Flash can create many accessibility problems for blind and visually impaired users, particularly those using screen readers. However despite this Flash contains many accessibility features it can present information in different ways. Flash provides keyboard access so that Flash movies can be operated via the keyboard and the majority of Flash content is audio, which means that blind and visually impaired users do not require a screen reader in order to be able to access Flash content. There are also additional steps that a web developer can take to make Flash content accessible to blind and visually impaired users.
A web developer can assist a visually impaired user by ensuring that the Flash content has good contrast and can be enlarged. Meanwhile a web developer can assist a blind user by ensuring that screen readers can access the Flash content. If this is not possible then an equivalent alternative should be provided. A web developer should also ensure that any Flash content can be accessed via the keyboard, a web developer should also provide text equivalents for all non-text elements. Despite these accessibility options the accessibility of Flash content to blind and visually impaired users is sometimes out of the web developers control.
Web Accessibility in Mind contains a very good tutorial, which goes into great depth about the accessibility features of Flash .