According to a 2012 report from the World Health Organization, more than 39 million people in the world are blind.
If you factor in people with low vision, the number of people with a visual impairment soars above 200 million.
What causes blindness?
Blindness can be congenital or acquired later in life. The causes of blindness include:
The many causes of blindness can differ depending on the socioeconomic condition of the area.
In underdeveloped areas of the world, the principal cause of visual impairment is uncorrected refractive errors and cataracts. Refractive errors like myopia, hyperopia, and astigmatism are being left untreated and access to cataract surgery is often unavailable.
Infections, vitamin A deficiency, and injuries are also common causes of blindness in third-world nations.
In developed nations, the term blindness does not describe vision loss that can be corrected with glasses or contacts.
According to the Center for Disease Control (CDC), the leading causes of blindness in the United States are primarily age-related and include:
- Diabetic retinopathy
- Macular degeneration
What are some risk factors for blindness?
- Poor prenatal care
- premature birth
- advancing age
- poor nutrition
- failing to wear safety glasses when needed
- Poor hygiene
- A family history of blindness
- Presence of existing medical conditions like diabetes, hypertension, and cardiovascular disease.
What causes congenital blindness?
Congenital blindness is present at birth. Vision loss in infants can be either prenatal or postnatal. A prenatal onset of vision loss would occur at the time of conception or during the intrauterine period. Postnatal vision loss occurs during or after the birth of the child.
Prenatal Congenital Anomalies
Anophthalmos and microphthalmos are developmental abnormalities in which the entire eyeball is missing or small in size. These abnormalities may be caused by genes responsible for early eye development, however, the exact genes have not been identified. Environmental factors such as prenatal nutrition, radiation, and infections like rubella could also cause the underdevelopment of the eyes.
Colobomas are missing pieces of tissue in structures that form the eyes. Colobomas can appear as notches or gaps in the iris, retina, choroid, or optic nerve. Depending on the size and location of the coloboma, vision loss can be severe.
Infantile Glaucoma is believed to be an inherited condition that affects the drainage systems of the eye. If left untreated, increased pressure in the eyes can damage the optic nerve.
Retinal dystrophy is a deterioration of the retina that can cause loss of vision, night blindness, and light sensitivity. There are several types of retinal conditions and syndromes that are genetically inherited including, Leber’s congenital amaurosis, Knobloch syndrome, albinism, and achromatopsy.
Congenital cataracts occur when the natural lens of the eye is cloudy instead of clear at birth. Some syndromes and genetic disorders can cause congenital cataracts, but the cause is mostly unknown.
Retinoblastoma is the most common childhood malignancy. It is a rare cancer of the retina that is exclusively found in young children. If found early, retinoblastoma can be treated with chemotherapy, however, severe lesions may need enucleation (removal of the eye).
Perinatal and Postnatal Onset
Ophthalmia neonatorum occurs when the infants eyes are infected in the birth passage during delivery. It is a form of conjunctivitis transmitted by mothers who have contracted a sexually transmitted disease.
Premature infants are at risk for retinopathy of prematurity depending on birth weight, gestational age, and exposure to prolonged supplementary oxygen that was not properly controlled. Blood vessels in the retina of the eye can grow abnormally and cause bleeding and scarring on the retina.
Birth asphyxia and preterm birth can cause severe consequences like optic nerve lesions and cortical visual impairment.
What causes acquired blindness?
Unfortunately, losing vision is a common problem do to the process of aging, the development of a specific condition, or injury.
The leading causes of age-related vision loss are cataracts, glaucoma, macular degeneration, and diabetic retinopathy.
Cataracts occur when the natural lens of the eye becomes cloudy. Cataracts can occur in one or both eyes causing blurry vision, poor night vision, double vision, light sensitivity, and trouble seeing colors. Disease, injuries, genetics, and age are just a few reasons millions of people develop cataracts.
Glaucoma occurs when the fluid pressure inside the eyes rises and damages the optic nerves. Glaucoma is often called the “thief of sight,” because it slowly progresses over time without the person noticing until the disease is advanced.
Macular degeneration or age-related macular degeneration (AMD) affects the central part of the retina called the macula that allows us to see fine details and central vision. It is associated with aging and is the leading cause of blindness among people aged 65 years and older.
Diabetic retinopathy is a complication of diabetes that affects the blood vessels of the retina. According to the CDC, diabetic retinopathy is the leading cause of blindness in American adults.
Injuries such as abrasions, foreign objects, and lacerations to the eye can cause visual impairments. Trauma to the brain or eye region can also lead to blindness.
Sexually transmitted infections like chlamydia, gonorrhea, syphilis, herpes simplex, and hepatitis B can causes blindness if they go untreated. In addition, parasites will cause blindness too if they go undetected.
The signs and symptoms for any of these medical conditions are similar, so it is critical that you seek medical attention immediately if you suspect something is wrong with your eyesight. Quick diagnosis and treatment could prevent you from losing your vision.
How is visual impairment diagnosed?
A specialist, known as an ophthalmologist, is a medical doctor that deals with the diagnosis and medical treatment of eye conditions.
Several tests and procedures may be used to examine your eyes. Depending on the doctor and the number of tests required, a comprehensive eye exam can take an hour or more. All tests are important to fully evaluate vision and eye health.
Possible tests may include:
- Pressure readings to help diagnose and keep track of glaucoma.
- Corneal topography to look at the surface of the cornea for abrasions, swelling, or conditions like astigmatism.
- Dilated pupils to allow the doctor to look at the retina and optic nerves to check for signs of disease.
- Visual acuity testing to measure how well you see at near and far distances.
- Visual field test to determine if peripheral (side) vision is affected.
Can blindness be prevented or cured?
Blindness can be preventable with the proper education and access to medical care. Some visual impairments caused by injuries or nutritional deficiencies can be prevented with proper use of eye protection or through proper diet.
As the leading cause of blindness in American adults, diabetic retinopathy can be preventable with careful control of blood sugar levels, proper diet, and exercise.
In most cases, the most important preventable measure is through early detection and appropriate treatment.
The prognosis for visual impairment depends on the cause. There are several treatments like cataract surgery, corneal transplants, and eye drops or pills that can help restore vision. However, vision usually cannot be restored for individuals with retinal degeneration or optic nerve damage.
Researchers continue to develop new and innovative methods to restore sight including studies into gene therapy, stem cells, and artificial sight.
Regularly scheduled comprehensive eye exams are recommended to maintain eye health and detect vision problems at the earliest stage.