Why does it say "Aleinu"?
Radak: The Navi includes himself amidst Klal Yisrael.
Malbim: When the lamenters will take counsel with the Chachamos, they will cease lamenting the dead, and rush to lament us (the living), like one rushes to heal a dangerously ill person.
Why does it say "v'Seradnah Eineinu Dim'ah"?
Radak: We will cry due to the voice of the lamenters and eulogizers. It is as if it says b'Dim'ah; Seradnah is Po'el Omed (the action applies only to the subject). Amidst [excessive] crying, it is as if the eye melts and descends in tears. The same applies to "Eini Yordah Mayim" (Eichah 1:16).
Radak citing Targum Yonasan: Our eyes will send tears.
Malbim: When our eyes are open and we see the dead, we cry. When we close our eyes and 'see' (ponder) what will be our end, they will flow a great quantity or water, not mere tears, for death is better than a life of such disgrace.
What are "Af'apeinu"?
Radak: The pupils 1 of our eyes. The matter is repeated in different words.
Radak citing Targum Yonasan: Our eyeballs.
Malbim: Our eyelids.
In Tehilim (77:5), Radak explained that Af'apayim are eyelids. He holds that the word can mean either, based on context. (PF)
