Blindness is a term that refers to both legal blindness and visual impairment.
It is estimated that 2.2 billion people worldwide suffer from some degree of blindness or visual impairment, and approximately half of these are due to preventable or treatable causes.
What Is Blindness?
The definition of blindness is vision that is so poor in both eyes that it interferes with activities of daily living despite attempted correction with glasses, contacts, or refractive surgery. Poor vision can result from damage to any part of the visual pathway, from the eyes to the nerves that transmit the images to the occipital lobe of the brain where vision is perceived and processed.
What Are the Various Types of Blindness?
The term blindness encompasses both visual impairment and legal blindness. Visual impairment means the best corrected vision (vision with glasses, contacts, or refractive surgery) is poor and results in difficulty functioning. Legal blindness is a specific term defined by the United States Social Security Administration to determine disability benefit eligibility. A person is deemed legally blind if the best corrected central visual acuity in the better-seeing eye is 20/200 or worse, or if the visual field is restricted to 20 degrees or less in the better-seeing eye.
What Causes Blindness?
Worldwide, the most common causes of visual impairment and blindness include unaddressed correction of refractive errors, cataracts, glaucoma, and corneal opacities from trachoma infection and injuries. In the United States and most other developed nations, the four most common causes of blindness are age-related macular degeneration, cataract, diabetic retinopathy, and glaucoma. Glaucoma is the leading cause of irreversible blindness in African Americans. Additional causes of blindness include inflammatory conditions like optic neuritis, inherited degenerations such as retinitis pigmentosa, retinopathy of prematurity (formerly called retrolental fibroplasia) seen in premature babies, vascular diseases, eye neoplasias such as retinoblastoma or optic glioma, and blocked blood vessels to the visual pathway due to strokes.
What Are Risk Factors for Blindness?
Worldwide, the leading risk factor for blindness is lack of access to health care resources to correct refractive errors and cataracts. Poor hygiene and lack of access to clean water plays a major role in the spread of trachoma, which in turn can cause visual impairment or even blindness.
The rising rate of obesity worldwide has led to marked increases in diabetes and diabetic retinopathy. Increasing life span has led to increased numbers of people with eye conditions that are naturally more prevalent with age, such as cataracts, glaucoma, and age-related macular degeneration.
A family history of eye disease is a risk factor. However, lifestyle choices and independent factors affect the incidence and severity of these inherited diseases. Smoking, obesity, and lack of access to health care can increase the risk of eye diseases progressing to blindness.
What Are Signs and Symptoms of Blindness?
Symptoms of poor visual acuity may range from trouble focusing to glare to difficulty perceiving light.
Markedly constricted visual fields are seen in conditions such as advanced glaucoma and pigmentary retinopathies. In these cases, despite a small central area of relatively clear vision, the surrounding severe peripheral vision loss results in tunnel vision that can be disabling.
People born with sight who later lose vision can still form images in their mind. However, in people who lose sight due to damage to the portions of the brain that process visual input, there can be a loss of ability to form images in the mind. This is the case with trauma or strokes affecting the occipital cortex of the brain.
Most blindness is unassociated with physical pain. However, angle-closure glaucoma and various infectious and inflammatory eye disease can cause both pain and severe visual loss.
In most cases of blindness, there are no outward signs evident to others. In some cases, however, a rhythmic back and forth motion of the eyes (nystagmus) occurs in some forms of congenital blindness (blindness from birth). When one eye has poor sight relative to the other, it may wander and be misaligned relative to the eye with good sight. This misalignment is called strabismus.
Is It Possible to Prevent Blindness?
Improved access to health care, clean water, and better hygiene are key factors for preventing blindness worldwide. Routine eye examinations are important to detect eye problems early, particularly for treatable conditions such as glaucoma.
Proper eye protection can prevent injuries from accidents, chemical burns, and sports injury.
Health habits also play a significant role in preventing blindness. Smoking, poor cardiac health, sedentary lifestyle, poor nutrition, and obesity are linked to more vision loss in diabetic retinopathy, glaucoma, and macular degeneration, so while these conditions may not be entirely preventable, the severity of vision loss can certainly be affected by lifestyle choices.
If you or someone you know is suffering these symptoms of blindness or has already lost portions of their vision, request an appointment with our offices today to see what treatment options are available.