vision, the appearance of halos around bright lights, and fading color vision. Children can get cataracts, too.

Eye injury

Irreversible damage to the eye that may lead to blindness include chemical burns, ultraviolet radiation damage ("snow blindness" or "eye sunburn," also called photokeratitis), blunt force trauma, pokes and jabs, and foreign object impalement. Severe infections of the eye may also lead to permanent damage that can threaten vision.

Two types of AMD exist. Wet AMD occurs when small abnormal blood vessels grow behind the retina (light-sensitive tissue inside the eye). These blood vessels leak fluids, which damages the retina and center of the retina, an area called the macula. Dry AMD occurs when the macula and retinal tissue thin and degrades overtime. This type of AMD is far more common and is associated, though not necessarily caused by, the presence of small yellow and white growths beneath the retina called drusen.

People with AMD typically notice a loss of central vision first, with their peripheral (side) vision remaining intact. Total blindness can develop if the condition progresses to advanced stages.

Diabetic retinopathy

Most people with diabetes develop some degree of vision loss, and about 1 in 5 people already have diabetic retinopathy when they get their initial diagnosis of diabetes. Diabetic retinopathy occurs when blood vessels behind and around the retinas become damaged, leading to deterioration of the retinal tissue. This is driven by high and uncontrolled blood sugar. Having diabetes also increases a person's risk of other eye conditions like glaucoma and cataracts.

Diabetic retinopathy often first presents with the appearance of "floaters" or dark spots in the visual field.

Cerebral or cortical impairment

This is vision loss and blindness caused by damage to parts of the brain that control vision, even though the eyes themselves may be working properly. It can happen due to conditions such as stroke, traumatic brain injury, brain tumors, and infections in the brain (like meningitis).

Retinitis pigmentosa

This is a group of genetic disorders which lead to breakdown and loss of cells in the retinas. Retinitis pigmentosa affects an estimated 1 in 4,000 people in the United States and Europe, and genetic mutations in at least 60 genes have been identified as underlying causes.

Other health conditions

Other health conditions, including cerebral palsy and Down syndrome, are frequently associated with vision impairments such as cataracts and glaucoma. Being diagnosed with one of these conditions may increase a person's risk of becoming partially or fully blind.

It may not always be possible to prevent vision loss. But with early treatment and management, it can be possible to slow the progression of the underlying disease process. Early diagnosis is also important for implementing helpful strategies to compensate for vision loss, such as tactile reading and writing tools (e.g., Braille), walking canes or sticks, guide dogs, and audio tools.

It's totally possible to maintain a fulfilling and active lifstyle after becoming blind. If you or a loved one has a visual impairment, we want to hear about your story. What's helped? What challenges have you faced and overcome? Connect with others like you at Healthread, and be sure to check out these additional resources:

The American Council of the Blind

National Federation of the Blind

The American Academy of Ophthalmology (they offer tons of interesting resources on their website, including links to audiobooks and large print reading materials)