Josh de Lioncourt, for Macworld:
iOS 7, in general, has been a challenge for low-vision users. Many of the stylistic choices such as transparency and lack of contrast and clearly defined buttons have made iOS difficult for some to see. This is made more challenging because vision is so variable. What works for one low-vision user is unlikely to work for another.
Apple has begun to address this in iOS 7.1 by adding button shapes, more contrast options, and expanding some of the existing options—all found by choosing Settings > General > Accessibility. In general, this is a significant step in the right direction, but there is still much to be done.