I have had this kind of eye-ache upon awakening before, though not often. I think it is caused by having had too much "rapid eye movement" sleep the night before. As you know, during the phase of sleep that includes dreaming, our eyes are darting about very quickly. If you have had several days and nights' worth of deprived sleep (not enough hours), or your sleep has been interrupted rather than continuous, you may acquire a kind of REM-sleep-deficiency. On the night that you finally *do* get enough hours of non-interrupted sleep, your brain "catches up" on all of its REM sleep in the same night. Experiencing that many hours' worth of constant, rapid eye movement leads to the kind of eye-ache you described, when you first awaken the following morning. Thus, the only way to prevent it is to get higher-quality sleep every night; but once you have the eye-ache, an acetominophen tablet should help.