The simplest answer is usually the right one

... and the most often overlooked! I had a rather fun experience in clinic today where I couldn't get a kid to see clearly out of one eye behind the lens machine, even though I knew he could see without it. Funny thing, you'ld have thought I would have pulled the machine away to see if there was something wrong with it, and I did everything to it, except put my head in it and look through it, but I didn't, so I spent a ton of time trying everything I could think of to get this kid to see, and finally through my hands into the air and asked the attending for help, first thing she did was check the machine, and sure enough, even though I had just used it on a previous patient, it was messed up somehow. So moral of the story, don't go looking for complex answers until you've ruled out the simple ones. And yes I made a complete clown of myself re-learning this!