If the sphere lines are focused and unbroken at -1.00, axis 100, and the cylinder lines focus at -1.50, how would the prescription be recorded?

• A. -1.50-1.00X100
• B. -1.00-0.50X100
• C. -1.00-0.50X90
• D. -1.00-0.75X100

Answer: (B)

This asks how to record a glasses prescription with sphere and cylinder/axis. The sphere value (-1.00) is the power in the meridian with no cylinder. The cylinder power (-0.50) is combined with the sphere to give the power in the meridian perpendicular to the axis, so that meridian has -1.50 (since -1.00 + -0.50 = -1.50). The axis (100) tells you the orientation of the cylinder, i.e., which meridian is left uncorrected by the cylinder.

So the correct notation is -1.00 -0.50 x 100.