The exact amount of IOL implanted in the eye during cataract surgery is calculated according to the patient’s corneal curvature and the length of the eye axis, and is not set in stone. Cataract is a common ophthalmic disease, caused by the lens inside the eyeball becoming cloudy and less transparent due to aging, trauma or medication. Patients will experience vision loss and usually require surgical intervention to replace the cloudy lens with a clear IOL in order to restore vision. The IOL implanted inside the eye has a degree, which needs to be converted according to the patient’s corneal curvature and the length of the eye axis, etc. Therefore, the patient needs to undergo a relevant examination to calculate the degree of the IOL and customize it before undergoing the surgery.