I would consider looking up some self-relaxation methods and trying those out. Various therapies can also help improve focus. A technique known as EMDR to treat PTSD was shown to increase visual focus in a recent study, so there is a lot of research underway. From a clinical perspective, a lot of patients I've worked with were able to achieve better concentration after inducing self-relaxation methods on theirselves. It is something you might want to try!