Why is it that i do poorly on visual field test using a frequency doubling perimetry machine but test results are much better using humphrey machine.

Complex question.: This complex question is best answered by an Ophthalmologist (one who knows your condition & knows you best). In general, there are 2 types of perimeters (devices which measure visual fields). There are kinetic perimeters, like the frequency doubling machine, & the static perimeters (like the Goldman method, Humphrey machine, & Donder's test). If you can't see flickers, you do worse on kinetics.