adult double vision after retinal repair

Hello-I am an adult and had diplopia following retinal repair surgery on my right eye.  I had damage to both horizontal and vertical muscles.  The horizontal was the worst and the pediatric ophthalmologist operated on it-he said the lateral was close enought that it would  compensate by itself.
Eventhough he says the eyes are aligned and don't move with the prism test, my vision is still double in the vertical direction (false image up and to the right of the image from left eye) and still have the lateral displacement as well.
What I don't understand is this-I thought once the surgery was performed, if the eyes were close to alignment, then a slight imbalance would be compensated for. I understand that the alignment only holds true if I am looking straight ahead, otherwise the eyes won't sync because the muscles are never the same.
The images may fuse for about the first 5-10 seconds that I look at something, but then the vertical just starts a slow drift upwards-is more surgery needed?  My surgeon says that this is all that can be done and I need prisms-my understanding was that the muscle surgery would eliminate the need for prisms.
Can you explain?
Thank you.

[JodieJ]

I've had eye muscle surgery as an adult myself, so I'll attempt a response based on my understanding.  (In the process, I'll bump your post back up to the top of the list.)

Eye muscle surgery doesn't come with a guarantee.  No surgeon can (or should) promise a successful outcome.  In my case, I was told that there was about a 75% chance that the surgery would eliminate my diplopia, and about a 25% chance I'd still need prisms.  (I ended up in the lucky group.)  If you're unhappy with your results, by all means get another opinion from an experienced strabismus surgeon.