Is it serious to temporarily lose depth perception?!

I just lost my depth perception. This has been an on-and-off thing with me for a couple years. It seems to happen whenever I have either been reading a lot, or when I am stressed out. As I type this, I can't tell how big anything is or how far away it is.. it'll most likely go away by morning, but it's very annoying. It only happens once or twice a year. Is it very serious? Is it perhaps due to stress?