outer canthus; outer corner of the eye
目尻にしわが増えてきた。
Wrinkles have been increasing at the corners of my eyes.
彼女は目尻を下げて笑いかけた。
She smiled with the corners of her eyes crinkling.
疲れると目尻が下がり、眠そうな顔になる。
When you're tired, the outer corners of your eyes droop and you look sleepy.