Se le llenaron

Question

Cómo explicarías "le" en la siguiente frase?Es "the accidental se'?Sus ojos se le llenaron delágrimas.

Answer

Hola Paul
That "le" is an indirect object pronoun referring to the person affected by it: him/her
This is called "dativo de interés" and here's a lesson about it. 
I hope it helps.
Saludos
Inma