You’re a developer? Take a look at the article Microsoft has written about Game Accessibility. The article features several important subjects on the accessibility of games and why it’s important for games to be accessible, also from a business perspective.
However, it is a little bit outdated. New technologies have come up and also the graph with predicted growth for Accessible technology users is outdated. With the technology of today, way more is possible ant it’s also interesting to see that today Microsoft’s Xbox has a lot of Accessibility features for gamers with an impairment.
The article from Microsoft can be found here.