A cataract develops when the natural lens inside the eye becomes cloudy. It can develop in people over 55 years of age and is part of the ageing process. The cataract is removed by a process called phacoemulsification surgery, where the cataract is broken up using high-speed ultrasound waves and then removed. Then an intraocular lens is implanted into the lens capsule to allow the eye to focus. Lens implants come in different types and strengths and the ophthalmologist will determine the optimal lens choice with the patient before surgery.