Blindness is defined as a lack of vision in varying degrees from impairment to complete loss of vision. Some doctors defined blindness as the inability to use glasses or corrective lenses to correct the loss of vision.
In America, legal blindness is classified as corrected visual acuity of 20/200 or less, or a visual field of up to 20°. Many legally blind individuals qualify to receive benefits from federal and state governments even if they still have some usable vision. Colloquially, there up to 400 million individuals who suffer from impaired or total vision loss by various causes. More than 50 million individuals have total blindness and cannot see in either eye.
Some individuals suffered partial blindness, meaning they have very limited vision. Total blindness (absolute blindness) typically means the individual cannot see light or tell the difference between dark and light even when bright lights are shined into the patient’s eyes.
Color Blindness and Night Blindness
Many males and some females suffer from color blindness and cannot perceive varying shades of colors, especially red and green. Color blindness is not an actual blindness, but a visual condition caused by a genetic predisposition inherited from ancestors. Generally, those who suffer from color blindness typically have normal vision.
Night blindness usually produces significant visual challenges under decreasing illumination indoors or out. This condition can be caused by a genetic predisposition or acquired over time through physical or external conditions. The diminished status of sight involving night blindness is often affected only under abnormal lighting conditions.
Snow blindness is a condition caused by excessive levels of ultraviolet light that produces a typically temporary condition when the corneal surface cells begin to swell. Even extreme cases of snow blindness leave the individual with the ability to observe movement and shapes.
Some Causes of Blindness
A variety of conditions and diseases can cause vision loss. In America, the leading causes of visual loss include:
An injury or accident occurring on the eye surface from a chemical burn, auto accidents, or sports injury
- Macular Degeneration
- Blocked blood vessels
- Lazy eye
- Optic neuritis
- Eye surgery complications
- Medication errors or drugs
- Retrolental Fibroplasia (premature birth complications)
- Retinitis Pigmentosa
- Optic Glioma, Retinal Blastoma, or other tumors
- Severe head injury or trauma
- End-stage diabetic retinopathy
- End-stage glaucoma
- A stroke in the eye (vascular occlusion)
- Cornea infection
- Endophthalmitis (severe infection of the internal eye)
While some individuals cannot see at all, this condition may be temporary blindness that can be reversed over time by treating an infection, surgical procedures, or an improvement of visual loss. You can make an accurate diagnosis of blindness confirmed by an ophthalmologist through physical examination of all components of the eye.
Common Forms of Legal Blindness
Age-Related Macular Degeneration
Many individuals suffer from age-related macular degeneration (AMD), a debilitating disease that affects the patient’s central vision. The degeneration involves the macula (the central part of the retina) that has been severely damaged in both eyes. In some cases, the individual has peripheral vision intact and can see movement or shapes and read large letters under certain conditions.
Individuals with age-related macular degeneration can decrease the risk of partial or total blindness by quitting smoking, consuming a diet rich in vegetables and fruits, and eating sardines and salmon at least twice a week to receive nutritional benefit. Doctors can also treat AMD by injecting medicine into the eye to stop or slow the progression of vision loss associated with the condition.
The eye’s retina can be affected by a rare genetic disease that can lead to blindness. Many individuals suffering from tunnel vision caused by retinitis pigmentosa usually see only a small, limited and narrow window of vision. These individuals might have 20/20 eyesight through the narrow tunnel but have a very small visual field.
The University of Pennsylvania has developed retinal gene therapy approved by the FDA to treat Leber’s congenital amaurosis, a hereditary retinal disease. In the years ahead, advancing gene therapy will likely assist many others who are legally blind and suffer from acquired and hereditary eye diseases.
Diabetic retinopathy can also cause legal blindness where patients lose vision from bleeding or swelling in the retina or by the detachment of the retina from the eye. Many diabetic individuals work to decrease the risk of becoming legally blind through annual eye exams and controlling blood sugar and blood pressure levels.
Glaucoma is a serious disease affecting the eye when retinal neurons sending signals from the eye to the brain begin to die. Progression of diminishing loss of the field of vision can be stopped or slowed using effective medications and proven surgical procedures to treat glaucoma. Typically, individuals who have been diagnosed and treated with the condition early on have an increased chance of preserving their eyesight compared to those who wait.
A severe cataract causing cloudiness in the lens can cause the individual’s visual acuity to drop significantly. The cataract restricts light emitting into the retina at the back of the eye. Fortunately, in recent years, doctors have been able to surgically remove damaged cataracts and the cloudy lens and replace it with a clear synthetic one that results in significantly improved overall vision.
Blindness Risk Factors
Blindness has a principal risk factor to individuals living in Third World areas that do not have ready access to effective medical care. However, other significant risk factors can affect an individual’s eyesight, including poor or a lack of prenatal care, premature birth, labor and delivery complications, poor nutrition, advancing age, and a failure to wear safety glasses when necessary (when working with power tools). Other risk factors include smoking, poor hygiene, familial association (genetics) of blindness, and the presence of ocular diseases.
Individuals with hypertension, diabetes mellitus, cardiovascular disease, and cerebrovascular disease also have a heightened risk factor for developing progressing blindness.
The doctor can diagnose blindness by testing the patient’s eyes individually. The ophthalmologists usually measure the individual’s visual acuity and peripheral (side vision) field of vision. Some individuals can have unilateral blindness (one eye) or bilateral blindness (both eyes).
The onset of poor vision can be chronic, progressive, acute, or temporary. Fortunately, temporary blindness differs significantly from a permanent condition that might be irreversible even with access to numerous surgical, medical, and equipment options.
Ophthalmologists typically have various treatments for visual blindness or visual impairment based on the cause of the condition. When nutritional factors cause blindness, the patient’s doctor can address significant dietary changes to improve visual acuity. Cataracts can be corrected using surgical procedures to restore nearly 100% of their eyesight.
Infectious or inflammatory causes of total or permanent blindness can be treated with effective drugs taken in pill form or eyedrops. The doctor may be able to perform a corneal transplantation when corneal scarring has occurred.
The prognosis for total or permanent blindness is highly dependent on what caused the condition and what treatment has already been provided. If the individual suffered a stroke or optic nerve damage, the restoration of visual acuity is often limited or nonexistent. Ongoing retinal detachment in patientsusually can not be improved even under the best surgical repair. Cataract or corneal replacement usually produces good prognoses in both the young and old.
Preventing blindness usually requires a combination of immediate access to quality medical care and education on maintaining optimal visual acuity. Many traumatic causes of temporary blindness can be prevented if the individual uses effective protection. Extensive debilitating blindness caused by glaucoma can be prevented through early detection and receiving proper treatment. Diabetic retinopathy is easily preventable if the individual controls blood sugar levels, avoids obesity, does not smoke, maintains exercise routines, and places emphasis on consuming the best foods without increasing sugar levels.