ALCON HAND HELD AUTO-KERATOMETER Measuring Technique Start by pressing the large measure button once to turn the instrument on. (If pressing the measure button does not turn the instrument on, simultaneously press the measure button and the top center select keys-this is called a hard reset) Press the appropriate eye button below the measure button for the eye you will measure. There will be a dot in the center of the eye icon on the display window indicating the eye the instrument is set for.