There are several reasons for keeping your eyes open when you practice meditation. With your eyes open, you are less likely to fall asleep. Then, meditation is not a means of running away from the world, or of escaping from it into a trancelike experience of an altered state of consciousness. On the contrary, it is a direct way to help us truly understand ourselves and to relate to life and the world.
Therefore, in meditation you keep your eyes open, not closed. Instead of shutting out life, you remain open and at peace with everything. You leave all your senses — hearing, seeing, feeling — just open, naturally, as they are, without grasping after their perceptions.
Whatever you see, whatever you hear, leave it as it is, without grasping. Leave the hearing in the hearing, leave the seeing in the seeing, without letting your attachment enter into the perception.
from the book “The Tibetan Book of Living and Dying”