Actually when you have the retinal detachment, you will have nothing to feel. It is true. However, you should know it and go to the hospital to accept the treatment as soon as possible. Or else, your eyes may get blinded. You should take this problem into serious care. You should accept the surgery which will be safe and effective.
In the first place, so sorry to hear that your classmate has got retinal detachment. So, generally speaking, retinal detachment would give rise to a dramatic decrease in the vision , thus causing a lot of troubles in seeing things clearly. However, typically, retinal detachment does not generate painful feelings. Maybe there are less nerves connecting to the brains. However, it is one of the most terrible situations we might run into.