Dad had a glaucoma surgery a month ago and had hyphema since then and his doctor still tell him to wait cz his pressure is low and blood is far?

Hyphema : As long as his postoperative course is being closely monitored, appropriate interventions will be performed. Post-glaucoma surgery hyphemas may occur, as a result of creating an opening in the white part of the eye. These usually resolve with time and medical management. Ocassionally a procedure is performed to wash out the blood. As the iop is low, a cautious wait period is acceptable.

Waiting can be good: Depending on the severity of the low pressure it may be too dangerous to remove the blood, and given that most blood clears up on its own, your doctor may have recommended observation.