Classification
United Kingdom
Severely sight impaired * Defined as having central visual acuity of less than 3/60 with normal fields of vision, or gross visual field restriction. * Unable to see at what the normally sighted person sees at . Sight impaired * Able to see at , but not at , what the normally sighted person sees at * Less severe visual impairment is not captured by registration data, and its prevalence is difficult to quantify Low vision * A visual acuity of less than 6/18 but greater than 3/60. * Not eligible to drive and may have difficulty recognising faces across a street, watching television, or choosing clean, unstained, co-ordinated clothing. In the UK, the Certificate of Vision Impairment (CVI) is used to certify patients as severely sight impaired or sight impaired. The accompanying guidance for clinical staff states: "The National Assistance Act 1948 states that a person can be certified as severely sight impaired if they are 'so blind as to be unable to perform any work for which eye sight is essential'". Certification is based on whether a person can do any work for which eyesight is essential, not just one particular job (such as their job before becoming blind). In practice, the definition depends on individuals'United States
In the United States, any person with vision that cannot be corrected to better than 20/200 in the best eye, or who has 20 degrees (Temporary vision impairment
Vision impairment for a few seconds, or minutes, may occur due to any of a variety of causes, some serious and requiring medical attention.Health effects
General functioning
Visual impairments may take many forms and be of varying degrees. Visual acuity alone is not always a good predictor of an individual's function. Someone with relatively good acuity (e.g., 20/40) can have difficulty with daily functioning, while someone with worse acuity (e.g., 20/200) may function reasonably well if they have low visual demands. It is also important to note that best-corrected visual acuity differs from presenting visual acuity; a person with a "normal" best corrected acuity can have "poor" presenting acuity (e.g. individual who has uncorrected refractive error). Thus, measuring an individual's general functioning depends on one's situational and contextual factors, as well as access to treatment. TheMobility
Older adults with visual impairment are at an increased risk of physical inactivity, slower gait speeds, and fear of falls. Physical activity is a useful predictor of overall well-being, and routine physical activity reduces the risk of developing chronic diseases and disability. Older adults with visual impairment (including glaucoma, age-related macular degeneration, and diabetic retinopathy) have decreased physical activity as measured with self-reports and accelerometers. The USCognitive
Older adults with vision loss are at an increased risk of memory loss, cognitive impairment, and cognitive decline.Social and psychological
Studies demonstrate an association between older adults with visual impairment and a poor mental health; discrimination was identified as one of the causes of this association. Older adults with visual impairment have a 1.5-fold risk of reporting perceived discrimination and of these individuals, there was a 2-fold risk of loneliness and 4-fold risk of reporting a lower quality of life. Among adults with visual impairment, the prevalence of moderate loneliness is 28.7% (18.2% in general population) and prevalence of severe loneliness is 19.7% (2.7% in general population). The risk of depression and anxiety are also increased in the visually impaired; 32.2% report depressive symptoms (12.01% in general population), and 15.61% report anxiety symptoms (10.69% in general population). The subjects making the most use of rehabilitation instruments, who lived alone, and preserved their own mobility and occupation were the least depressed, with the lowest risk of suicide and the highest level of social integration. Those with worsening sight and the prognosis of eventual blindness are at comparatively high risk of suicide and thus may be in need of supportive services. Many studies have demonstrated how rapid acceptance of the serious visual impairment has led to a better, more productive compliance with rehabilitation programs. Moreover, psychological distress has been reported to be at its highest when sight loss is not complete, but the prognosis is unfavorable. Therefore, early intervention is imperative for enabling successful psychological adjustment.Associated conditions
Blindness can occur in combination with such conditions asCause
The most common causes of visual impairment globally in 2010 were: #Cataracts
Glaucoma
Infections
Injuries
Genetic defects
People withPoisoning
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 substancesOther
* Amblyopia: is a category of vision loss or visual impairment that is caused by factors unrelated to refractive errors or coexisting ocular diseases. Amblyopia is the condition when a child's visual systems fail to mature normally because the child either has been born premature, 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. *Diagnosis
It is important that people be examined by someone specializing in low vision care prior to other rehabilitation training to rule out potential medical or surgical correction for the problem and to establish a careful baseline refraction and prescription of both normal and low vision glasses and optical aids. Only a doctor is qualified to evaluate visual functioning of a compromised visual system effectively. ThePrevention
The World Health Organization estimates that 80% of visual loss is either preventable or curable with treatment. This includes cataracts, onchocerciasis, trachoma, glaucoma, diabetic retinopathy, uncorrected refractive errors, and some cases of childhood blindness. The Center for Disease Control and Prevention estimates that half of blindness in the United States is preventable.Management
Mobility
Reading and magnification
Computers and mobile technology
Access technology such as screen readers,Other aids and techniques
Blind people may use talking equipment such asEpidemiology
TheSociety and culture
Legal definition
To determine which people qualify for special assistance because of their visual disabilities, various governments have specific definitions for legal blindness. In North America and most ofLiterature and art
Antiquity
The Moche people of ancientModern times
Sports
Blind and partially sighted people participate in sports, such asMetaphorical uses
The word "blind" (adjective and verb) is often used to signify a lack of knowledge of something. For example, aResearch
A 2008 study tested the effect of usingOther animals
Statements that certain species of mammals are "born blind" refers to them being born with their eyes closed and their eyelids fused together; the eyes open later. One example is the rabbit. In humans, the eyelids are fused for a while before birth, but open again before the normal birth time; however, verySee also
*References
External links
* * {{DEFAULTSORT:Visual impairment Articles containing video clips Eye diseases Wikipedia medicine articles ready to translate Wikipedia neurology articles ready to translate