This page provides tips and resources for users that have a number of forms of visual impairment
Short-sightedness - Myopia
Long-sightedness - Hyperopia
* Peripheral Blindness
Typical Access methods:
Tactile feedback: Braille, Optical character recognition, forcefeedback
Descriptive video service (DVS see NCAM - CPB/WGBH National Center for Accessible Media @ http://ncam.wgbh.org/)
Enlargement of text or display magnification
Physical features of objects e,g grooves and kinks in keyboards, uniform positioning, texture etc
Touch typing is particularly beneficial to blind people (additional grooves and kinks in keyboard help finger positioning)
Braille also known as soft, refreshable or paperless Braille is produced by an array of electronically controlled moving pins grouped to form standard Braille cells.
Braille software can output the same content to a retractable braille display so that the content can be read by touch.
Permanent output is obtained by using a Braille Embosser.
Optical Character Recognition system (OCR).
With the attachment of a scanner and an OCR package, text can be sent to the PC and with one of the above access devices a user with limited vision is able to read a printed document without any sighted assistance.
Descriptive video service
(DVS see NCAM - CPB/WGBH National Center for Accessible Media @ http://ncam.wgbh.org/)
Available since 1986
DVS extends to narrated descriptions of the key visual elements without interfering with the audio or dialogue of a program or movie. The narration describes visual elements such as actions, settings, body language, graphics, silent situations without interfering with natural flow. This makes video, television and movies more accessible to people who are blind or have low vision
Now extended to digital satellite
Input tools for blind users
Usually by means of voice recognition (voice-to-text) or braille keyboards
Some visual impairments including blindness can be supported by standard keyboards. Grooves in keyboards provide cues. Blind people are particularly sensitive to key clicks which inform user that a key has been pressed.
Sensory input (eye gaze: muscular and retinal recognition; touch � not just braille)
Wearable chips can be used to correct blindness by missing out the front of the eye and transmitting straight to the retina
Accessibility Tips for users with Low vision
See http://www.webaim.org/simulations/lowvision for a low vision simulation
Accessibility tips for short-sighted users
Typically such users:
Cannot see small print
May have difficulty using mouse
May have difficulty in the form of blurred or fogged vision
May have difficult seeing objects outside the centre of the visual field or in some parts of the visual field
May have difficulty in the form of tunnel vision
May have greater difficulty with glare and night blindness than users without low vision
Design solutions for short-sighted users
The area of focus must be enlarged or otherwise enhanced
A zoom feature is required which allows the screen to be viewed at different levels of detail and of magnification
Information that forms a semantic whole must organised in such a manner that it is clustered at the centre of vision
Fonts, colours, and cursors should be adjustable to make them more visible
The contrast between text and background must be high
Text must not be placed over a patterned background where the two might interfere with each other
A consistent or predictable layout must be used for screens and dialogs.
The default line width used during drawing lines should be adjustable (if such information is provided by the system
Accessibility Tips for Long-sightedness users
Accessibility tips for users who wear bifocals
Accessibility tips for users with photosensitive epilepsy
Typically such users:
May have difficulty in the form of seizures triggered by flickering or flashing in the 4-59 flashes per second (HERTZ) range including changes from dark to light (like strobe lights). Peak sensitivity is at 20 flashes per second
Design solutions for users with photosensitive epilepsy
Flashing presentation must be avoided
All objects with flashing and animation capability must be supported by an option to switch them off.
Colour should be used sparingly � Colour can create noise and be source of fatigue due to requirement for refocusing especially with highly saturated colours such as full red or deep blue
|Ai Squared||Ai Squared Home|
|Royal National Institute for the Blind (RNIB)||http://www.rnib.org.uk/
|Royal Victoria Institute for Blind (RVIB)|| http://www.rvib.org.au
These pages were created by Kristina Masuwa-Morgan (© CCCU, last updated
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