وَاجِفَة (tremble): Disturbed and frightened due to the enormity of the Day of Judgment. Allah (swt) explains the state of the hearts. However, do hearts have sight?
Yes, they do! This is as Allah (swt) mentions:
﴾فَإِنَّهَا لاَ تَعْمَى الأَبْصَارُ وَلَكِن تَعْمَى الْقُلُوبُ الَّتِي فِي الصُّدُور ﴿
(..Verily, it is not the eyes that grow blind, but it is the hearts which are in the breasts that grow blind.) (Al-Hajj: 46)
The humbling of the eyes here indicates the actual content of the hearts and the fear found in them.