Find the approximate power in the 90th, 180th, 45th and 122nd meridians.
This power will not be recorded in the wearer's records or ordered from the lab.  It is a step in doing prism problems.  Therefore, it will not be rounded to 1/8 diopter steps;  it will be rounded to two decimal places.

Do this set using the formula and your calculator.
 

	90th	180th	45th	122nd
1.  +3.50 2.  -1.00 -1.00 x180 3.  +0.50 -2.00 x030 4.  -1.00 +1.00 x080 5.  -1.00 +3.00 x110 6.  +8.75 -2.25 x005 7.  -16.75 -2.00 x179 8.  -16.75 +2.00 x005  9.  -0.75 +1.00 x092 10.  -1.62 +1.75 x115 11.  +0.25 -0.50 x135 12.  pl -0.50 x058 13.  -4.25 14.  pl +3.75 x053 15.  +0.25 -0.50 x145 16.  +0.25 -0.25 x135 17.  +22.50 -3.50 x058 18.  -0.25 -0.50 x033 19.  +1.00 -2.00 x090

Find the approximate power in the 90th and the 180th meridians.
This power will not be recorded in the wearer's records or ordered from the lab.  It is a step in doing prism problems.  Therefore, it will not be rounded to 1/8 diopter steps;  it will be rounded to two decimal places.

Do this set using the shortcut, without your calculator.
 
 

	90th	180th
1.  +2.50 -1.00 x030 2.  -3.25 +2.00 x135 3.  pl -2.00 x 150 4.  +3.00 -3.00 x045 5.  +3.00 -1.50 x060 6.  -5.00 7.  -1.25 -1.00 x180 8.  +2.00 -4.00 x120 9.  -1.00 +4.00 x060 10. +12.00 -2.00 x090

The answers are here.  Please do them yourself before you go to the answers.  If you understand it all and you don't need the practice then it will only take you a few minutes to do them.  If you are struggling with the formulas do one or two, check them, do a few more, check them, . . . just make sure that you do not look ahead of the ones that you did and are checking.