Thanks for all your responses and encouragement. Things are looking better for my friends eye (no pun intended), but probably not fast enough for him to play in league playoffs :frown:. Although long term is what we were really worried about.
Sounds like one eye isn't really a problem in itself, but adjusting from two to one eye may not be a quick thing. (I bet going from one eye to two eyes would be really tough!)
We'll try some things out today....I think the advice to try to stick to one table size makes a lot of sense and I had really thought about that.
If we come across any drills that seem to help, I'll report back.
The nice thing about pool for a monocular player is that, unlike in other ball sports, the cue ball is (1) constrained to move on a flat surface, and (2) not in motion when you strike it. Depth perception becomes less of a factor.
How did you friend first learn to aim? One option would be to revisit those initial aiming drills and relearn aiming. When your friend aims, what does he think of: the contact point? or the amount of ball "covered" by the cue ball (e.g. half-ball hit)? or some other method?
If your friend gets frustrated trying to repeat his success with his old aiming method, then he might just try a different approach to aiming. Heck, even Tiger Woods rebuilt his stroke.
Bob Fancher's Pleasures of Small Motions--the best book I've found on the mental game of pool--could help your friend find the proper approach to relearning aspects of the game.
Curious to hear how your friend does. We one-eyed and lazy-eyed players will root for him.