Occasional inability to focus.
Very rarely (happens maybe once every two to three months) I get a about of... I don't even really know what to call it, but for some reason my eyes can't focus together and it makes it impossible to see clearly, and a headache sets in within seconds. Holding my hand over either eye works, but I just can't understand why my eyes would be unable to focus together on something for any reason. This doesn't last long but I'm afraid it may be a sign of something bigger. Any ideas? Any help is appreciated.