What Causes Enlargement Of An Eye In A Child?

Hello Doctor, My son is 2yr 6 months old, since his age of 6 months noticed his right eye is slightly bigger than left eyes, he has almond shaped eyed unless I say it was not obvious to others, I do not know what caused this, he is able to move his eyelids of both the eyes normally and vision no problem thankfully. Showed to his paediatrician at the age of 6 m , she said it is not obvious not a problem but in his recent photo could see the difference visibly. I am worried it should not lead to any eye problem in future. Is there any treatment to correct it what could be the reason which caused this , I used to massage during those days on his face, around eyes very softly, worried is this the reason. Please help me