You could have warned which game that spoiler was related to, los. (
TMC)
I'm not sure if Aganihm's symbol is related to the others, since the Sheikah race hadn't been introduced when
ALttP was made. It may have had something to do with how many of the enemies in the Dark World had only one eye.
The Lens of Truth's design is obviously related to the
Sheikah eye symbol. The Lens is found in the well, and
Impa, a Sheikah, is responsible for the seal on the well. Also, a large stone with the Eye emblem guards the entrance to the Shadow Temple.
In the Shadow Temple, there are many portraits on the walls of a strange demon's face, which occasionally speaks to you, giving hints. Looking closely at the portrait, the shape of the demon seems to resemble the Eye of Truth design. His face is large and round, with three triangles above it, and two lines come down below it to form a shape similar to the tear on the Sheikah emblem. The Shadow Temple houses Bongo Bongo, a one-eyed demon.
I might be crazy, but there could be a link between Bongo Bongo and the Lens of Truth. The portraits in the Shadow Temple could depict the man from Kakariko with the Eye of Truth. Before the man passed away, his eye was taken and used to create the Lens. His spirit was left with one eye, and it gradually took the form of Bongo Bongo.
I'm not sure how the Sheikah would tie in to this, as we know very little of their origins. The Shadow Temple hints at Hyrule's bloody history, so maybe there was a civil war, and the Gossip Stones were used by the Sheikah to spy on all the corners of the Kingdom. During
OoT's time, the Sheikah guard the Royal Family, but in
TWW's time they could either have formed an alliance with Ganondorf or been defeated by Ganondorf, who took their shields as trophies. In Oracle of Ages,
Veran,who has an upside-down Eye emblem, seems to be a Sheikah, and she tries to revive Ganon. Aganihm speaks of a Tribe of Evil, which has the emblem of an Eye with no teardrop. I don't know if all of that ties together somehow.