What is the first step in verifying a prescription with a manual lensometer?

The first step in verifying a prescription with a manual lensometer is to focus the eyepiece. This is crucial because proper focusing of the eyepiece ensures that the operator can accurately read the power and axis of the lens being measured. If the eyepiece is not properly focused, the measurements obtained may be unclear or inaccurate, leading to errors in interpreting the prescription.

Focusing the eyepiece adjusts for the individual vision of the operator and allows for a sharp image of the lens prescription. Once the eyepiece is focused, the operator can then proceed to adjust the light source, set any prism measurement if applicable, and inspect the lens for scratches if necessary. However, these steps rely on having a clearly focused view of the lenses being tested.