Question

You are using the lensometer to read the power in a lens in which the three sphere lines become clear with the power drum reading +1.25 and with the axis wheel reading at 138. Moving the power wheel, the three-cylinder lines come clear at a power drum reading of -4.00. Which of the following would be the correct prescription from this lens? Select one: +1.25 -5.25 x 138 -4.00 +1.25 x 138 +1.25 -4.00 x 138 -5.25 +1.25 x 138 ​

Answer 1

The correct prescription from this lens would be +1.25 -4.00 x 138.
The first number, +1.25, is the sphere power of the lens, which is the power drum reading when the three sphere lines become clear. The second number, -4.00, is the cylinder power of the lens, which is the power drum reading when the three cylinder lines become clear. The final number, 138, is the axis at which the cylinder power is oriented, which is the reading on the axis wheel when the three cylinder lines become clear.

Answer 2

The correct prescription from this lens would be: +1.25 -4.00 x 138

Step-by-step explanation:

This is because the power drum reading of +1.25 represents the spherical power of the lens and the -4.00 represents the cylindrical power of the lens. The axis wheel reading of 138 represents the axis of the cylindrical power. The correct prescription for the lens is written in the format of spherical power, cylindrical power, and axis.