I said audio because you alluded it would help those that were seeing impaired. I'm no expert on the matter but I's assume only if done properly with the seeing impaired in mind, most video made for the general public is going to be of no use to the seeing impaired. For example, you're doing a product demonstration and it includes a section that visually shows how fast something can be done without any descriptive narration.
An audio file or video file specifically made to meet the needs for those with impairments on the other hand could have great benefits for them. a very descriptive narration or a video that includes subtitles.