Colour blind people have less numbers of particular cones than normal, so they get colours confused. Some people are more colour blind than others. Web accessibility issues for individuals who are color blind often involve color combinations that are not properly coordinated or do not provide high contrast. Images without alternative text are also an inconvenience, particularly when the individual is not able to discern what the image is due to the nature of his or her blindness. You can learn more about color blindness at the Lighthouse International Web site .
Blindness comes in a variety of degrees.
Most people defined as being blind often do have a measure of sight, as limited as it might be. A person who is completely sightless is considered to be blind . Many diseases and conditions contribute to or cause blindness including cataracts, cerebral palsy, diabetes, glaucoma, and multiple sclerosis. Many of these conditions are more prevalent as we age. Web accessibility for people who are blind is a considerable challenge based on the obvious fact that the Web is a visual interface.