It means if you have at least one eye, you will see the Truth and this Truth will be the light upon you. But as it is, people are usually blind.
However, the one-eye symbol is also popular in occult symbols, freemasonry, and the despotic nation of Saudi (who also flashes a big 666 in their police cars, infamous for their human rights abuses and failure of their justice system).
The one eye actually symbolizes the chief archon - the chief of evil in our world. Because he can see the Truth and this Truth he hid from us in order to deceive us. Organizations who uses the symbol, worship this evil. The least secretive of them being the Kingdom of Saudi in the Middle East who also has 666 on their police cars and uses Freemasonry logo in their military badge! Interesting huh? Especially with the fact that they are close allies of USA whose founding fathers whom many are Freemasons!
Sigh...
And, I am not being facetious here, but it is true that the only ways to understand the intricacies of [the Word of] God is 1) through mysticism, or 2) through the Holy Spirit. The former will give you a lot of information and context, but it is disconnected from God spiritually. It is just gnosticism. The holy spirit will give full understanding only.
The eye symbolism is indeed used in occultism and mysticism. And, it does mean enlightenment, the Grand Architect (G of Freemasonry,) the Archon(s), and so on. They are graven images of spirituality, polluted by evil. But, it is not inherently bad (the verse used is about something other than the Eye of Horus enlightenment.)
A lot of books have been hidden, removed, deemed evil, lost, stolen, and destroyed. Even the Gospels say that everything Christ taught cannot fill enough books, so 30 books certainly do not give the whole of Christ's ministry. It would be sort of silly, then, to take a frozen stance on the validity of the substance of the bible since.
I don't know if I would be orthodox. I believe in a literal creation, a literal global flood, a literal exodus and parting of the sea, and so on. But, I don't believe in a rapture, and I don't think he'll is (all) fire and brimstone forever, more of spiritual burning/pain from separation from God. I dont think our generation was the smartest, most medically inclined, technologically advanced, or scientifically forward that has lived - and I am not even talking about Atlantis, or Lemuria. I also think angels mated with humans, and produced literal giants. (Just look at the ancient Greek gods... sure did love human women, didn't they? Their "demigod," not so much. Zeus and Hercules comes to mind immediately, a mimicking of the Christ, since His sacrifice was prophesied in Gen 3:15.)
But, I am also mathematician, and I often talk in allegory and imagery when explaining incredibly difficult topics - like referring to the handedness of neutrinos as a bunny running ahead of itself, and looking back. That makes no sense in real life, and if in 1000 years someone read my notes they most likely would have no idea what I was saying.
Bringing me to my first point: the only way to know would be through some sort of gnosticism, or through the Holy Spirit - that is, if I am not around to answer for myself. Unfortunately, if you do not have the holy spirit, the only way you will "know" is exhaustive, taxing occultism/mysticism/gnosis.
For example, the Star of Baal, later known as the Star of David is a flat-screen view of Metatron's Cube. The baphomet? It is the lower matrix of Metatron's Cube. Metatron's cube, like the Kabbala Tree of Life is one of many thousands of mystic artifacts that claim to hold knowledge. It is literally too much NOT in the canon to argue for its absolute perfection. God's word is perfect; a canon that has been spliced and edited by men maybe not so much.