You are right, there are drops that sting and drops that sting more, it all depends on the procedure you're having done. I have an eye problem (not diabetic related) for which I attend the hospital for regular scans, the drops they use do sting slightly (but anything you put in your eye will sting) the consultant is looking at one particular area of my blind eye.However, when I go for Retinopathy screening the drops sting a lot....different drops for a different procedure, this time they want to see the whole area at the back of both eyes. Without the correct drops they would not see the whole area only limited, I prefer a few seconds of discomfort and a complete check up rather than a limited check which could miss a problem. As I have said previously on other posts, your eyes your decision, but you can't blame the Opthalmologist if something is overlooked, it's a personal choice which could be risky