Definition of "sightless"

And yet it was possible he might love her—love her truly and deeply: if so, of what avail would it be to lower him in her esteem? It were best for Lucy still to gaze with sightless eyes on her idol.

1834, L[etitia] E[lizabeth] L[andon], chapter III, in Francesca Carrara. […], volume III, London: Richard Bentley, […], (successor to Henry Colburn), page 19

In his return, arriving at a rising ground, a knoll, he heard a rustling of the leaves in his front: an enemy was suspected ; he gathered his men around him, each taking his tree. The enemy was sightless to Boyd, and his party, yet the approach around him was sensible to every one.

1812, John Joseph Henry, An accurate and interesting account of the hardships and sufferings of that band of heroes who traversed the wilderness in the campaign against Quebec in 1775, William Greer, page 201

The toiling world is sightless to those who cannot see.

1908, The Summary, volume 36, page 72