Could have been a fluke.

Interocular pressure can increase, sometimes suddenly, and can lead to damage of the visual nerves and blindness (that's called glaucoma). It is easily treatable with meds, but you generally have to stay on them forever.

It is more typical in older people, so I would probably get re-tested a couple of times and then go to the DoD and ask for them to test you again. I don't think it really varies from day-to-day so if you test OK a few times, you should be good.