a. +3.00 / -1.00 X 180 to the base curve + 6 D b. -2.00 / +1.50 X 90 to the base curve - 6D
b. -2.00 / +1.50 X 90 to the base curve - 6D
Step one: First transpose the cylinder so that it is the same sign as the base curve. +3.00 / -1.00 X 180 becomes +2.00 / +1.00 X 90 Step two: The required spherical surface is obtained by subtracting the base curve power from the spherical power above and this give +2 - (+6) = -4 DS Step three: Specify the axis of the base curve. This is 90 degrees to the axis of the required cylinder and represent the weaker principal meridian of the toric surface. The value is: +6.00 X 180 Step four Add the required cylinder to the base curve power and this give: +6D +1D = +7.00 X 90 The complete toric formula is -4.00DS / +6.00DS X 180 /+ 7.00 X90
The complete toric formula is -4.00DS / +6.00DS X 180 /+ 7.00 X90
Step one: -2.00 /+1.50 X 90 = -0.50 / -1.50 X 180 Step two Required spherical surface is -0.50 - (-6) = +5.50 DS Step three: -6.00 DS X 90 Step four: -6.00 + (-1.50) = -7.50DS X 180 The final toric formula is +5.50DS / -6DS X 90 / -7.50DS X 180
The final toric formula is +5.50DS / -6DS X 90 / -7.50DS X 180