This condition of congenital nystagmus is never going to get cured however L V Prasad Eye Institute is one of the best institutions in the country and they must have explained the situation to you.
When they did the operation they intended to reduce this condition and also try to improve the vision in the process, not cure it.
Doctors are not gods and can only do so much and cannot cure all problems.
One good thing about your nystagmus is that although your distance vision is not so good but your near and reading vision is reasonably good so that you can study as much as you like.
I would advise you to choose a career or profession where vision requirement is not crucial.
What I want you to remember that there are lots of people who are much worse than you even in western countries and they lead a nearly normal life. You may know that even the home minister in the UK government was completely blind from birth and he educated himself and is still a very clever man. Never accept defeat and get upset or think of dying.