To clarify for future reference can you assist?

A free kick is awarded, however prior to the free kick being taken the defending team have a player who has some dirt/mud in his eye. The player is on his knee whist the players request assistance from the trainer however the trainer does NOT enter the field of play, instead the defending teams goalkeeper assists in removing the mud/dirt and the defender is then able to continue playing, however the referee speaks to the player and insists that the defender leaves the field of play as he has received treatment is this correct?

I have seen players assisting others who have cramp etc and I have never seen the referee send them from the field of play.

Answer (March 10, 2013): BELATED POSTING
According to the Interpretation of the Laws of the Game and Guidelines for Referees (in the back of the Law book), “a player is not allowed to receive treatment on the field of play.” However, “treatment” in this case means that someone has entered the field to administer to the wants and needs of the player. If someone is authorized to enter the field temporarily and quickly for these ministrations, then the player must leave when they are completed and may not return until the match has restarted and he has the referee’s permission to re-enter.

If, as in your situation, the referee has not stopped play for the problem (not exactly an injury) and has not beckoned any other person into the field to treat this problem, and no one is discommoded by the goalkeeper’s kind act, then the player does not have to leave the field. Unless (1) the treatment consumes an inordinate amount of time or (2) there is some local rule or rule of the competition that specifically prescribes an exit from the field, just as in cases of cramp treated by fellow players already on the field; the referee simply adds time lost.

Some referees remember only those parts of the Laws that they may require for their own convenience.