The Eye was a giant, flaming, sentient eyeball!
The actual title of the strip was "The Eye Sees..." and no origin was ever given to the character, but the implication was that The Eye was an extradimensional or extraterrestrial entity, not a human ghost or reincarnated spirit like The Spectre or Captain Trumph, as he (it) didn't really understand human behavior, but was obsessed with the concept of justice, working hand in...whatever...with private eye Jack Barrister in dispensing it.
Like The Spectre, The Eye had near-infinite abilities including being able to warp and alter time and space, although he (it) usually limited him (it)self to generating heat rays or a searchlight beam, grow or shrink, fly, and teleport just about anywhere.
He (it) appeared in every issue of Keen Detective Comics from #16 onward to the end of the run, sometimes as the cover feature.
Then, he (it) was given his own title, Detective Eye, for two issues, ironically featuring fellow hero Air Man on the first cover and Jack Barrister (without The Eye) on the second!
We at Atomic Kommie Comics™ have revived The Eye as part of our Lost Heroes of the Golden Age of Comics™ line, on t-shirts, messenger bags, mugs and other kool kollectibles!
While he (it) hasn't been included in Alex Ross' Project SuperPowers as of yet, we think we'll be seeing him soon!
So keep an eye out for...The Eye, because he (it) will be watching you!