Can a doctor measure wrong prescription of a patient and operate for the wrong prescription in lasik? How do surgeons make sure that they have programmed the machine exactly as per the patient eye! Because they measure refraction by subjective tets so there always a possibility of an error. I have my surgery due in July at AIIMS , Delhi, I have astigmatism but I am afraid if the surgeons operate for my wrong astigmatism axis/ wrong prescription. Please tell how so surgeons avoid these "human errors " in calculating eye power as patient eye prescription may change just before the day of surgery by a small amount! Do surgeons check eye power once again just before  the surgery ? ( on the surgery day) ?