News Here are a few common mistakes made when using a manual lensometer and ways you can improve your practice

Mistakes

1.Failing to properly focus the eyepiece:

If the eyepiece is not focused to the examiner's eye, it can lead to inaccurate measurement of power.

2.Incorrectly positioning the lens:

If the lens is at the wrong angle or not properly centered on the reticle it can cause errors in both axis and power measurements.

3. Not compensating for calibration errors:

If the lensometer is not properly calibrated to read 0D with no lens, then the measured powers will be inaccurate by the same amount.

4. Misinterpreting principal vs spherocylindrical powers:

Lensometers measure these two principal powers, which then need to be converted to sphere, cylinder and axis. Failing to do this conversion correctly can lead to 90° axis errors.

5. Not verifying against the original prescription:

Checking the lenses against the lab invoice rather than the doctor's original Rx can miss 90° axis errors made by the lab.

So in order to get the most from your equipment

1. Always focus the eyepiece:

Before each use, carefully focus the reticle by looking through the eyepiece and adjust the diopter ring.

2. Properly position and center the lens:

Align the 180° axis line parallel to the reticle and adjust the lens until the target lines cross at the center.

3. Periodically check calibration:

Ensure the power wheel reads 0D when no lens is present, by focusing the target. Compensate for any error in future measurements.

4. Understand principal vs spherocylindrical powers:

When measuring a spherocylindrical lens, take two readings 90° apart. Convert these to sphere, cylinder and axis.

5. Always verify against the original Rx:

Check the lens against the doctor's prescription, not the lab invoice, to catch any 90° axis mistakes.

By following these best practices, you can minimize common errors and ensure the most accurate lensometer measurements to provide your patients with precisely fabricated eyeglasses.