[fbr]

> There's a specific reason why they do this and ask you to make a decision in an instant. It's called accommodation. Your eyes will quickly try and accommodate and find focus if they're allowed to stare too long. This could explain the reason he got such different results from the exams. He was trying too hard. Just follow directions.

I don't have a long experience with glasses but I have never received these instructions and my experience is similar to the author.