A clouding of the cornea, most common in older people, but not unheard of in people under the age of fifty. It is usually caused by a buildup of proteins in the cornea that occurs in aging, but trauma to the cornea (such as a blunt hit by a ball) can cause cataracts in younger patients

The surgery most often used to remove a cataract is phacoemulsification, a type of microsurgery in which an incision is made and a device is used to suction the inside of the cataract. Recently topical anesthesia (using lidocaine gel) in addition to a benzodiazepene (like Valium or Versed) has been used to numb the eye, although sometimes a block (more potent anesthesia using a syringe) is required. After the surgery, an intraocular lens implant(IOL)is sutured (stitched with a microscopically fine thread) over the the eye, and the benign shell of the caract is left to speed recovery.

In some cases, after a phacoemulsification surgery, residual proteins from the cataract will build up and a follow-up surgery will be required. Most frequently, no scalpel is required the second time, and the buildup can be adequately eliminated with a low-intensity YAG laser.