Visual Impairments & Assistive Technology: This video explains different Assistive Technology tools for people with low vision.

This video explains different Assistive Technology tools for people with low vision.

Visual Impairment and Blindness

Blindness is the condition of lacking visual perception due to physiological or neurological factors.

Total blindness is the complete lack of form and light perception and is clinically recorded as "NLP," an abbreviation for "no light perception.

In order to determine which people may need special assistance because of their visual disabilities, various governmental jurisdictions have formulated more complex definitions referred to as legal blindness.

Blindness rarely means total absence of light perception. Most definitions of blindness are based on measurement of visual acuity (the ability to read letters at a certain distance) and assessment of the ability of the person to carry out tasks needing vision.

Visual acuity is usually tested by asking the patient to read letters of various sizes on a chart viewed from a distance of 6 m or 20 feet (the Snellen method).

Acuity is expressed as a fraction, the number on top referring to the distance at which a normal person can read a particular size of letter and the lower number the distance at which the subject being tested can read that size of letter.

Hence normal visual acuity is 6/6 (European) or 20/20 (American).

A person should be certified blind if the visual acuity (while wearing corrective glasses) is 3/60 or below (when a letter that can be recognized from 60 metres by a normal person can be identified only from 3 metres or closer).

A person should also be certified blind if their acuity is between 3/60 and 6/60 but they have completely lost the peripheral part of their visual field, hence restricting their vision to the central part of the field.

Indeed, if the more useful lower part of the visual field is lost then someone with better than 6/60 acuity can be certified blind.

Eye injuries, most often occurring in people under 30, are the leading cause of monocular blindness (vision loss in one eye).Visually impaired and blind people have devised a number of techniques that allow them to complete daily activities using their remaining senses.

Recent access technology such as screen reading software enable the blind to use mainstream computer applications including the Internet.

www.answers.com

Common Causes of Visual Impairment

Lack of vitamin A
Lack of vitamin A has a direct effect on the eye, causing clouding and softening of the cornea (keratomalacia), but also increases the risk and severity of infections, so that measles can be a blinding or even fatal disease in children who are deficient in vitamin A. Night-blindness due to lack of vitamin A may occur in famines, and cure of this condition by eating liver, which is rich in vitamin A, has been known for over 3000 years.

Pigmentary degeneration of the retina (retinitis pigmentosa)
Another cause of night-blindness is pigmentary degeneration of the retina (retinitis pigmentosa) which, combined with partial loss of the visual field, eventually contracting down to tunnel vision, can be most disabling. This condition is mainly inherited as an autosomal recessive condition (showing itself only when both parents carry the mutant gene), but other forms occur. The disorder is progressive and untreatable.

Trachoma
Trachoma, an infectious disease, affects some 500 million people world-wide, of whom 7 million are blind and 10 million visually impaired. The infectious agents are bacteria known as Chlamydia.

River Blindness
River blindness (onchocerciasis) is the next commonest infection, where microfilarial parasites, spread by black flies, which breed in the tropical, sub-Saharan belt across the whole of Africa and at similar latitudes in Mexico, Brazil, and Ecuador, invade the retina and the supporting, vascularized middle layer of the eyeball, the choroid. Treatment was revolutionized in 1987 when ivermectin, already used in veterinary medicine, was registered for human therapy.

Cataracts
Cataracts, age-related macular degeneration (ARMD) is a major cause of blindness, about 40%, but these are essentially treatable by surgery except in those cases where extraction of the cataract reveals underlying, untreatable ARMD.

Glaucoma
Damage to the retina caused by glaucoma (increased pressure in the eyeball) and by diabetes (diabetic retinopathy) make up almost all the remaining causes of blindness. Glaucoma is insidious in onset: acuity in the central visual field is not seriously affected and a diagnosis may not be made until much of the peripheral retina has been destroyed. Diabetic retinopathy is most prevalent and severe in long-standing insulin-dependent diabetes. This emphasizes the importance of striving for optimal diabetic control. Routine screening checks for both glaucoma and diabetic retinopathy are essential, but manpower and economic considerations have led to much of this work being transferred to orthoptists and optometrists.

Retinal detachment
Retinal detachment (separation of the retina from the pigment epithelium behind it) is a rarer cause of blindness.

The Sun
There is a long history of visual upsets from staring directly at the sun. The high energy optically concentrated at the central part of the retina for only seconds can produce prolonged after-images and even permanent loss of central vision. This is an occupational hazard for astronomers, and for members of the public who sun-gaze in a misguided attempt to strengthen their eyes or when under the influence of hallucinogenic drugs. There is a particular hazard during solar eclipses because the reduced total amount of light makes it easier to hold fixation on the sun, but the intensity on the remaining illuminated part of the retina is just as high (and just as damaging) as when there is no eclipse: hence the term eclipse blindness.

www.answers.com

Teaching Strategies for the Visually Impaired

Position in the classroom
If a child is visually impaired but it is correctable to some degree, it is important for the teacher to place that child in a position in the classroom where the child has as much access to the blackboard as possible.

Materials
Special paper with raised lines on it is should be made available for the child to use.

All children with visual impairments should be taught typing, and given access to a keyboard.

For visually impaired children, tasks should be made as concrete as possible. It would be difficult for a visually impaired child to visualize what the teacher means when she said 1/4 of a piece of pie during a lesson on fractions. But, if the child has manipulative in front of them, they will use their sense of touch and this will help to reinforce the concept for the child.

Classroom Environment
The classroom should also be "brailed," that is, Braille labels should be placed throughout the room, and on the various pieces of furniture. The sighted students should also be made aware of how the visually impaired make use of the face of the clock for direction. This will prevent students from saying that the trash can is over there.

It may also be advantageous to have a student volunteer to read out loud to the visually impaired student. You can kill two birds with one stone here by choosing a student who may need some help working up to his potential. By having them read out loud, you can be sure that they are going over the material, and in turn, this should help his grades. The visually impaired child should also have access to a tape recorder. In this way, he can record classroom discussions and transpose his notes into Braille later on.

Current trends in technology have made learning opportunities for the visually impaired even convenient. Hopefully this trend will continue and the technology will continue to improve and come down in cost so that every child with a visual impairment will be provided with every opportunity to succeed in school.

www.helium.com
Author: Tracie Joy

Teacher resource:

Teaching children who are blind or visually impaired
http://www.ed.gov.nl.ca/edu/pub/vi/vi.htm
(Very in Depth)

Assistive Technology Definitions

Screen reader - software program that works in conjunction with a speech synthesizer to provide verbalization of everything on the screen including menus, text, and punctuation.
Screen magnification - software that focuses on a single portion (1/4, 1/9, 1/16, etc.) of the screen and enlarges it to fill the screen.
Refreshable braille display - provide tactile output of information presented on the computer screen. Unlike conventional braille, which is permanently embossed onto paper, refreshable braille displays are mechanical in nature and lift small, rounded plastic pins as need to form braille characters. The displays contain 20, 40, or 80 braille cells, after the line is read, the user can "refresh" the display to read the next line.
Braille translation software - translate text and formatting into appropriate braille characters and formatting.
Braille writing equipment - used for creation of paper braille materials. Can be manual or electronic devices.
Closed-Circuit Television - magnify a printed page through the used of a special television camera with a zoom lens and displays the image on a monitor.
Portable notetaker – small portable units that employ either a braille or standard keyboard to allow the user to enter information. Text is stored in files that cam be read and edited using the built-in speech synthesizer or braille display. File may be sent to a printer or braille embosser, or transferred to a computer.
Braille embosser - a braille printer that embosses computer-generated text as braille on paper.
Scanners - a device that converts an image from a printed page to a computer file. Optical-character-recognition (OCR) software makes the resulting computer file capable of being edited.
Adaptive keyboard - offer a variety of ways to provide input into a computer through various options in size, layout (i.e. alphabetical order), and complexity.
Augmentative communication device - provide speech for people who are not able to communicate verbally. Device may talk, user indicates communication through the use of tactile symbols, auditory scanning, large print symbols, etc.

Visual Impairments & Assistive Technology

This video explains different Assistive Technology tools for people with low vision.

Visual Impairment Links

Famous Visually Impaired People

Visual Impairment Assistive Technology Reference

Visual Impairment and Blindness

Common Causes of Visual Impairment

Teaching Strategies for the Visually Impaired

Assistive Technology Definitions