Dax just the way he roll.

Slow to respond back here, but... these are what I've come across as explanations.

1. A punch in the eye as punishment for transgressing some code of honor.
2. A punch in the eye as part of an occult ceremony. (The Freemasons have rituals that purportedly involve body strikes.)
3. Violent butt rape, to quote Rardog900. Possibly as part of an initiation ceremony. (But then why not both eyes? Reference the disgusting Panda Eye Club.)
4. Surgery to insert neurotransmitters and/or artificial neural networks behind the retina for monitoring and control. As in: we see everything you see.
5. Surgical replacement of the eye with an artificial eye, possibly with tech mentioned in 3.
6. Vril parasite dropped into the eye. Like the miniature scorpion critters from Star Trek's Wrath of Kahn, but dropped into the eye instead of the ear canal.

I've ordered this list of six from most prosaic to most esoteric. I don't rule out the Vril explanation. The pre-WWII Vril Society is a pretty wild rabbit hole. But what I've read does not cross over the threshold into "yeah that's definitely it". I've yet to see anyone present a biology textbook full of measurements, drawings, and photographs detailing the life stages and reproduction of supposed Vril parasites. Which would be how the mind-controlling Vril want it, right?