eye problem in new kitten

I recently brought home 2 kittens about 11 weeks old. One of the kittens has an eye problem. The eye is a medium color brown and the 3rd eye lid is stuck half way over her eye. I took the cat to the vet and he prescribe amoxicillian and eye drops. This was one week ago and there is still no improvement. I know it is possible that she is blind in this eye but I can't figure out why the eye lid is like that. No drainage or anything comes out of it. The other eye is healthy. Any ideas would be greatly appreciated. She is a wonderful and sweet cat and I would like to see her perfectly healthy.

I'd take her back to the vet or get a second opinion.