Lens Implants
Lens implants are necessary to replace the refracting ability of the natural human lens. Long ago, people had to wear thick glasses or contact lenses after cataract surgery when implants were not available. Prior to surgery, the doctor uses and A-scan and Keratometer to measure the length and curvature of the eye, so that a precise calculation of implant power can be made. After surgery, one needs to change his glasses since the implant changes the prescription. The new prescription will fine tune your vision.
Also see Intraocular Lens (IOL)