The picture moves in and out of focus as the machine takes readings to determine when the image appears on the retina. One eye at a time they look into the machine at a picture inside. Converting A Glasses Prescription To Contact Lenses Tutorial Part 3 Contacts Advice Prescription Contact Lenses Contact Lenses Eye Prescription UNK the. . The patient takes a seat and places their chin on a rest. The corneal shape measurement function measures the radius of corneal curvature corneal refractive powers the direction of the steepest meridian and the amount of corneal astigmatism. - -- --- ---- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- -----.