Toddler with glasses

 My son is 21 months old and I'm having the hardest time getting him to keep his glasses on his face. He always pulls them down and wears them like a necklace or pulls them to his mouth, which he eventually ends up eating off a nose piece! Ive tried reading with him as the eye doctor suggested and making them loose so they dont hurt him. It just seems that he just has no interest in wearing them, which he obviously needs them because he goes cross eyed and nearly runs into walls without them, I just am having no luck he hates them and not to mention he has the LONGEST eyelashes ever! Any advice is appreciated