There are an infinite number of possible disabilities. Most disabled people already have tools to accommodate.

If you can't see little things, you can zoom. If you have issue with poor contrasts, you can configure your display and/or your browser and/or your OS. If you can't see anything, you can use screen readers. If you have issues with low contrasts, you configure your computer or your browser to override contrasts.

Being "accessible" doesn't mean that your website have to think about every possible disability and that you have to provide a solution. It means that you use decent defaults styles but above all, it means that your website continues to function when it's degraded by the user agent.

Someone with eyestrain issues will not hate you because you made a bad color choice for his disability. But he will probably hate you if him changing the colors or the zooming ratio renders your website unusable.

edit : Also I have strong issues with contrasts due to amblyopia + astigmatism and this page was a pleasure to read. Black on light gray with slight font shadow is exactly what my eyes need.