Deep meditation can lead to a disconnect from the body, where one loses track of it completely due to utter absorption in the meditation object. I think what happened was, you opened your eyes before the reconnect was established.
Whether or not this is sound practice, well, I really have no idea. Did you find it beneficial?
Yes, when I opened my eyes I brought my meditation to a close. Although I had been diligently practicing samatha for over a week, at the time I was rather young and knew practically nothing of the Dhamma. On the following day I was very acutely aware of the loathsomeness of the body and I recognize now that this would have been the very time to begin vipassana meditation.