What is the first step in performing lensometry or keratometry?

The first step in performing lensometry or keratometry is focusing the eyepiece. This initial adjustment is crucial because it ensures that the practitioner sees a clear and sharp image through the instrument. Without proper focus, any subsequent measurements taken will be inaccurate, as the clarity of the optical system directly impacts the precision of the data obtained.

Focusing the eyepiece allows the technician to see the target or lens clearly, which is essential for accurately determining the power of the lens being measured or the curvature of the cornea. It ensures that the readings taken from the device are reliable, which is fundamental in fields like ophthalmology where precise measurements inform assessments and treatment decisions.

While other steps, such as aligning the lens or positioning the patient, are also important in the overall process of lensometry and keratometry, they are secondary to ensuring the eyepiece is properly focused first. Calibrating the device is a maintenance step that should ideally be performed before testing begins but does not directly pertain to the initial procedure.