That you feel difficult to focus on things refers that when you see things, you see double images. It may indicate that your eyes are tired, sometimes I also find it difficult to focus on things when my eyes are fatigue. Under this case, I would blink my eyes and have a rest. Or you may get double vision, which can be caused by the eye diseases or function disorder of extraocular muscles, or there is something wrong with the optic nerve, even the optic nerve center in the brain. I advise you to go to hospital for an overall ocular examination and a magnetic resonance examination of skull and hypophysis.