the power of a refractively ametropic eye is 58D along 90 meridian and 62D along 180 meridian. what is the power of the spectacles used to correct this patient if the vertex distance is 12mm?

a)+2.00/-4.00 x 180

b) -2.00/-4.00 x 90

c) -2.00/-4.00 x 180

d) +2.00/-4.00 x 90