Wonderful generational connection! I remember my parents watching me when they realized my eyes operated in much the same way as my paternal grandmother's did. I could see things almost microscopically when they were very close to my eyes. They just stood there smiling at me. Thanks for posting this.
a warm expression of genuine, reciprocal and perhaps inherited naivete–so few words to show that captured glimpse of knowledge: the girlishness of a mother and the implied girlishness of the speaker, together giving the poem its unspokenness — that we are all at once young and old and every age we've ever been in the brevity of it all. Life is one long departure, after all. (as she turns to leave) I appreciate the quiet gratitude between each line.