Book about a man whose vision is held hostage

Hi all. This is my first time using livejournal so please forgive me if I flub this up.

I'm looking for a book I read possibly during the late 80's. It was far future science fiction.

Pretty much the only thing my addled memory can recall clearly is the opening scene:

A man wakes up in an austere hospital room. He opens his eyes and is ecstatic. He can see! A voice which he can't identify pipes up on the intercom and asks him to describe what on the table to his side. The man is gushing with happiness and says "there's a black thread laid down in a figure eight. Where are you? I want to thank you!". The voice then explains that he is not speaking to the doctor. His eyesight was not just restored, it was enhanced. The room he is in is pitch black for any normal human, but in order to keep his vision he will need drugs. These drugs will be supplied only if he does what is asked of him. If he does not obey, he will go blind again. Permanently.

If I remember right, the voice belonged to a methane-breathing space pirate who wanted the individual to spy for him on a planet that had very little light. At least that's what I remember, but that could be my mind playing tricks on me. I read a lot of books that summer and I am most likely mixing them up.

Thanks in advance!
I know that book, and that's not the opening scene, although it's close to the beginning.

I don't remember the title, but I'll try to track it down tomorrow . . .
I can't believe you found it! I've been killing myself trying to find that book for over 20 years. You've probably just added a few years to my life. Thank You!!

I don't know how you did it, but I'm truly grateful.

Oh, I've read and enjoyed that book _many_ times, though not recently! If it wasn't in a box from my last move, I'd go read it again, having been reminded . . .

By the way, although that book was credited to Carroll M. Capps, the author more commonly wrote under the name C. C. MacApp (just in case you wanted to try other books by him, although this one was my favorite).

(and thanks for the Wizard Hat! ;) )