For about the past 2 months now, I tend to get double-vision, but only in the afternoons. It is accompanied by a "tired" feeling, but I use the term tired loosely as I am not actually physically tired. No matter how hard I try to uncross my eyes and focus clearly I cannot. This is almost every day, and between the hours of 2pm-4pm. I do office work and do stare at a computer screen all day, could this be the cause? Any suggestions? I have also been experiencing neck/thoracic pain between the shoulder blades with tightness and cracking joints through those areas of the spine.