Hello I Had Open Hart Surgery Close To 4 Years

Hello I had open hart surgery close to 4 years ago and was left partially blind. I was told that it would return but did not. The problem that am having is that before the sergury I was told to sign a paper which today I know it was for research something to do with high blood pressure test? I really believe if this test was not done I would have my vision in tact what do you think?