The most common causes of<unk>  globally in 2010 were: #Refractive error (42%) #Cataract (33%) #Glaucoma (2%) #Age-related macular degeneration (1%) #Corneal opacification (1%) #Diabetic retinopathy (1%) #Childhood blindness #Trachoma (1%) #Undetermined (18%) The most common causes of blindness worldwide in 2010 were: #Cataracts (51%) #Glaucoma (8%) #Age-related macular degeneration (5%) #Corneal opacification (4%) #Childhood blindness (4%) #Refractive errors (3%) #Trachoma (3%) #Diabetic retinopathy (1%) #Undetermined (21%) About 90% of people who are<unk> ly impaired live in the developing world. Age-related macular degeneration, glaucoma, and diabetic retinopathy are the leading causes of blindness in the developed world. Among working-age adults who are newly blind in England and Wales the most common causes in 2010 were: #Hereditary retinal disorders (20.2%) #Diabetic retinopathy (14.4%) #Optic atrophy (14.1%) #Glaucoma (5.9%) #Congenital abnormalities (5.1%) #Disorders of the<unk>  cortex (4.1%) #Cerebrovascular disease (3.2%) #Degeneration of the macula and posterior pole (3.0%) #Myopia (2.8%) #Corneal disorders (2.6%) #Malignant neoplasms of the brain and nervous system (1.5%) #Retinal detachment (1.4%) Cataracts Cataracts are the greying or opacity of the crystalline lens, which can be caused in children by intrauterine infections, metabolic disorders, and genetically transmitted syndromes. Cataracts are the leading cause of child and adult blindness that doubles in prevalence with every ten years after the age of 40. Consequently, today cataracts are more common among adults than in children. That is, people face higher chances of developing cataracts as they age. Nonetheless, cataracts tend to have a greater financial and emotional toll upon children as they must undergo expensive diagnosis, long term rehabilitation, and<unk>  assistance. Also, according to the Saudi Journal for Health Sciences, sometimes patients experience irreversible amblyopia after pediatric cataract surgery because the cataracts prevented the normal maturation of vision prior to operation. Despite the great progress in treatment, cataracts remain a global problem in both economically developed and developing countries. At present, with the variant outcomes as well as the unequal access to cataract surgery, the best way to reduce the risk of developing cataracts is to avoid smoking and extensive exposure to sun light (i.e. UV-B rays). Glaucoma Glaucoma is an eye disease often characterized by increased pressure within the eye or intraocular pressure (IOP). Glaucoma causes<unk>  field loss as well as severs the optic nerve. Early diagnosis and treatment of glaucoma in patients is imperative because glaucoma is triggered by non-specific levels of IOP. Also, another challenge in accurately diagnosing glaucoma is that the disease has four causes: 1) inflammatory ocular hypertension syndrome (IOHS); 2) severe uveitic angle closure; 3) corticosteroid-induced; and 4) a heterogonous mechanism associated with structural change and chronic inflammation. In addition, often pediatric glaucoma differs greatly in cause and management from the glaucoma developed by adults. Currently, the best sign of pediatric glaucoma is an IOP of 21 mm Hg or greater present within a child. One of the most common causes of pediatric glaucoma is cataract removal surgery, which leads to an incidence rate of about 12.2% among infants and 58.7% among 10-year-olds. Infections The burden of onchocerciasis: children leading blind adults in Africa Childhood blindness can be caused by conditions related to pregnancy, such as congenital rubella syndrome and retinopathy of prematurity. Leprosy and onchocerciasis each blind approximately 1 million individuals in the developing world. The number of individuals blind from trachoma has decreased in the past 10 years from 6 million to 1.3 million, putting it in seventh place on the list of causes of blindness worldwide. Central corneal ulceration is also a significant cause of monocular blindness worldwide, accounting for an estimated 850,000 cases of corneal blindness every year in the Indian subcontinent alone. As a result, corneal scarring from all causes is now the fourth greatest cause of global blindness. Injuries Re-educating wounded. Blind French soldiers learning to make baskets, World War I. Eye injuries, most often occurring in people under 30, are the leading cause of monocular blindness (vision loss in one eye) throughout the United States. Injuries and cataracts affect the eye itself, while abnormalities such as optic nerve hypoplasia affect the nerve bundle that sends signals from the eye to the back of the brain, which can lead to decreased<unk>  acuity. Cortical blindness results from injuries to the occipital lobe of the brain that prevent the brain from correctly receiving or interpreting signals from the optic nerve. Symptoms of cortical blindness vary greatly across individuals and may be more severe in periods of exhaustion or stress. It is common for people with cortical blindness to have poorer vision later in the day. Blinding has been used as an act of vengeance and torture in some instances, to deprive a person of a major sense by which they can navigate or interact within the world, act fully independently, and be aware of events surrounding them. An example from the classical realm is Oedipus, who gouges out his own eyes after realizing that he fulfilled the awful prophecy spoken of him. Having crushed the Bulgarians, the Byzantine Emperor Basil II blinded as many as 15,000 prisoners taken in the battle, before releasing them. Contemporary examples include the addition of methods such as acid throwing as a form of disfigurement. Genetic defects People with albinism often have vision loss to the extent that many are legally blind, though few of them actually cannot see. Leber congenital amaurosis can cause total blindness or severe sight loss from birth or early childhood. Retinitis pigmentosa is characterized by decreased peripheral vision and trouble seeing at night. Advances in mapping of the human genome have identified other genetic causes of low vision or blindness. Two such examples are Bardet–Biedl syndrome . Poisoning Rarely, blindness is caused by the intake of certain chemicals. A well-known example is methanol, which is only mildly toxic and minimally intoxicating, and breaks down into the substances formaldehyde and formic acid which in turn can cause blindness, an array of other health complications, and death. When competing with ethanol for metabolism, ethanol is metabolized first, and the onset of toxicity is delayed. Methanol is commonly found in methylated spirits, denatured ethyl alcohol, to avoid paying taxes on selling ethanol intended for human consumption. Methylated spirits are sometimes used by alcoholics as a desperate and cheap substitute for regular ethanol alcoholic beverages. Other * Amblyopia: is a category of vision loss or<unk>  that is caused by factors unrelated to refractive errors or coexisting ocular diseases. Amblyopia is the condition when a child's<unk>  systems fail to mature normally because the child either suffers from a premature birth, measles, congenital rubella syndrome, vitamin A deficiency, or meningitis. If left untreated during childhood, amblyopia is currently incurable in adulthood because surgical treatment effectiveness changes as a child matures. Consequently, amblyopia is the world's leading cause of child monocular vision loss, which is the damage or loss of vision in one eye. In the best case scenario, which is very rare, properly treated amblyopia patients can regain 20/40 acuity. * Corneal opacification * Degenerative myopia * Diabetic retinopathy: is one of the manifestation microvascular complications of diabetes, which is characterized by blindness or reduced acuity. That is, diabetic retinopathy describes the retinal and vitreous hemorrhages or retinal capillary blockage caused by the increase of A1C, which a measurement of blood glucose or sugar level. In fact, as A1C increases, people tend to be at greater risk of developing diabetic retinopathy than developing other microvascular complications associated with diabetes (e.g. chronic hyperglycemia, diabetic neuropathy, and diabetic nephropathy). Despite the fact that only 8% of adults 40 years and older experience vision-threatening diabetic retinopathy (e.g. nonproliferative diabetic retinopathy or NPDR and proliferative diabetic retinopathy or PDR), this eye disease accounted for 17% of cases of blindness in 2002. * Retinitis pigmentosa * Retinopathy of prematurity: The most common cause of blindness in infants worldwide. In its most severe form, ROP causes retinal detachment, with attendant<unk>  loss. Treatment is aimed mainly at prevention, via laser or Avastin therapy. * Stargardt's disease * Uveitis: is a group of 30 intraocular inflammatory diseases caused by infections, systemic diseases, organ-specific autoimmune processes, cancer or trauma. That is, uveitis refers to a complex category of ocular diseases that can cause blindness if either left untreated or improperly diagnosed. The current challenge of accurately diagnosing uveitis is that often the cause of a specific ocular inflammation is either unknown or multi-layered. Consequently, about 3–10% uveitis victims in developed countries, and about 25% of victims in the developing countries, become blind from incorrect diagnosis and from ineffectual prescription of drugs, antibiotics or steroids. In addition, uveitis is a diverse category of eye diseases that are subdivided as granulomatous (or tumorous) or non-granulomatous anterior, intermediate, posterior or pan uveitis. In other words, uveitis diseases tend to be classified by their anatomic location in the eye (e.g. uveal tract, retina, or lens), as well as can create complication that can cause cataracts, glaucoma, retinal damage, age-related macular degeneration or diabetic retinopathy. *Xerophthalmia, often due to vitamin A deficiency, is
Visual impairment
Dyslexia
Vision disorder
Sexual dysfunction
Cognitive disorder
Cognitive deficit
Cortical blindness
Color blindness