A lensometer's target lines become sharper as you adjust the focus. What does this indicate?

Adjusting the focus on a lensometer and observing that the target lines become sharper indicates that the eyepiece is correctly adjusted. In a lensometer, the focus must be aligned properly to ensure accurate readings of the lens prescription. When you see the target lines increasing in sharpness as you adjust the focus, it confirms that the adjustments are bringing the lens into clear view, which is crucial for obtaining precise measurements.

Ensuring that the eyepiece is correctly adjusted is fundamental for accurate assessments during the lensometry process, as it directly affects how well the lens is visualized and the resulting accuracy of the power readings taken from the lens.