Children's eyesight/vision - what is this strange thing???

I can remember when i was young, (under 10 I think) that when i looked at an object it seemed to become small and faraway. . I'd forgot all about until i had my own children and they've both mentioned this happening at around the same age. Does anyone know what this is? Is it just the eyeball changing shape or should i be worried. My eyesight is quite bad now i'm older and i'm wondering if this is linked?? thanks