In this device, ultrasound is used, and the sonar sensor is placed directly on the cornea after using an anesthetic drop. Before imaging, an Instocaine drop is poured into both eyes to numb the surface of the cornea. It is necessary to measure the strength of the cornea or chromatometer before performing the A-Scan method. At first the doctor enters the information and the patient's eye chromatometer into the device. After confirming the anesthesia of the cornea, the sensor is placed directly on the surface of the cornea. After at least 5 times the axis of the eye ball is measured, the lens strength inside the eye is calculated. This accurate measurement is done to determine the correct strength of the lens that was placed inside the eye after the cataract surgery