I Get Double Vision In Both Eyes (if One Eye

I get double vision in both eyes (if one eye is closed the other still sees double) of lights, small text, and very thin objects (straws etc) but only if I look directly at the light/object for a couple of seconds and it is not a complete double but an overlap, so 50% or more of the image is copied to below the original. Is this a sure sign of keratoconus or can it just be a part of regular strong astigmatism? I ask because I wish to join the US Navy.