Visual impairment in the context of Mobility aid

Louis Braille (/breɪl/ brayl; French: [lwi bʁɑj]; 4 January 1809 – 6 January 1852) was a French educator and the inventor of a reading and writing system named after him, braille, intended for use by visually impaired people. His system is used worldwide and remains virtually unchanged to this day.

Braille was blinded in one eye at the age of three. This occurred as a result from an accident with a stitching awl in his father's harness-making shop. Consequently, an infection set in and spread to both eyes, resulting in total blindness. At that time, there were not many resources in place for the blind, but he nevertheless excelled in his education and received a scholarship to France's Royal Institute for Blind Youth. While still a student there, he began developing a system of tactile code that could allow blind people to read and write quickly and efficiently. Inspired by a system invented by Charles Barbier, Braille's new method was more compact and lent itself to a range of uses, including music. He presented his work to his peers for the first time in 1824, when he was fifteen years old.

The visual system is the physiological basis of visual perception (the ability to detect and process light). The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment. The visual system is associated with the eye and functionally divided into the optical system (including cornea and lens) and the neural system (including the retina and visual cortex).

The visual system performs a number of complex tasks based on the image forming functionality of the eye, including the formation of monocular images, the neural mechanisms underlying stereopsis and assessment of distances to (depth perception) and between objects, motion perception, pattern recognition, accurate motor coordination under visual guidance, and colour vision. Together, these facilitate higher order tasks, such as object identification. The neuropsychological side of visual information processing is known as visual perception, an abnormality of which is called visual impairment, and a complete absence of which is called blindness. The visual system also has several non-image forming visual functions, independent of visual perception, including the pupillary light reflex and circadian photoentrainment.

The 1992 Paralympic Winter Games (French: Jeux paralympiques d'hiver de 1992) were the fifth Winter Paralympics. They were the first Winter Paralympics to be celebrated with the International Olympic Committee cooperation. They were also the first ever Paralympics or a Winter Parasports event held in France. They were held at the resort of Tignes as a support venue of the main host city Albertville, France, from 25 March to 1 April 1992. For the first time, demonstration events in Alpine and Nordic Skiing for athletes with an intellectual disability and Biathlon for athletes with a visual impairment were held.

Deafblindness is a condition of little or no useful hearing and little or no useful sight. According to the "Nordic definition", "deafblindness is a combined vision and hearing impairment of such severity that it is hard for the impaired senses to compensate for each other. Thus, deafblindness is a distinct disability." Different degrees of vision loss and auditory loss occur within each individual. Because of this inherent diversity, each deafblind individual's needs regarding lifestyle, communication, education, and work need to be addressed based on their degree of dual-modality deprivation, to improve their ability to live independently. In 1994, an estimated 35,000–40,000 United States residents were medically deafblind. Laura Bridgman was the first American deafblind person known to become well educated. Helen Keller was a well-known example of an educated deafblind individual. To further her lifelong mission to help the deafblind community to expand its horizons and gain opportunities, the Helen Keller National Center for Deaf-Blind Youths and Adults (also called the Helen Keller National Center or HKNC), with a residential training program in Sands Point, New York, was established in 1967 by an act of Congress.

The deafblind community has its own culture, comparable to those of the Deaf community. Members of the deafblind community have diverse backgrounds but are united by similar experiences and a shared, homogeneous understanding of what it means to be deafblind. Some deafblind individuals view their condition as a part of their identity.

A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or double vision, halos around light, trouble with bright lights, and difficulty seeing at night. This may result in trouble driving, reading and recognizing faces. Poor vision caused by cataracts may also result in an increased risk of falling and depression. In 2020 Cataracts caused 39.6% of all cases of blindness and 28.3% of visual impairment worldwide. Cataracts remain the single most common cause of global blindness.

Cataracts are most commonly due to aging but may also be due to trauma or radiation exposure, be present from birth or occur following eye surgery for other problems. Risk factors include diabetes, longstanding use of corticosteroid medication, smoking tobacco, prolonged exposure to sunlight and alcohol. In addition, poor nutrition, obesity, chronic kidney disease and autoimmune diseases have been recognized in various studies as contributing to the development of cataracts. Cataract formation is primarily driven by oxidative stress, which damages lens proteins, leading to their aggregation and the accumulation of clumps of protein or yellow-brown pigment in the lens. This reduces the transmission of light to the retina at the back of the eye, impairing vision. Additionally, alterations in the lens's metabolic processes, including imbalances in calcium and other ions, contribute to cataract development. Diagnosis is typically through an eye examination, with ophthalmoscopy and slit-lamp examination being the most effective methods. During ophthalmoscopy the pupil is dilated and the red reflex is examined for any opacities in the lens. Slit-lamp examination provides further details on the characteristics, location and extent of the cataract.

Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between 28 and 32 weeks, early preterm birth occurs between 32 and 34 weeks, late preterm birth is between 34 and 36 weeks' gestation. These babies are also known as premature babies or colloquially preemies (American English) or premmies (Australian English). Symptoms of preterm labor include uterine contractions which occur more often than every ten minutes and/or the leaking of fluid from the vagina before 37 weeks. Premature infants are at greater risk for cerebral palsy, delays in development, hearing problems and problems with their vision. The earlier a baby is born, the greater these risks will be.

The cause of spontaneous preterm birth is often not known. Risk factors include diabetes, high blood pressure, multiple gestation (being pregnant with more than one baby), being either obese or underweight, vaginal infections, air pollution exposure, tobacco smoking, and psychological stress. For a healthy pregnancy, medical induction of labor or cesarean section are not recommended before 39 weeks unless required for other medical reasons. There may be certain medical reasons for early delivery such as preeclampsia.

Cortical visual impairment (CVI) is a form of visual impairment that is caused by a brain problem rather than an eye problem. (The latter is sometimes termed "ocular visual impairment" when discussed in contrast to cortical visual impairment.) Some people have both CVI and a form of ocular visual impairment.

CVI is also sometimes known as cortical blindness, although most people with CVI are not totally blind. The term neurological visual impairment (NVI) covers both CVI and total cortical blindness. Delayed visual maturation, another form of NVI, is similar to CVI, except the child's visual difficulties resolve in a few months. Though the vision of a person with CVI may change, it rarely if ever becomes totally normal.

The Institut National des Jeunes Aveugles (INJA; National Institute for Blind Youth) is a special school for blind students in Paris, France. It is considered the first school for the blind in the Western world, and has served as a model for many subsequent schools for blind students.

Microangiopathy (also known as microvascular disease, small vessel disease (SVD) or microvascular dysfunction) is a disease of the microvessels, small blood vessels in the microcirculation. It can be contrasted to macroangiopathies such as atherosclerosis, where large and medium-sized arteries (e.g., aorta, carotid and coronary arteries) are primarily affected.

Small vessel diseases (SVDs) affect primarily organs that receive significant portions of cardiac output such as the brain, the kidney, and the retina. Thus, SVDs are a major etiologic cause in debilitating conditions such as renal failure, blindness, lacunar infarcts, and dementia.

Faith healing is the practice of prayer and gestures (such as laying on of hands) that are believed by some to elicit divine intervention in spiritual and physical healing, especially the Christian practice. Believers assert that the healing of disease and disability can be brought about by religious faith through prayer or other rituals that, according to adherents, can stimulate a divine presence and power. Religious belief in divine intervention does not depend on empirical evidence of an evidence-based outcome achieved via faith healing. Virtually all scientists and philosophers dismiss faith healing as pseudoscience.

Claims that "a myriad of techniques" such as prayer, divine intervention, or the ministrations of an individual healer can cure illness have been popular throughout history. There have been claims that faith can cure blindness, deafness, cancer, HIV/AIDS, developmental disorders, anemia, arthritis, corns, defective speech, multiple sclerosis, skin rashes, total body paralysis, and various injuries. Recoveries have been attributed to many techniques commonly classified as faith healing. It can involve prayer, a visit to a religious shrine, or simply a strong belief in a supreme being.

Near visual acuity or near vision is a measure of how clearly a person can see nearby small objects or letters. Visual acuity in general usually refers clarity of distance vision, and is measured using eye charts like Snellen chart, LogMAR chart etc. Near vision is usually measured and recorded using a printed hand-held card containing different sized paragraphs, words, letters or symbols. Jaeger chart, N notation reading chart and Snellen's near vision test are the commonly used charts for measuring and recording near visual acuity. Near vision testing is usually done after correcting visual acuity at a distance.

Eye conditions like presbyopia, accommodative insufficiency, cycloplegia etc. can affect the near visual acuity. According to the World Health Organization, the near visual acuity less than N6 or M0.8 at 40 cm is classified as near visual impairment.

Guide dogs (colloquially known in the US as seeing-eye dogs) are assistance dogs trained to lead people who are blind or visually impaired around obstacles. Although dogs can be trained to navigate various obstacles, they are red–green colour blind and incapable of interpreting street signs. The human does the directing, based on skills acquired through previous mobility training. The handler might be likened to an aircraft's navigator, who must know how to get from one place to another, and the dog is the pilot, who gets them there safely. In several countries guide dogs, along with most other service and hearing dogs, are exempt from regulations against the presence of animals in places such as restaurants and public transportation.

A monocular is a compact refracting telescope used to magnify images of distant objects, typically using an optical prism to ensure an erect image, instead of using relay lenses like most telescopic sights. The volume and weight of a monocular are typically less than half of a pair of binoculars with similar optical properties, making it more portable and also less expensive. This is because binoculars are essentially a pair of monoculars packed together — one for each eye. As a result, monoculars only produce two-dimensional images, while binoculars can use two parallaxed images (each for one eye) to produce binocular vision, which allows stereopsis and depth perception.

Monoculars are ideally suited to those applications where three-dimensional perception is not needed, or where compactness and low weight are important (e.g. hiking). Monoculars are also sometimes preferred where difficulties occur using both eyes through binoculars due to significant eyesight variation (e.g. strabismus, anisometropia or astigmatism) or unilateral visual impairment (due to amblyopia, cataract or corneal ulceration).

Retinal detachment is a condition where the retina pulls away from the tissue underneath it. It may start in a small area, but without quick treatment, it can spread across the entire retina, leading to serious vision loss and possibly blindness. Retinal detachment is a medical emergency that requires surgery.

The retina is a thin layer at the back of the eye that processes visual information and sends it to the brain. When the retina detaches, common symptoms include seeing floaters, flashing lights, a dark shadow in vision, and sudden blurry vision. The most common type of retinal detachment is rhegmatogenous, which occurs when a tear or hole in the retina lets fluid from the center of the eye get behind it, causing the retina to pull away.

A touch user interface (TUI) is a computer-pointing technology based upon the sense of touch (haptics). Whereas a graphical user interface (GUI) relies upon the sense of sight, a TUI enables not only the sense of touch to innervate and activate computer-based functions, it also allows the user, particularly those with visual impairments, an added level of interaction based upon tactile or Braille input.