What is the first step in performing manual lensometry or keratometry?

The first step in performing manual lensometry or keratometry is to focus the eyepiece. This step is crucial because it ensures that the examiner has a clear view of the reticle or scale within the instrument. Proper focusing of the eyepiece allows for accurate readings when measuring the lens or corneal curvature. By adjusting the eyepiece to personal eyesight needs, the technician can minimize errors due to parallax or blurriness, which could compromise the precision of subsequent measurements.

The alignment of optics, calibration of the instrument, and measuring pupil distance are important tasks that follow but do not constitute the foundational first step necessary for an effective measurement process. Properly focusing the eyepiece sets the stage for the other steps, ensuring that the operator is looking through a correctly adjusted viewfinder.