My daughter had her sight test and they're a little worried she failed the 3D test - why would this be?

You know the test...it's the one where your child puts on the funny gles and has to point out which items 'stands out' in the book they are given. The optician kind of also implied my daughters eyes were not working together properly as they should be. She has to go back and have special drops put in her eyes so they can take a better look. She has just turned seven by the way. I was a bit flustered to ask whilst I was there. Any opticians out there that could give me some idea of what's going on or parents that have gone through a similar thing with their child? Thanks for taking the time to read this - much appreciated